Ian
Notorious member
Not at this point. I'm not accustomed to it mattering much until trying to get below 3/4 MOA, you think I should?
My quest for speed and accuracy with powder-coated cast bullets
- Thread starter Ian
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Not at this point. I'm not accustomed to it mattering much until trying to get below 3/4 MOA, you think I should?
Ian
Notorious member
I just weighed the last ten 22 MX3 bullets, in order:
68.4
68.4
68.4
68.3
68.5
68.4
68.4
68.4
68.4
68.4
Did more modeling. The only powder that comes close to peaking as far down the barrel as 3031 is 4831, and it still peaks a bit sooner (1.78 vs 2.02 at 2550 fps respective loadings. 100% fill for 4831 and 90% for 3031 to get the same speed). That got me thinking about the fouling I was getting in the first two inches of the barrel....I wonder if the initial pressure is too LOW and peaking too late, causing some PC to wash out? I've tried capturing these bullets in my oiled sawdust trap for examination but they completely disintegrate, shedding pieces all the way in to three feet where the gas check (turned inside out) stops.
I'm going to shoot the last ten with 19.0 grains of my old high-nitro friend Reloder 7, keeping everything else the same. That should keep pressure peak the same as 3031 and only give up about 75 fps. Looking at about 2625 tp 2650 with this one while moving the pressure peak back half an inch closer to the chamber.
68.4
68.4
68.4
68.3
68.5
68.4
68.4
68.4
68.4
68.4
Did more modeling. The only powder that comes close to peaking as far down the barrel as 3031 is 4831, and it still peaks a bit sooner (1.78 vs 2.02 at 2550 fps respective loadings. 100% fill for 4831 and 90% for 3031 to get the same speed). That got me thinking about the fouling I was getting in the first two inches of the barrel....I wonder if the initial pressure is too LOW and peaking too late, causing some PC to wash out? I've tried capturing these bullets in my oiled sawdust trap for examination but they completely disintegrate, shedding pieces all the way in to three feet where the gas check (turned inside out) stops.
I'm going to shoot the last ten with 19.0 grains of my old high-nitro friend Reloder 7, keeping everything else the same. That should keep pressure peak the same as 3031 and only give up about 75 fps. Looking at about 2625 tp 2650 with this one while moving the pressure peak back half an inch closer to the chamber.
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Ian
Notorious member
Fair enough. I weighed some Lee 55 grainers last night and had an extreme spread of over a grain. Yuck. Found 20 that all weighed and measured about the same and got them ready to load.
I made five MX3/RX7 loads with Dacron filler and five without. The load is an 80% fill and I didn't like the way powder grains would slide up between the bullet body and the case shoulder whrn the case is horizontal; it worries me that powder beside the bullet might force it crooked somehow. Five shots won't tell much but its what I got for the next 2-3 weeks whole I wait for more to age.
I'm looking to load the Lee 55s with 4320 because it looks like it will burn ok with the lighter bullet, not be too spikey, and will keep velocities reasonable (under 2800fps) at high densities. 95% case full models 2700 fps at 29kpsi with peak at 1.5" bullet travel and a relatively slow pressure rise. Being a single-base powder, ignitoon shouldn't be a problem. The other reason for trying 4320 is I have eight pounds if it that doesn't work very well in anything else I shoot.
Looks like soaking rain will continue for another day or so, and start again next weekend, so who know when I'll get to shoot again.
I made five MX3/RX7 loads with Dacron filler and five without. The load is an 80% fill and I didn't like the way powder grains would slide up between the bullet body and the case shoulder whrn the case is horizontal; it worries me that powder beside the bullet might force it crooked somehow. Five shots won't tell much but its what I got for the next 2-3 weeks whole I wait for more to age.
I'm looking to load the Lee 55s with 4320 because it looks like it will burn ok with the lighter bullet, not be too spikey, and will keep velocities reasonable (under 2800fps) at high densities. 95% case full models 2700 fps at 29kpsi with peak at 1.5" bullet travel and a relatively slow pressure rise. Being a single-base powder, ignitoon shouldn't be a problem. The other reason for trying 4320 is I have eight pounds if it that doesn't work very well in anything else I shoot.
Looks like soaking rain will continue for another day or so, and start again next weekend, so who know when I'll get to shoot again.
Hawk
Well-Known Member
Not to Sidetrack you thread, or distract from what you're doing, just wondering why you decided on the MX3 mold with the Sharp shoulder as opposed to a more rounded ogive with a flat point.
Most of my experience with bullet casting has been for pistols and revolvers, so I'm just trying to learn a little more about rifle. Especially interested in the 223 and I own a couple of ARs.
Most of my experience with bullet casting has been for pistols and revolvers, so I'm just trying to learn a little more about rifle. Especially interested in the 223 and I own a couple of ARs.
Ian
Notorious member
The nose had nothing to do with my chouce. I picked that bullet based on the drawing and the dimensions of my MVP's throat, looking to filk space and length essentially. Unfortunately, the mould actually cast .004" larger on the front bearing band (nose base) than the drawing so I had to seat it about .100" deeper than I planned. It still works ok but engraves the nose band too much and has a lot of jump before band 2 and 3 contact the throat.
