Casting Session, NOE 310-165-FN (30 XCB)
- Thread starter Idaholewis
- Start date
Idaholewis
Active Member
I deleted the footage from my camera when i got home, These YouTube Videos Take FOREVER to upload, I Don’t even have the Target anymore. I have a Binder Style Handload Log Book on my ReLoading Bench that i Write in, When i Run Across stuff that Don’t work for me (Good or Bad) it gets logged in as Such.
I ran the Same 40 Grains of Varget with the Lyman 311299 Bullet, Velocity was 2,340 Fps, It literally painted them on the Target. It IMMEDIATELY made me Question the Validity of the Thread i linked on that Bullet? Supposedly shot out to 700-800 Yards or more? with Velocity of 2,350 Fps??? My Velocity was RIGHT THERE, But my Group at 70-80 Yards was more like a Shotgun Pattern
I Understand there are Many Variables, But i stil Question that now? The Little 30 XCB on the other Hand is moving another 100 Fps Faster, and it Shot VERY Well for me, Both Bullets poured from the Same Pot of Alloy, and Water Quenched TogetherI am determined to try and make the Lyman 311299 Bullet Shoot, I Figure my next outing i will Drop the Charge 5 Full Grains (35 Grains Varget) That “Should” Get me in the 1800-1900 Fps Range? This was just before i tried them. The Lyman is a Good Looking Bullet, i hope i can get it to Shoot
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Lewis, I shoot them in an 03-a3 and always had 1 or 2 flyers out of each 10 shot group, I changed to the 314299 .303 nose vs .300 nose they just scuff the tops of the lands, and the flyers went away, but I am not shooting near the speed you are, they are for military bench rest matches at 100 yards
Bill
Bill
"Jam" means different things to different folks.....
It does EXACTLY the same thing with barrel vibes.
So,just like two guys,a country apart may agree on what jam means to them.... so can two different loads. That however,dosen't mean everyone agrees on the amt of,depth/engagement = jam. That also doesn't mean just because @X amt of velocity/pressure, this amt of jam shoots lights out....... that the same amt of jam or preload is optimized for a different load or tune.
Just sayin,am sure y'all know this. But it bears repeating. Learning what the rig "likes" in the form of jam/preload is very valuable info.
"Generally" factory barreled and chambered R700's like hard jams if you're looking for bughole groups. That doesn't mean it's the only path,just what I've observed from a dz or more of them. And "hard" here means about ripping the bolt handle off.
There's something to be said for "running" a bolt gun..... to borrow from the tacticool vernacular. In the case of BR rigs it's shooting dang fast so as to get all the bullets on target before conditions change. That works great. BUT,it also builds muscle memory. Learn to run a R700 bolt smooth,but press the envelope on actual bolt speed. Dry fire,on the clock and keep at it until you can predict the speed. Now,when you're faced with running a CB in there....really hard,you'll see the effect. Takes some practice and holding your tongue just right. Uhhh,and you can forget live round extraction at this point. Good luck with your project. BW
It does EXACTLY the same thing with barrel vibes.
So,just like two guys,a country apart may agree on what jam means to them.... so can two different loads. That however,dosen't mean everyone agrees on the amt of,depth/engagement = jam. That also doesn't mean just because @X amt of velocity/pressure, this amt of jam shoots lights out....... that the same amt of jam or preload is optimized for a different load or tune.
Just sayin,am sure y'all know this. But it bears repeating. Learning what the rig "likes" in the form of jam/preload is very valuable info.
"Generally" factory barreled and chambered R700's like hard jams if you're looking for bughole groups. That doesn't mean it's the only path,just what I've observed from a dz or more of them. And "hard" here means about ripping the bolt handle off.
There's something to be said for "running" a bolt gun..... to borrow from the tacticool vernacular. In the case of BR rigs it's shooting dang fast so as to get all the bullets on target before conditions change. That works great. BUT,it also builds muscle memory. Learn to run a R700 bolt smooth,but press the envelope on actual bolt speed. Dry fire,on the clock and keep at it until you can predict the speed. Now,when you're faced with running a CB in there....really hard,you'll see the effect. Takes some practice and holding your tongue just right. Uhhh,and you can forget live round extraction at this point. Good luck with your project. BW
Bret4207
At the casting bench in the sky. RIP Bret.
It's all about FIT! I still remember the day Felix Robbins (RIP) made the distinction between "Static" fit and "Dynamic" fit. It was like one of those "EUREKA!!!!" moments in the movies or comics. All I lacked was the light bulb over my head. Everything in this game is about fitting a specific bullet to a specific gun. That doesn't simplify any of it, but it gives you some starting points. I threw a big mess of theories and "rules" out the window the second he did that. The search for rock hard lead ended as did the search for a magic lube or case filler/buffer, barrel treatment, etc. You have to treat this like a benchrest match shooter working up a new load. A lot of us are happy with the "Low Node" stuff,but getting up in the 2500fps area is a whole 'nuther ball game.
