Design and alloy, part II

[Ian]

I need everyone's help and input here. Following Fiver's "design and alloy" thread that was intended to get the brain juice flowing among the high-velocity crowd, I'd like to compose for our readers a reference article for the read-only section regarding specific properties of ternary Pb/Sb/Sn alloy as it relates to HV cast shooting in rifles (and possibly zinc and copper-enhanced alloy too, maybe a separate one for those though). I'll compose the article here in the OP and keep editing it with additional input from members who will be credited for their contributions. If you have your own ideas along these lines, write it up and post it here.

The items I'd specifically like to address in the article, subject to additional input, are:

#1 Philosophy of launch: The particular alloy characteristics that are needed to achieve a straight start in the barrel, considering various rifle throat shapes and bullet styles. This will include how to work with various lube groove designs, nose bump and when it's needed, neck clearance and how to work with it, tapered and 2D bullets and the differences alloy makes with each.
#2 Alloy composition: How to achieve, through blending and heat treating, the characteristics needed in #1. Details of what each alloy component does so that the reader can better understand when they might want to try using more tin, or lower antimony and higher heat treat, etc.
#3 Leading edge failure: Discussion of the secondary HV challenge, which is constructing an alloy which will withstand high surface speeds and the force of standard rifling twist rates without experiencing abrasion failure. This excludes the companion subject of rifling condition/quality, which has been well-covered by others.

I'm looking for input with specific, empirical examples of what works as well as what doesn't, so the "why" can be inferred or offered as reasonable explanation. .22 to .35 caliber seems to be the area of interest, with 22 and 30 seeming to get the most attention on this board. If you have a quick example that can be inserted into the article then please feel free to throw it out there, particularly if it will demonstrate the effect that a specific alloy change or bullet shape made to improve groups. I'll start pecking away at a composition as I have time and inspiration, right here, below.

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[Rcmaveric]

Nothing to add. Following out of curiosity. Interested to see what benefits zinc brings to the table. Would also love to see detailed write up on the various ways of adding copper that dont envolve expensive babbit alloys.

 

[VZerone]

Does ideas mean assumptions and theories? Someone that knows all this needs to write this up. No, it's not me.

Zinc is going to make the alloy harder with just a very little addition of it. If you add too much you screwed the pooch!

 

[fiver]

it would be more like experience from observation.
your not going to find a scientific paper written on any of this stuff.
but then again Dr. Mann, Elmer, Mr. Pope, and that one guy that invented gas checks was just doing home type experiments too.

 

[Ian]

Yes, exactly, experience from observation.

Let me reiterate a few things. I asked for empirical data, that's the best any of us home-gamers can do and all I can provide myself. Copper and zinc enhancements are not the topic here, but deserve their own discussion to build on this foundation; there is at least one pretty much "in a nutshell, all you need to know" post involving a certain type of Rotometals babbit and other constituents for copper-enhanced rifle bullet alloy on this board, if someone remembers and wants to expound on it, that alone should be in the reference section for its extreme merit in a world of fragmented and inconclusive information. Also, the idea here is to put out some information, together with some guidelines from which to operate ("this worked for me" kind of stuff), for those who are looking to gain a better understanding of "bullet metal" and how to manipulate percentages to specific ends for specific tasks. This isn't to be another theoretical rant, it needs to be fact-based and direct with some philosophy thrown in to pull the concepts together, otherwise it's just more confusion and argumentation, which doesn't help anyone learn anything about bullets.

Glen Fryxell has written at least two very informative articles on the subject of alloys, from the physical/chemical science standpoint and from a shooting characteristic standpoint, but neither was intended to address the subject in the context of alloy for making go-fast bullets for rifles. I'm trying to fill a gap.

If you or someone you know knows and can put in print the characteristics of tin and antimony in various percentages in lead alloy and can describe how to blend for specific purposes, please contribute! If there was any meaningful, non-copyrighted reference material on the subject, or prior work by ordinary shooters who would share, that would help here because I don't have enough yet to write a definitive article on my own.

 

[fiver]

tin and heat will pull copper into solution.
the key is to use clean oxide free copper and get it under the surface to melt.
or to melt it and pour it in the alloy and use tin to keep it there.
the thing is copper works on the boundary of antimony but our at home methods means tin to get it into solution.

 

[Tomme boy]

What would silver do?

 

[Brad]

Based on periodic table I would expect silver to do similar to copper. It just does it at a higher cost. I know I can't afford to make a .3% Ag alloy!

 

[fiver]

it is similar to copper but in a different way.
it doesn't form a boundary layer around the antimony, it acts more like tin does only without the wetting on the surface.

 

[Brad]

Here ya go. This is the 30 XCB I recovered from the 100 yard berm Tuesday. It had a MV of 2400 plus fps. Figure impact velocity of at least 2000 fps.
If it had been something like Linotype I would have found a small shank with the nose washed away.

Anyone care to guess the percent of weight retained?

 

[Rick]

135 gr.

 

[Brad]

Damn close.
140 gr of a 162 gr bullet. Like 86% retained weight. Most jacketed bullets won't do that.

 

[freebullet]

I'm impressed you even recovered it.

 

[Brad]

I'm a pretty good digger in the berm. My eyes are well trained to tell new from old bullets. The berms are finally drying out enough to be of use.

 

[fiver]

I kind of kicked and scuffed around in our berm last trip but didn't find anything.
we got too many rocks in the dirt.
it's easy to see where they went in from the trough they dig, but there is always a rock in there somewhere.

 

[freebullet]

I'm wondering how many bullet buckets it would take to capture some at those speeds, relatively undamaged. I think 3 would do it, my current one at the end, with a second having 3" of sand in bottom filled with rubber mulch, & a third in front with just rubber mulch with carpet at the ends.
It's about slowing them down with little disruption.

 

[fiver]

the nose shape will make them penetrate pretty well and the speed would surely contribute.
I would say at least as far as and maybe/probably further than a jacketed bullet at about the same speed.

 

[Ian]

I've been wondering that myself. I have some 6" PVC well casing, some 6" steel casing, and plenty of places to build a wooden trough with dividers and leave it set up permanently. I used to have access to an unlimited supply of sawdust and used oil, now just the latter, but it always worried me about being a fire hazard. Maybe 10' of oiled sawdust followed by 4' of crumb rubber?

 

[Rcmaveric]

Make a plywood tank and shoot into it. I was researching plywood tanks awhile back when building my aquarium. Richard Lee shot into a swimming pool to recover his bullets. Three to four feet of water will stop about anything. Steel water tank is what the phorsenic guys shoot into to recover undamaged bullets.

 

[Intheshop]

Very slight tangent alert in a cpl.directions.

Was researching some Reed & Barton silver,"the" Isaac Babbit was instrumental in forming this co in the 1820's.

#2,be dang careful dismissing info or research just because there dosen't "seem" to be a connection or it's not titled specifically "CAST BULLET ALLOY SPECS".Meaning,and not an excuse,by looking at mister's,Babbit...Reed....Barton,one of the things you're trying to identify is manufacturing techniques.As they would lend themselves very nicely to homeboy efforts today.When helping grad students in historic pres,I call it "edge work".Good luck with your project.