Ian
Notorious member
The drizzle broke for just long enough to get some shooting done.
First was the 19.0/rx7/mx3 loads. Five rounds into 1-5/8", 2,676 average, 37.1 SD. Shot poi to velocity numbers indicate no correlation, for exampe 3 and 4 had the highest velocity spread and identical elevation, while 2 printed high and was 37 fps faster than 1. 1 printed lowest but was only 6 fps off of the average. This is pretty typical for unlubed pc.
Next five was same but with Dacron. First shot (6) overlapped the first shot from the first group, then the shots started going wild. 4th missed the entire 31x10.5" tire, last one went just off the upper left corner of the target paper. Sum ting wong. 2,757 average and 9.8 SD, so the Dacron helped the burn, anyway
So then I went after the powder coated Lee bullets, gas-checked after the fact. First shot missed the tire again so I backed off to 75 yards and tried again. 9 into 3-1/8", woo-hoo. Velocity was predicted to be 2,698 but all I got was 2,471 with an SD of 59.6. I have no idea why they didn't shoot, or why the fps was off by well over 200 fps.
First was the 19.0/rx7/mx3 loads. Five rounds into 1-5/8", 2,676 average, 37.1 SD. Shot poi to velocity numbers indicate no correlation, for exampe 3 and 4 had the highest velocity spread and identical elevation, while 2 printed high and was 37 fps faster than 1. 1 printed lowest but was only 6 fps off of the average. This is pretty typical for unlubed pc.
Next five was same but with Dacron. First shot (6) overlapped the first shot from the first group, then the shots started going wild. 4th missed the entire 31x10.5" tire, last one went just off the upper left corner of the target paper. Sum ting wong. 2,757 average and 9.8 SD, so the Dacron helped the burn, anyway
So then I went after the powder coated Lee bullets, gas-checked after the fact. First shot missed the tire again so I backed off to 75 yards and tried again. 9 into 3-1/8", woo-hoo. Velocity was predicted to be 2,698 but all I got was 2,471 with an SD of 59.6. I have no idea why they didn't shoot, or why the fps was off by well over 200 fps.
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Ian
Notorious member
Got another batch of MX3 bullets going, this time trying for 20-24 bhn. The PBTP poly tgic powder took the overtemp and overbake well as far as I can tell.
When these stabilize I'll resume testing by going back to 21.6 grains of 3031 and compare to previous velocities and group dispersion. Then possibly have another go with Reloder 7 (sans Dacron this time!) and maybe try a slower powder as well.
If the harder bullets don't seem to make a difference to the flyers early on, I'm going to try a few more tweaks.
Post sizing. I have been shooting the MX3s as-coated up to now, not having a sizer that will make them .226" I have blank sizers and may finish one out to just clean these up at .226" or so.
Sanding the coating off of the base gas checks. I'm really starting to wonder if the uneven coating thickness on the bases from standing up on foil is causing my flyers. I dug through and found a really bad one:
When these stabilize I'll resume testing by going back to 21.6 grains of 3031 and compare to previous velocities and group dispersion. Then possibly have another go with Reloder 7 (sans Dacron this time!) and maybe try a slower powder as well.
If the harder bullets don't seem to make a difference to the flyers early on, I'm going to try a few more tweaks.
Post sizing. I have been shooting the MX3s as-coated up to now, not having a sizer that will make them .226" I have blank sizers and may finish one out to just clean these up at .226" or so.
Sanding the coating off of the base gas checks. I'm really starting to wonder if the uneven coating thickness on the bases from standing up on foil is causing my flyers. I dug through and found a really bad one:
RicinYakima
High Steppes of Eastern Washington
"Sanding the coating off of the base gas checks. I'm really starting to wonder if the uneven coating thickness on the bases from standing up on foil is causing my flyers. I dug through and found a really bad one:"
I would consider that as an issue to work on, as we know that the gas pressure works at 90* to the surface. So varing surface on the base would make unequal pressures at some point. At least I think so.
I would consider that as an issue to work on, as we know that the gas pressure works at 90* to the surface. So varing surface on the base would make unequal pressures at some point. At least I think so.
Ian
Notorious member
Mmm hhm. The bullet not only has to pass the crown, but three muzzle brake chambers and a long stack of clipped suppressor baffles.
I feel kinda stupid not thinking about this before when loading for the .5.56 but most of my other pc work has been with bevel-base bullets or gas-check designs without the check and the base quality doesn't matter so much as long as the edge that breaks the seal at the crown is clean, square, and true. One thing that does affect accuracy is plain-base designs that have a sharp edge and powder-coat flashing on them, or dents in the edge from the shakenbake process. I avoid sharp-base designs for just that reason.
Most of the time I try to only fix problems that matter, and now that I've done a good bit of shooting with this bullet using a minimal-effort approach, it's time to start figuring out what they are and aren't.