If I could give just one piece of advice to anyone getting into this, it's WRITE DOWN any and all changes you make. I wish I was a note taker, I'm not. I often have to relearn the same lesson multiple times. More organized minds than mine have done this and thought out some step by step answers. The guys that have done that and put it down on paper are to be thanked!
Very few if us ever show pics of the lousy targets. You get the occasional guy that will post a pictorial of his groups going from nasty to "holy crap!" tight. Love those when they include the details of what he did to change things!
L Ross, yeah, the anti-LE tone over there isn't just allowed, it's encouraged!
If I could give just one piece of advice to anyone getting into this, it's WRITE DOWN any and all changes you make. I wish I was a note taker, I'm not. I often have to relearn the same lesson multiple times. More organized minds than mine have done this and thought out some step by step answers. The guys that have done that and put it down on paper are to be thanked!
Very few if us ever show pics of the lousy targets. You get the occasional guy that will post a pictorial of his groups going from nasty to "holy crap!" tight. Love those when they include the details of what he did to change things!
L Ross, yeah, the anti-LE tone over there isn't just allowed, it's encouraged!
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Idaholewis
Active Member
L Ross, and Bret4207, I was a Part of that Place as well, I see that some of us have the Same wording under our names their 
Idaholewis
Active Member
I got the “PERMA” Title
Which is PERFECT with me. I did nothing wrong, I would do the SAME thing Today, Tomorrow, ANY Day, So i guess i was “Doomed” From the Start. I wouldn’t go back there if i were begged to. I RARELY ever look on it, The few times i do is usually from a Search that leads there.
Rick H
Well-Known Member
About the note taking.....I do take notes, all sorts of them, the problem I have is I don't write down the stuff I should. I go back through my notebook and logs and invariably I ignored writing down the information I am now interested in....a lot of other useless (or mostly useless) stuff but not the stuff I need now.L Ross, and Bret4207, I was a Part of that Place as well, I see that some of us have the Same wording under our names their
Idaholewis
Active Member
I use to be HORRIBLE about keeping Good records, But owning a Large Gun Safe PACKED with Muzzleloaders, and a Tote Full of Bullet Molds, I had to MAKE MYSELF start keeping better Records, I do so much with them from Grease Groove to Paper Patch, I couldn’t remember what i had done, or hadn’t done? I stil catch myself not keeping good enough Records, Sometimes I can’t decipher my own Notes?
I even keep Notes with Certain Bullet Molds
Ian
Notorious member
Dang, Lewis, the "PERMA" is a true distinction. I though Bret was the only one to get that. Funny, a little scene starting Billy Crystal always plays in my head when the perma-banned thing comes up. Is that like being pronounced dead, then being run through a meat grinder, burned, and the ashes scattered across seven continents? I'm actually disappointed that I didn't get the perma-banned title, if ever there was someone they wanted gone for ever and his memory erased from the board it would have been me. And I was the last Golden Bullet Award member before I leveled both barrels of the Reason Blaster on the owner and got the boot.
Those 311299s shot just ok for me out of my '06 at 1950 fps using a dirty, slow load of H4350. For some reason (probably the nose being fatter) the Lee 312-185 at the same speed did better and had no flyers. That was my go-to deer whacker for quite a few years, 1.5 moa for ten shots from field positions in any weather, any temperature I encountered, on any given day of the year. Not a target load, but one that made me a confident hunter.
I don't know if Varget is going to be happy down around 1800 fps, but it might still be ok with that heavy bullet. There is a trade off between velocity in the "easy" zone and using a powder which gives a soft launch but starts to show erratic ignition consistencies at the lower pressure levels. The old "28.5 grains of 4895 and a 3/4 grain tuft of fluffed-up Dacron" load might be a lot better, or an off-book load of Reloder 7. I can offer you a simple assignment with that 311299 that someone once gave me, and I highly recommend it. Get yourself a pound of Alliant Unique. Start in at about 11 grains and start working up in .2-grain increments, ten shots per group repeated at least once per charge on different days, until you go through two full vibration node cycles and end up at about 15-1600 fps. Somewhere in there you should find at least one node that bugholes, likely two. Keep your targets and study the pattern development well as you work up to a node, blow through it, and come back around to it again. What you observe and learn will help you work up cast bullet loads for fixed ammunition for the rest of your life. If your basic loading techniques are squared away, you'll get fhat bullet to group very well, and have a load that carries to 300 yards with pinpoint accuracy. As a bonus it will give you a built-in wind-doping challenge too, one that mimics much further shooting distances.
