Lead-free bullet casting alloy

[Ian]

CoG thing is the same regardless of alloy. Miller changes a little because of density/length but it's in stability's favor.

The whole problem with Bismuth alloy is Bi is incredibly crystalline and brittle. The shear planes are the size of coins. Everything we add tends to refine it some, but the relative scale is still working against us. Lead is mush and we have to add stuff to reinforce it and then add other stuff to make the reinforcement mesh finer and tougher and other stuff still to make it cure better, but with Bi we only have slightly less tough stuff to add to it to refine and soften it and really it all becomes a game of controlled fracture.

I edited a little better photo here of the 88/12/.75 alloy's broken surface compared to 73/27/.56 after adding tin. This lowered the melt point about 100 degrees which makes it unsutable for shooting, and it was still brittle, so grain refinement isn't the whole key here to making Bismuth ductile. I really think dhat for practical purposes the 88/12 with a dash of Sb is as good as we're going to get, or at least as much effort as I'm willing to put into alloying at this point. What we have here is easily cast, sized, shoots well, and is ductile enough. The rest we can work around with bullet design.

 

[fiver]

yeah,,,
that whole more tin lowering the melt point thing is something I'm still trying to wrap my head around.
all I really can see is that the tin isn't acting like tin at all [except maybe still acting as a wetting agent when cast]
I don't think it is really binding with the bismuth, more like just flowing around filling in the gaps like you mentioned earlier.
I know it took 5% for the effect to become noticeable in the earlier shot testing just to make the bismuth not break down under acceleration in low pressure lower velocity cushioned starts.
my theory there was the sinewave of the powder was actually the culprit breaking down the bottom layer of shot pellets, then the mass of the payload setting back on acceleration was finishing the job.

design was something I was thinking earlier.
minimal lube grooves and just about no nose length would probably be best for this alloy.
the trick will be making that happen and still have some aerodynamic efficiency.
the 22 won't be so bad to design [heck,, that multi-groove lyman with the grooves removed shrug?] but anything fairly heavy in a 30+ cal will take some creativity.

 

[Ian]

I have no doubt that a pointed nose would shoot just fine, the problem is terminal effect when it gets there. That's why I kinda wrote off the .30-caliber for deer and larger animals, I think it would need to be a Ranch Dog WFN and going fast to do the job well on large deer, and light bullets with big meplats lose energy quickly. Might me OK for the .30-30 or .308 at 150 yards or closer. Sure, you could probably kill a deer just fine with a hard, spire-point bullet, many humans and other things have died from the effects of steel-core 7.62x39, but we all know why that sort of projectile is a last choice for hunting edible game. I think the big-bore RFN bullets will shine with this alloy.

 

[RBHarter]

Sorry mechanic thinking . I'm not throwing stones or trying to poke holes .

XCB or one of the other similar designs to start in 30 cal . Maybe the 301618 opened up to .310 ?

Sine waves are out of my pay grade but I understand the function/results of them .........if that makes sense .

 

[Brad]

In 30 cal going to want a 165 gr RD minimum. The RCBS 180 FN wouldn’t be a bad idea either. Both need to be driven hard. A 400+ 45-70 would be great. I can see where the Lyman 375449 would be good too.

 

[Ian]

Hey, no apologies necessary, mechanic thinking has solved as many problems as engineer thinking ever did, and mechanics solve the final problems engineers create so stuff can actually WORK, so I think it takes a little of both.

If it weren't for some bona-fide scientists we wouldn't have gotten this far, but in the end it takes right-brained thinking to visualize what is happening in the bigger picture and see what specific areas the eggheads need to address. The same applies to regular, lead-alloy cast bullets except all the engineering is done and mostly understood, we just have to figure out how to put it all together.

 

[fiver]

partially the XCB would work... it would just come out with the original nose design [accurate type] and be shortened back to about 140grs.

look real close at the picture of the recovered Bullet Ian showed.
we are dealing with an extreme amount of alloy flow. [slump from the base]
because of the crystalline nature of the alloy, not because of the ductility of the alloy.

not that we don't have any with other bullets and a normal lead alloy,,, we do and plenty of it.
that's why some of us have design preferences that are not made by Lyman unless we are just going bang poof for fun.

 

[Ian]

The downfall of the NOE 30 XCB bullet, and also MY 30 XCB design which preceded it (Accurate 31-190X) is that they have tapered noses but lack displacement grooves in the area where a lot of metal needs to be moved. That factor creates extreme stress loads on the base of the bullet due to force needed to cram that matching taper through the throat. The load on the base creates distortion and as Larry discovered, base band wash-out and limited accuracy capability when using too hard of an alloy at high pressure/velocity.

The Eagan MX3 design provides a great combination of static fit, dynamic support, and easy displacement for a low-stress launch.

 

[CZ93X62]

THIS. IS. AWESOME. Time to buy some metal, methinks.