I feel kinda stupid not thinking about this before when loading for the .5.56 but most of my other pc work has been with bevel-base bullets or gas-check designs without the check and the base quality doesn't matter so much as long as the edge that breaks the seal at the crown is clean, square, and true. One thing that does affect accuracy is plain-base designs that have a sharp edge and powder-coat flashing on them, or dents in the edge from the shakenbake process. I avoid sharp-base designs for just that reason.
Most of the time I try to only fix problems that matter, and now that I've done a good bit of shooting with this bullet using a minimal-effort approach, it's time to start figuring out what they are and aren't.
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fiver
Well-Known Member
I'm flummoxed about the 'great' group and then things going to hell.
the only time I have seen that was with the 61 series of soap lubes with the GOO.
it was absolutely the tightest grouping lube I ever seen,,,, for 5-6 shots, then bam berm, berm, berm, thanks for comin, see ya tomorrow.
the only time I have seen that was with the 61 series of soap lubes with the GOO.
it was absolutely the tightest grouping lube I ever seen,,,, for 5-6 shots, then bam berm, berm, berm, thanks for comin, see ya tomorrow.
Ian
Notorious member
Evidently the Dacron tore the hell out of the bullet bases that were poking down into the powder space, or something. When the third shot went nearly off the paper I pulled the bolt and suppressor to check the bore and then examined the suppressor and brake for baffle strikes, gas check fragments, copper wash, or anything else unusual, but it all looked fine and passed the salt-shaker test. The fired cases looked normal, too.
I cleaned the bore with brush and solvent after all the shooting and it didn't appear that there was much fouling other than a lot of carbon that took two brushings and about a dozen patches to get out.
I cleaned the bore with brush and solvent after all the shooting and it didn't appear that there was much fouling other than a lot of carbon that took two brushings and about a dozen patches to get out.
Hawk
Well-Known Member
I know the PC coating in pretty hard, but do you think it's hard enough that the pressure from the powder wouldn't flatten it out on the base of the bullet in short order.
I gas check when resizing after coating and don't have a lot of experience with rifle PC coated bullets, so I'm just tap dancing here.
It seems that the pressure from the powder burn would iron out the PC on the base of the GC, at least until exiting the barrel . Maybe it springs back after exiting the barrel, but would that slight imbalance affect accuracy considering rotational spin?
Maybe, with the pressure uniform over the entire base, no flattening occurs.
What does the computer program say peak pressures are in the barrel?
I may be way off base with this and if so, don't be bashful about telling me!
I gas check when resizing after coating and don't have a lot of experience with rifle PC coated bullets, so I'm just tap dancing here.
It seems that the pressure from the powder burn would iron out the PC on the base of the GC, at least until exiting the barrel . Maybe it springs back after exiting the barrel, but would that slight imbalance affect accuracy considering rotational spin?
Maybe, with the pressure uniform over the entire base, no flattening occurs.
What does the computer program say peak pressures are in the barrel?
I may be way off base with this and if so, don't be bashful about telling me!
fiver
Well-Known Member
the Dacron was overdoing it's job.
a 100 fps gain is more than a grain of powder gain,,, even in the 223 unless your talking red-dot.
the best I can come up with right now is to do a deep, deep clean of the barrel.
like a JB bore paste type cleaning.
something isn't right.
look at that LEE bullet group.
IMO something is shifting the POI every couple of shots.
a 100 fps gain is more than a grain of powder gain,,, even in the 223 unless your talking red-dot.
the best I can come up with right now is to do a deep, deep clean of the barrel.
like a JB bore paste type cleaning.
something isn't right.
look at that LEE bullet group.
IMO something is shifting the POI every couple of shots.
Ian
Notorious member
You didn't see all the targets or you'd know how right you are about that. There for a while I was going out every day with the same ten rounds loaded the same way, setting up at 100 and shooting a group. Every few groups I'd try to get the zero right on the bullseye by adjusting from the previous day's group, but it never worked out because the core of every group was walking about 1/2 MOA or more in random directions. SInce it would still group (sort of) I kinda blew it off as the Vortex crosshairs andlight issues from day to day, or how I had the bags set up.
I did buy a box of 63 grain SMPs and part of the reason was to see if the system walks the groups around with jacketed or has the flyer pattern, and if the rifle will shoot sub-moa at all. Maybe it's time to find out?
What the Dacron did to the bullets has me scratching my head, too. When I saw the second shot go way out a giant exclamation point appeared above my head and I was very concerned about the next shot. When the next one barely hit the paper I pulled the bolt and suppressor to have a look for major leading, baffle strikes, or evidence of losing a gas check in the can, but nothing looked amiss. The cases looked fine, too. I did hear the fourth bullet strike something downrange but never found what. The fifth shot made a round hole in the mud flap just off the paper, but that's about all I could tell because the bullet hit the chain holding the plate inside the tire and disintegrated. It takes a lot of bullet mangling to get bullets to deviate more than 18" at 100 yards.
Hawk, the PC is almost as tough as the copper and a lot more flexible. I seriously doubt it will get flattened at all and am reasonably certain it isn't burning off. The splattered gas checks I've recovered from the steel plate backstop show the coating still mostly intact.