The Barlow bullet design can be pushed a little and can turn in some very impressive groups at reasonable velocities (examine CBA records for evidence), but it has its limits as you start to push past middleweight load levels. Fiver has done quite well at high velocity with a two-diameter bullet, but he fit the entire bullet to the entire throat like a glove and had a two-diameter throat to start with, then tinkered with alloy, lube, powder, and primers until he found a fine point in the balance of everything that worked. Lots of work there and it only will work in certain rifles, and almost no one succeeds in this.
The big paradigm and roadblock has been that not very many people understood what WOULD deliver respectable groups out of an average "deer rifle" or milsurp at velocities approaching those of normal jacketed bullet loads, even if they know the limitations of the usual approach to bullet fit, alloy selection, and loading techniques.. Over time, a small group of people started chipping away at the high velocity challenge and figured out several ways to go about it. There are many disagreements, some animosity, some divergence of methods (some include 30" barrels and heavy benchrest stocks with super-slow twist barrels), but lots of ways to get there. One of the easiest that works with factory rifles of normal weight, production barrels, and standard rates of twist and the usual .308 Winchester throat, you are using now. Not much to it, just cast a good quality bullets, of about the right alloy, sized to fit the freebore diameter of the throat, use the same powder you would for jacketed, adjust your neck tension for cast bullets, and apply the usual long-range accuracy techniques to your loading and BAM! Instant success. CAVEAT EMPTOR: Try that same bullet and powder and jam and alloy combination in a .30-'06 and you may have VERY different results because the throat, and thus dynamic fit, are going to be different and you will need to adjust.
You could screw a tight-necked .308 match-chambered, one turn in 17" ROT heavy varmint Bartlein barrel on there with a 36-power target scope on top and probably do 2-3 MOA out to the transonic point at 2500 fps MV with your 311299, but if you can do better with the equipment you already have now.....why fool with the expense and weight?
You can also paper-patch .302" castings with two wraps of wet Vellum and a twist, and push them past maximum jacketed speeds with fine accuracy. Or you can use a self-aligning bullet of milder alloy, powder coat it and allow the alloy hardness to normalize for a week or two, give it some room to wiggle, push it with a medium-burning rifle powder, and go full speed. But again, you have something going right off the bat that others have already proven viable at long distance, so there ya go.
On jamming the bullet. That is part of the static fit equation. Seating depth, like with jax, is a tool which affects shot initiation pressure pressure/powder burn rate/pressure rise and if there is any freedom, it affects dynamic launch alignment. Some bullet/throat/alloy/powder systems need to be crammed in tight statically so the bullet is FORCED straight and some align even better than you can force them if you set up the system so the bullet finds the centerline of the bore on its own. Totally different things requiring different bullet shapes/throat shapes, powder selection, and alloy makeup. If you're jumping the bullet, it may need more tin to be just a tad tougher. If jamming, you want it to engrave easily but be supported everywhere possible so it doesn't smoosh around and get distorted before gets fully engraved. It isn't true that "some rifles like jam", it is true that some bullet, alloy, and load combinations do with certain guns that have certain throat shapes. It would be more true to say that a rifle with squared receiver and lapped bolt lugs are more consistent shooters without jam than those that need some pressure to take up the slack in the breech-locking system. Also, jamming the shoulder/datum point at less than zero headspace (NEVER a good idea, IMO) is way different than creating a tiny bit of headspace but jamming the case head back against the breech face and compressing the ejector spring with just the pressure of the bullet against the throat/land origin, so we need to be specific here.
Those 311299s shot just ok for me out of my '06 at 1950 fps using a dirty, slow load of H4350. For some reason (probably the nose being fatter) the Lee 312-185 at the same speed did better and had no flyers. That was my go-to deer whacker for quite a few years, 1.5 moa for ten shots from field positions in any weather, any temperature I encountered, on any given day of the year. Not a target load, but one that made me a confident hunter.
I don't know if Varget is going to be happy down around 1800 fps, but it might still be ok with that heavy bullet. There is a trade off between velocity in the "easy" zone and using a powder which gives a soft launch but starts to show erratic ignition consistencies at the lower pressure levels. The old "28.5 grains of 4895 and a 3/4 grain tuft of fluffed-up Dacron" load might be a lot better, or an off-book load of Reloder 7. I can offer you a simple assignment with that 311299 that someone once gave me, and I highly recommend it. Get yourself a pound of Alliant Unique. Start in at about 11 grains and start working up in .2-grain increments, ten shots per group repeated at least once per charge on different days, until you go through two full vibration node cycles and end up at about 15-1600 fps. Somewhere in there you should find at least one node that bugholes, likely two. Keep your targets and study the pattern development well as you work up to a node, blow through it, and come back around to it again. What you observe and learn will help you work up cast bullet loads for fixed ammunition for the rest of your life. If your basic loading techniques are squared away, you'll get fhat bullet to group very well, and have a load that carries to 300 yards with pinpoint accuracy. As a bonus it will give you a built-in wind-doping challenge too, one that mimics much further shooting distances.