 

[fiver]

the bigger issue after the alloy flow is like Ian mention is where to put it.
think about this.
if you put a groove there to take up land displacement or to deal with trailing edge failures you just created a weak spot to be compressed by alloy flow.
on the bright side,,, the bases will be squished up square [hopefully] long before they get to the muzzle.

you could deal with some of it by using very shallow lube grooves placed along the drive band surface.
initially I was thinking lee TL type grooves but I don't think that would be best unless another groove or two were added, or if designed expressly for powder coat.

the key is to take advantage of the alloy flaw and not to fight with it.

 

[Ian]

the key is to take advantage of the alloy flaw and not to fight with it.

Exactly. This alloy tested between somewhere around 18.6 to 19.4 bhn with my Lee tester....but under fire it squishes up like sticky wheelweights and yet is tough enough not to gas cut or strip the rifling. Really strange behavior to work around. Thing is, the targets tell me that it works in spite of all the scrunching and bulging as long as the bullet has the support it needs, so I'm not too worried about finding solutions to these perceived issues.

However...we need to underline these characteristics in red and reference them often when developing other loads with othe bullets in other calibers.

My next thing to test will probably be either more of same or bump the velocity a bit and ease the launch pressure with 3031. Probably not going to test PC much more because that limits the useability for those who aren't set up for it. I'd really like to test the Accurate 45-297s in my NEF also, that will be a good test of lots of things like plain bases, fast powder, and bullet integrity in wetpack.

Aaaaannnd I need to put together a report for Rotometals.

 

[Ian]

THIS. IS. AWESOME. Time to buy some metal, methinks.

You'll have to either make it from scratch (shouldn't be difficult to melt it all together if you have the ingredients) or ask Rocky at Rotometals to have the lab put together a batch for you just like what they sent me. It's their house blend 88Bi/12Sn with .75% Sb thrown in. I have no idea what the cost would be but hopefully they'll sell it for the normal price and add the Sb alloy for cheap. Tell them you're following up on the tests Ian fom Texas is doing and actually are a CA resident and hunter and they might cut you a break on a few pounds. I'd say five pounds is a minimum for a bottom pour pot and probably will need at least ten to ladle it with a Rowell (one L or two?) Although after casting with it I'd say a shallow spoon with a spout bent into the side would be good enough.

The best casts I made were from a cool mould, so a big sprue is totally unnecessary and the focus is more on keeping the mould from getting too hot rather than hot enough as we are used to with lead alloy. A bottom-pour pot is very convenient but ladling with a spoon would work far better than it does with lead.

Fluxing is also...interesting, so the less exposure to O2 the better, hence my recommendation for using a bottom-dripper.

 

[CZ93X62]

OK, got that. I am leaning toward getting a Lee bottom-pour to use exclusively for this purpose. Mostly I am concerned about metals cross-contaminating in the furnace or on tooling--what metal(s) were your mould(s) made of, and did the 88/12/<1 alloy leave behind any deposits or affect the cavities in any way?

 

[Ian]

Segregating tooling would be a virtual requirement to ensuring 100% compliance. The moulds don't get hot enough for the metal to stick to them, in fact the lead-free alloy didn't even remove the traces of previous "tinning" on my moulds. Wash and cast is my recommendation. I used steel and aluminum and would not hesitate to use brass as I think brass will wick the heat away better.

 

[fiver]

I'd want a broke in brass mold.
they have that tinning thing going on that might pose an issue until then.

airc roto has free shipping if you break the 100$ mark.
probably not too difficult with the price of this alloy.

 

[Ian]

Got another test out if the way, this time with the .45 Colt NEF carbine that my friend Jim cut to 16.5" and threaded for me for a suppressor before I had my own lathe.

Gosh they look like lead bullets!


And at 50 yards we get a way high shot and then I crank the elevation a bunch and got 8 into a group.



Compared to lead alloy, same mould, powder coated and lubed with an earlier version of this lube:



So again I'm seeing slightly better accuracy than I ever got with cast, lubed, or PC'd in this rifle just like the .223 was indicating from just three groups. No special tricks, just cast, size, lube, load, and shoot with the same die settings.

I put the last one into the trap and it went through three feet of sawdust and into the cardboard box full of crumb rubber mulch acting as a runaway ramp at the end. Other than rifling marks, a tiny bit if base edge chowder, and a shine, it looks unfired:



I don't see why this wouldn't work just fine in a .45/70. I may pump up the charge to Ruger Only levels and shoot a wet Grainger catalog or something, but it's time to cook some venison steaks and have the parents over for supper.

 

[fiver]

those rifling marks..
but it works that's for sure.

wonder how a water jug would do, the sawdust and rubber didn't hardly phase it.

 

[Ian]

This rifle always skids the bullets a little, no big deal. Interesting that the 19-ish bhn alloy doesn't hold on any better than 10 bhn 50/50, even with powder coat.

Water jugs can be done easily enough. How many to stop 262 grains at something like 900 fps?

 

[fiver]

6-7?
maybe stop in 4 but I wouldn't bet on it.

 

[RBHarter]

9.0 Unique under the 452-255 @ 265 gr exits 2' of pig through 2 ribs and over an inch shield just shy of 50 yd ...... Just a guide probably take 5 to trap one .