Will alloys of identical BHN act any different?

[Neverhome]

The title says it but, hypothetically, if one had several different alloy makeups and all had virtually the same weight and bhn would/could the INTERNAL ballistics be any different? Talking all other things being equal and perfect gun and perfect shooter. I am and have neither.

Examples,
Alloy 1: Electrotype 95/2.5/2.5 BHN 11

Alloy 2: 6 pounds pure + 0.5 pounds Pewter 92.3/7.12 sn/0.46 sb/0.12 cu This is assumed obviously as pewter makeups vary. BHN 11

Alloy 3: 11 pounds pure + 1 pound tin 91.7/8.33 BHN 11

Alloy 4: 96/1 sn/3 sb BHN 11


I'm aware from testing that TERMINAL ballistics will be different. I'm only talking about the INTERNAL ballistics here.
Also, I personally doubt I'm a good enough loader or shooter to test this myself furthermore it would take way more components than I'd like to expend to make any test statistically meaningful.

Thoughts?

[guywitha3006]

Following...curious to see peoples' experience.

[Neverhome]

Only thing I can think of that might have a bearing is the possibly different frictional coefficients of different alloys. More friction/more pressure and vice versa. I've been searching for the frictional coefficients of babbitt materials thinking that might be info that is floating around out there but unfortunately the hardnesses of different babbitt alloy are not readily available. Still looking for a comprehensive list of coefficient of friction vs Babbitt alloy also.
I did find reference in a NASA study of crystalline tin structures affecting CF. Made me think that if crystals in tin affected CF then shouldn't the very obvious crystals in bullets containing antimony affect CF. What about frosted vs not frosted?
I know if this has ANY affect on internal ballistics it is certainly less than the difference between lead vs jacketed but it's an educational opportunity. I'm just curious.

[Larry Gibson]

......different alloy makeups and all had virtually the same weight and bhn would/could the INTERNAL ballistics be any different?

Assuming they were cast in the same mould, the same sizing, the same lube, the same GC and were loaded exactly the same with the same load then; no, there would be no real measureable difference in the internal ballistics.

[Rcmaveric]

I second what Larry said. I don't think internal ballistics will be noticeable or measureable difference. The affects after impact is what will be noticeable.

[runfiverun]

pressure on the antimony alloys will act differently than pressure on the tin alloys.
both internally and externally.
antimony crystals will break down under pressure and allow the alloy to flow easier.
that is why it is used in extruded lead products and for swaging
tin is not used in extruded lead products nor for home swaging, it's internal alloy makeup resists linear forces. [you can actually break a swage die with a high tin alloy]
it doesn't bend and flex well, it has to be bent and broken.
that's why you hear creaking and popping when you bend a high tin alloy [pewter]

[Neverhome]

This is mostly academic obviously but I bet any differences in flow properties or friction could be seen over the chronograph if one were to shoot a series with an alloy at xx hardness and then a different but same bhn alloy. Same goes for using a pressure trace. It would take SOME of the shooter induced variability out but you'd still have to make some assumptions about the consistency of the loading/casting technique.

[runfiverun]

you'd never see it on target from a revolver. [or at 30-K]
stroke it down the barrel at 2500 fps [pushing 50+K] and it will make a difference.

[Springfield]

Seems to me if they are different alloys then the weights could not be exactly the same.

[bgmkithaca]

I noticed babbit mentioned in one of the posts. I don't know how the friction co-efficients would apply compared to other alloys but years ago I made machine bearings that were cast from babbit and as long as they were kept lubed they wore very well-some of the stress loads on those bearings were quite high but they stood up to the environment very well for what it is worth to the discussion.

[Neverhome]

I noticed babbit mentioned in one of the posts. I don't know how the friction co-efficients would apply compared to other alloys but years ago I made machine bearings that were cast from babbit and as long as they were kept lubed they wore very well-some of the stress loads on those bearings were quite high but they stood up to the environment very well for what it is worth to the discussion.

I brought up babbit because since it is bearing material I thought maybe I could find actual coefficient of friction data. Then MAYBE if that data could be found for different babbit alloys I could scale it to help with the discussion at hand. Didn't find that data in any sort of form digestible to anyone but a tribologist.

[Grmps]

curious, alloy 1 and 4 don't add up to 100%

There has been some experimenting with copper to make rifle boolits more elastomeric, but that shouldn't affect internal ballistics

[Neverhome]

Im a numbskull. Thanks. Fixed it.

[reddog81]

Seems to me if they are different alloys then the weights could not be exactly the same.

That's exactly what I was thinking. You can get the same BNH using a variety of alloys but the weight is going to vary. I have no idea what the impact on internal ballistics would be but I imagine it would be fairly small.