The Barlow bullet design can be pushed a little and can turn in some very impressive groups at reasonable velocities (examine CBA records for evidence), but it has its limits as you start to push past middleweight load levels. Fiver has done quite well at high velocity with a two-diameter bullet, but he fit the entire bullet to the entire throat like a glove and had a two-diameter throat to start with, then tinkered with alloy, lube, powder, and primers until he found a fine point in the balance of everything that worked. Lots of work there and it only will work in certain rifles, and almost no one succeeds in this.
The big paradigm and roadblock has been that not very many people understood what WOULD deliver respectable groups out of an average "deer rifle" or milsurp at velocities approaching those of normal jacketed bullet loads, even if they know the limitations of the usual approach to bullet fit, alloy selection, and loading techniques.. Over time, a small group of people started chipping away at the high velocity challenge and figured out several ways to go about it. There are many disagreements, some animosity, some divergence of methods (some include 30" barrels and heavy benchrest stocks with super-slow twist barrels), but lots of ways to get there. One of the easiest that works with factory rifles of normal weight, production barrels, and standard rates of twist and the usual .308 Winchester throat, you are using now. Not much to it, just cast a good quality bullets, of about the right alloy, sized to fit the freebore diameter of the throat, use the same powder you would for jacketed, adjust your neck tension for cast bullets, and apply the usual long-range accuracy techniques to your loading and BAM! Instant success. CAVEAT EMPTOR: Try that same bullet and powder and jam and alloy combination in a .30-'06 and you may have VERY different results because the throat, and thus dynamic fit, are going to be different and you will need to adjust.
You could screw a tight-necked .308 match-chambered, one turn in 17" ROT heavy varmint Bartlein barrel on there with a 36-power target scope on top and probably do 2-3 MOA out to the transonic point at 2500 fps MV with your 311299, but if you can do better with the equipment you already have now.....why fool with the expense and weight?
You can also paper-patch .302" castings with two wraps of wet Vellum and a twist, and push them past maximum jacketed speeds with fine accuracy. Or you can use a self-aligning bullet of milder alloy, powder coat it and allow the alloy hardness to normalize for a week or two, give it some room to wiggle, push it with a medium-burning rifle powder, and go full speed. But again, you have something going right off the bat that others have already proven viable at long distance, so there ya go.
On jamming the bullet. That is part of the static fit equation. Seating depth, like with jax, is a tool which affects shot initiation pressure pressure/powder burn rate/pressure rise and if there is any freedom, it affects dynamic launch alignment. Some bullet/throat/alloy/powder systems need to be crammed in tight statically so the bullet is FORCED straight and some align even better than you can force them if you set up the system so the bullet finds the centerline of the bore on its own. Totally different things requiring different bullet shapes/throat shapes, powder selection, and alloy makeup. If you're jumping the bullet, it may need more tin to be just a tad tougher. If jamming, you want it to engrave easily but be supported everywhere possible so it doesn't smoosh around and get distorted before gets fully engraved. It isn't true that "some rifles like jam", it is true that some bullet, alloy, and load combinations do with certain guns that have certain throat shapes. It would be more true to say that a rifle with squared receiver and lapped bolt lugs are more consistent shooters without jam than those that need some pressure to take up the slack in the breech-locking system. Also, jamming the shoulder/datum point at less than zero headspace (NEVER a good idea, IMO) is way different than creating a tiny bit of headspace but jamming the case head back against the breech face and compressing the ejector spring with just the pressure of the bullet against the throat/land origin, so we need to be specific here.
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Idaholewis
Active Member
Idaholewis
Active Member
fiver
Well-Known Member
i'll explain why the jam fit does and doesn't work.
1. the bolt then becomes a reloading press.
2. where the bullet makes contact and how the bullet is seated that final stage becomes more important.
3. the type of bolt face you have becomes more important in influencing how you operate the press.
1. the bolt then becomes a reloading press.
2. where the bullet makes contact and how the bullet is seated that final stage becomes more important.
3. the type of bolt face you have becomes more important in influencing how you operate the press.
Ian
Notorious member
Ohhhhh, but there's so much more to it. Remember my bullet design for the XCB? The one Brad and I both got back when the project first took off? Remember me going on about doping out the "Morse taper fit" design? Remember why it was a failure?
This is for Lewis, I'll try to explain static and dynamic fit as I understand it here, as a sort of rough draft for a future, illustrated article. I explain by example and you have to use your imagination to form a picture of my descriptions.
If you do make a positive, matching, taper fit design, have less than a thousandth of total loaded neck clearance to the chamber neck, and the jam the bullet hard against the ball seat to force perfect alignment, then three things happen, all of of them bad, one resulting from the other: First, the engraving pressure is extremely high, so the powder pressure builds very quickly and to a very high pressure before the bullet even begins to move. This is like an air compressor without an unloader valve having to start from a standstill against full head pressure, or a locomotive trying to start a train of cars all at once without having any slack in the couplings, IOW VERY high load to overcome static inertia and forward resistance. Second, that very high load is applied where? The base of the bullet, right? By what means? Gas pressure, right? So if the pressure to move that bullet is quite high, the neck is going to obturate the chamber before the bullet gets a chance to move and gas pressure rushes around the gas check and flame-cuts the hell out of the back two driving bands of the bullet. Then, as the bullet starts to move, the base gets wadded up like a soda straw wrapper. None of that translates to sub-moa groups. Third, any metal smooshed up by the pressure behind bulges the base and then gets raked off and swaged into the only place it has to go, which is the little space in between the case mouth and end of the chamber neck. I've pulled a lot of lead rings out of there with a bronze brush when working with jammed, morse-taper bullets that weren't made hard as coffin nails, i.e. straight linotype. Anything soft or even sorta kinda fast powder, without a buffer in front of it, made hash instead of groups for me. A good example of this sort of fit would be the NOE XCB bullet and a freshly cut, SAAMI-spec .30-'06 chamber. To make it work you need a slow powder and not too tough of an alloy, but tough enough. Lots of tin to stiffen the bullet in all directions but improve flow. Another option is water-dropped 60/40 wheelweights and soft scrap lead, this should be around 2% antimony and less than 1/4% tin. Heat treated to 19 bhn this alloy will draw well, engrave well, but also be stiff and resist gross bending forces at launch. Hard, brittle alloys are a NO GO with a jammed, fully-matching fit. The CBA crowd almost all do it this way but they use a very gradual taper and the manage to get away with it.....within the inherent velocity limitations of Linotype alloy (more on that later).
Now, consider some other fitment options. The .308 throat and the NOE version of the XCB with tapered nose meant to perfectly match a 1.5° per side throat of the .30 XCB wildcat chamber or any standard .30-'06 throat. The .308 throat has a .310-.311" parallel freebore for at least .100" and an abrupt taper to the tops of the lands, making it in effect a three-diameter system if you count the case neck. Neck diameter, abrupt taper to freebore at the entrance, abrupt taper to the bore diameter, with groove diameter falling in between freebore diameter and bore diameter. Step, step, step. Not a good matching fit we would think. Got it? Ok, now you take a bullet like the XCB whose body is sized to fit that freebore, or middle step, and the nose is tapered so it can't really fit more than one point in the throat (which will be the front edge of the ball seat where it intersects the tops of the lands, assuming you jam it in that far), and has no excess nose hanging out front dependent on the tops of the narrow lands for support. Got that? Only a tiny bit of the bullet is supported by freebore, the rest is supported by the case neck in the chamber, and that neck support is going to go away at a certain pressure level. That pressure level has to be less than engraving pressure. The ONLY reasons this works is due to the throat mismatch and the bullet being engraved gradually and not all at once, and as the dynamic change is happening to the bullet, remaining straight in line with the bore as it is drawn through the throat actually IS the path of least resistance. The force to move the bullet from rest is slow, the increase in resistance is gradual, and the pressure doesn't peak to bullet-damaging levels until the bullet is safely moved straight into the throat (assuming you used a suitable powder burn speed to make that happen). Make sense? This scenario working out well is also dependent on a bullet alloy which is malleable enough to deform without too much resistance, but still tough enough to guide itself straight with very little support. It's a balance. Change one thing out of the functional range and it goes to hell. Make the alloy too soft and it rivets in the case neck even though the engraving pressure is low. Use too fast of a powder and even a tough bullet rivets and gets washed out base bands before it is able to transition to the safety of the throat. Screw up your static alignment with an off-center case neck and it has no chance.
Take that same .308 bullet launcher and try to match the hatch to those three steps with abrupt transitions. It works if you don't depend on the nose for alignment or have too much nose out front. Your launch pressure will be extremely high if jammed because the bullet has to deform in several places all at once before it can move. If you use a tough alloy and don't have much bullet in the case neck, it can work pretty well, maybe, but things have to be PERFECT.
Now, let's look at the reverse fitment scenario, which doesn't work for beans above about 1800 fps but is pretty much THE world standard and why almost everyone fails at high velocity: A throat with a straight taper, or one which has worn from use into the typical parabolic trumpet-bell shape, and poke a bullet shaped like two, different diameter cylinders into it. The nose cylinder is sized for a slight interference fit for best results (ask anyone), the back half of the nose in front of the front driving band supported only by air, the front edge of the front band is supported at only one point somewhere in that throat taper where the sizes match, and the majority of the bullet body is supported only by the case neck which most of the time is so crooked or off-center in the chamber due to standard, jax loading dies that the bullet has no hope of alignment. SO in review, you have the tops of the lands supporting half the nose (figure that surface area out, it's infinitismal), one ring of contact with the front edge of the front band (also infinitismal and theoretically zero, even if the band is jammed into the throat taper) and the case neck supporting the rest. Basically you have a static fit supported only by hopes and dreams, and the thing that's doing 99% of the support work (the case neck) is a house of cards. Light the primer and the bullet goes any way but straight as it moves into the bore, it gets mangled, engaved more on one side than the other, and comes out the muzzle wobbling like me throwing a football. That wobbling causes massive group dispersion, and the faster you go the worse it is because the bullet damage gets worse as launch pressure necessary for higher velocity is increased, and the external ballistics play more and more on those imbalances the faster the bullet spins. This is what was happening to those 311299s at 2300+ fps. If you recover some from that snow bank in the spring, you'll see the effects of what I'm talking about.
Now, let's talk about yet another scenario: How to choose a bullet to fit a typical, worn throat shape or either of the above conical or stepped throats. If the bullet has a concave nose, nothing parallel except the driving bands, plenty of displacement area for lead to move so that launch pressure is low and the bullet base doesn't see damaging forces until sealed up and safely engraved straight in the barrel, then the exact points of fit and support will come naturally to the bullet both statically and dynamically. The key to making it work is a weak alloy but heat treated or powder coated for toughness and abrasion resistance. These bullets can be loaded with medium to slow rifle powder and jumped a considerable distance and still shoot well. That means ammunition can be made to fit a variety of rifles with subtle differences and interchange with acceptable accuracy. That means that the ammunition will function in a dirty rifle or cold rifle or if the bullets grow a little over time they will still fit and function. Not a picky thing. Also, the ammunition can work in an autoloader with weak camming action because you don't have to jam the bullet. Even a suppressed autoloader that cakes up the chamber with filth and grime. You don't have to fit your cases to the chamber as tightly as with the other fitment methods because the bullet can self-align (to a point) and the STATIC fit of the cartridge in the chamber isn't nearly as critical. This is a highly dynamic system, very versatile, and very accurate if done correctly. The drawback? Yes, there is one. There are VERY few moulds of this self-aligning design. The best ones are offered by MP Molds, designed by Bob Kell (45 2.1). The .22 NATO, 311-180 Silhouette, and 359-220 are perfect examples of this design. If you want drawings of similar concepts (Bob won't release a drawing to the public), look at Accurate Mold's catalog for the 31-188G and 31-157G.
A word on the velocity limitations of linotype and other hard, brittle alloys. Unless you give them a jacket (paint, paper, copper), they begin to fail at high velocity because of land stresses on the sides of the engraves. The alloy crushes on a microscopic level under stress and falls apart. The engraves get washed out a little and the gas jetting up the engraves when the bullet exits the muzzle crown throws the shot, and then the next, and so on but rarely in the same place. Your bullets to not have to be rock-hard and brittle to shoot well at HV, quite the opposite in fact. Again, alloy has to be balanced to the system like everything else does because the whole system has to work together to work at all. Change one thing, you'll likely need to change something else to restore the balance. Some systems of dynamic fit require different powders, neck tension, jump, primers than others, possibly a buffer, probably a very specific alloy, and so on. Some alloys handle fast rifling twist rates better than others. Some bullet designs prefer wide lands, some don't care. You likely won't have good results if you just grab a bullet that looks good and stuff it in any old rifle without regard to dynamic fit or how to set things up to optimize those dynamics for a balanced, undamaged, straight-shooting bullet to emerge from the muzzle.
Fit. Alloy. Powder. The big three factors for high-velocity cast bullet accuracy. Understand how to choose wisely for your desired application and you will have success.
This is for Lewis, I'll try to explain static and dynamic fit as I understand it here, as a sort of rough draft for a future, illustrated article. I explain by example and you have to use your imagination to form a picture of my descriptions.
If you do make a positive, matching, taper fit design, have less than a thousandth of total loaded neck clearance to the chamber neck, and the jam the bullet hard against the ball seat to force perfect alignment, then three things happen, all of of them bad, one resulting from the other: First, the engraving pressure is extremely high, so the powder pressure builds very quickly and to a very high pressure before the bullet even begins to move. This is like an air compressor without an unloader valve having to start from a standstill against full head pressure, or a locomotive trying to start a train of cars all at once without having any slack in the couplings, IOW VERY high load to overcome static inertia and forward resistance. Second, that very high load is applied where? The base of the bullet, right? By what means? Gas pressure, right? So if the pressure to move that bullet is quite high, the neck is going to obturate the chamber before the bullet gets a chance to move and gas pressure rushes around the gas check and flame-cuts the hell out of the back two driving bands of the bullet. Then, as the bullet starts to move, the base gets wadded up like a soda straw wrapper. None of that translates to sub-moa groups. Third, any metal smooshed up by the pressure behind bulges the base and then gets raked off and swaged into the only place it has to go, which is the little space in between the case mouth and end of the chamber neck. I've pulled a lot of lead rings out of there with a bronze brush when working with jammed, morse-taper bullets that weren't made hard as coffin nails, i.e. straight linotype. Anything soft or even sorta kinda fast powder, without a buffer in front of it, made hash instead of groups for me. A good example of this sort of fit would be the NOE XCB bullet and a freshly cut, SAAMI-spec .30-'06 chamber. To make it work you need a slow powder and not too tough of an alloy, but tough enough. Lots of tin to stiffen the bullet in all directions but improve flow. Another option is water-dropped 60/40 wheelweights and soft scrap lead, this should be around 2% antimony and less than 1/4% tin. Heat treated to 19 bhn this alloy will draw well, engrave well, but also be stiff and resist gross bending forces at launch. Hard, brittle alloys are a NO GO with a jammed, fully-matching fit. The CBA crowd almost all do it this way but they use a very gradual taper and the manage to get away with it.....within the inherent velocity limitations of Linotype alloy (more on that later).
Now, consider some other fitment options. The .308 throat and the NOE version of the XCB with tapered nose meant to perfectly match a 1.5° per side throat of the .30 XCB wildcat chamber or any standard .30-'06 throat. The .308 throat has a .310-.311" parallel freebore for at least .100" and an abrupt taper to the tops of the lands, making it in effect a three-diameter system if you count the case neck. Neck diameter, abrupt taper to freebore at the entrance, abrupt taper to the bore diameter, with groove diameter falling in between freebore diameter and bore diameter. Step, step, step. Not a good matching fit we would think. Got it? Ok, now you take a bullet like the XCB whose body is sized to fit that freebore, or middle step, and the nose is tapered so it can't really fit more than one point in the throat (which will be the front edge of the ball seat where it intersects the tops of the lands, assuming you jam it in that far), and has no excess nose hanging out front dependent on the tops of the narrow lands for support. Got that? Only a tiny bit of the bullet is supported by freebore, the rest is supported by the case neck in the chamber, and that neck support is going to go away at a certain pressure level. That pressure level has to be less than engraving pressure. The ONLY reasons this works is due to the throat mismatch and the bullet being engraved gradually and not all at once, and as the dynamic change is happening to the bullet, remaining straight in line with the bore as it is drawn through the throat actually IS the path of least resistance. The force to move the bullet from rest is slow, the increase in resistance is gradual, and the pressure doesn't peak to bullet-damaging levels until the bullet is safely moved straight into the throat (assuming you used a suitable powder burn speed to make that happen). Make sense? This scenario working out well is also dependent on a bullet alloy which is malleable enough to deform without too much resistance, but still tough enough to guide itself straight with very little support. It's a balance. Change one thing out of the functional range and it goes to hell. Make the alloy too soft and it rivets in the case neck even though the engraving pressure is low. Use too fast of a powder and even a tough bullet rivets and gets washed out base bands before it is able to transition to the safety of the throat. Screw up your static alignment with an off-center case neck and it has no chance.
Take that same .308 bullet launcher and try to match the hatch to those three steps with abrupt transitions. It works if you don't depend on the nose for alignment or have too much nose out front. Your launch pressure will be extremely high if jammed because the bullet has to deform in several places all at once before it can move. If you use a tough alloy and don't have much bullet in the case neck, it can work pretty well, maybe, but things have to be PERFECT.
Now, let's look at the reverse fitment scenario, which doesn't work for beans above about 1800 fps but is pretty much THE world standard and why almost everyone fails at high velocity: A throat with a straight taper, or one which has worn from use into the typical parabolic trumpet-bell shape, and poke a bullet shaped like two, different diameter cylinders into it. The nose cylinder is sized for a slight interference fit for best results (ask anyone), the back half of the nose in front of the front driving band supported only by air, the front edge of the front band is supported at only one point somewhere in that throat taper where the sizes match, and the majority of the bullet body is supported only by the case neck which most of the time is so crooked or off-center in the chamber due to standard, jax loading dies that the bullet has no hope of alignment. SO in review, you have the tops of the lands supporting half the nose (figure that surface area out, it's infinitismal), one ring of contact with the front edge of the front band (also infinitismal and theoretically zero, even if the band is jammed into the throat taper) and the case neck supporting the rest. Basically you have a static fit supported only by hopes and dreams, and the thing that's doing 99% of the support work (the case neck) is a house of cards. Light the primer and the bullet goes any way but straight as it moves into the bore, it gets mangled, engaved more on one side than the other, and comes out the muzzle wobbling like me throwing a football. That wobbling causes massive group dispersion, and the faster you go the worse it is because the bullet damage gets worse as launch pressure necessary for higher velocity is increased, and the external ballistics play more and more on those imbalances the faster the bullet spins. This is what was happening to those 311299s at 2300+ fps. If you recover some from that snow bank in the spring, you'll see the effects of what I'm talking about.
Now, let's talk about yet another scenario: How to choose a bullet to fit a typical, worn throat shape or either of the above conical or stepped throats. If the bullet has a concave nose, nothing parallel except the driving bands, plenty of displacement area for lead to move so that launch pressure is low and the bullet base doesn't see damaging forces until sealed up and safely engraved straight in the barrel, then the exact points of fit and support will come naturally to the bullet both statically and dynamically. The key to making it work is a weak alloy but heat treated or powder coated for toughness and abrasion resistance. These bullets can be loaded with medium to slow rifle powder and jumped a considerable distance and still shoot well. That means ammunition can be made to fit a variety of rifles with subtle differences and interchange with acceptable accuracy. That means that the ammunition will function in a dirty rifle or cold rifle or if the bullets grow a little over time they will still fit and function. Not a picky thing. Also, the ammunition can work in an autoloader with weak camming action because you don't have to jam the bullet. Even a suppressed autoloader that cakes up the chamber with filth and grime. You don't have to fit your cases to the chamber as tightly as with the other fitment methods because the bullet can self-align (to a point) and the STATIC fit of the cartridge in the chamber isn't nearly as critical. This is a highly dynamic system, very versatile, and very accurate if done correctly. The drawback? Yes, there is one. There are VERY few moulds of this self-aligning design. The best ones are offered by MP Molds, designed by Bob Kell (45 2.1). The .22 NATO, 311-180 Silhouette, and 359-220 are perfect examples of this design. If you want drawings of similar concepts (Bob won't release a drawing to the public), look at Accurate Mold's catalog for the 31-188G and 31-157G.
A word on the velocity limitations of linotype and other hard, brittle alloys. Unless you give them a jacket (paint, paper, copper), they begin to fail at high velocity because of land stresses on the sides of the engraves. The alloy crushes on a microscopic level under stress and falls apart. The engraves get washed out a little and the gas jetting up the engraves when the bullet exits the muzzle crown throws the shot, and then the next, and so on but rarely in the same place. Your bullets to not have to be rock-hard and brittle to shoot well at HV, quite the opposite in fact. Again, alloy has to be balanced to the system like everything else does because the whole system has to work together to work at all. Change one thing, you'll likely need to change something else to restore the balance. Some systems of dynamic fit require different powders, neck tension, jump, primers than others, possibly a buffer, probably a very specific alloy, and so on. Some alloys handle fast rifling twist rates better than others. Some bullet designs prefer wide lands, some don't care. You likely won't have good results if you just grab a bullet that looks good and stuff it in any old rifle without regard to dynamic fit or how to set things up to optimize those dynamics for a balanced, undamaged, straight-shooting bullet to emerge from the muzzle.
Fit. Alloy. Powder. The big three factors for high-velocity cast bullet accuracy. Understand how to choose wisely for your desired application and you will have success.
Last edited:
Bret4207
At the casting bench in the sky. RIP Bret.
Gonna have to come back and re-read this. Might be a "Sticky" in the making!!!!
Yeah, I was a "Golden Boolit"Recipient too. Boy, does that ever make a difference when you let people know about that on a loan application! Well, okay, not so much...........
Yeah, I was a "Golden Boolit"Recipient too. Boy, does that ever make a difference when you let people know about that on a loan application! Well, okay, not so much...........
