Medium Bore alloy suggestions

[onesonek]

I'm looking for suggestions for an alloy to be used in .375-444. 265 grs. in weight FP w/.20 meplat, thinking about 2200 fps out of the Encore 24" barrel. And also what treatment if any (wq, ht, ht & anneal nose, etc.).
I have some thoughts of my own, but would like to hear other's as well.
Thanks

[onondaga]

Gas checked boolits at 14 - 15 BHN , the Lyman #2 alloy would be fine. If your boolits are plain based with no gas check a harder alloy would be better at 2200 fps.

Mainly, the bullet fit is more important than the alloy hardness with gas checked bullets, but with plain bullets , the alloy has to be up to the pressure and velocity so likely an alloy about 20 BHN would be needed at 2200 fps on non- checked bullets .

However 20 BHN is a poor choice for hunting as it has zero to no expansion on meat at any velocity and may even shatter.

My .458 Win Mag with 340 gr plain based bullets hold peak accuracy at 1610 fps, but higher in speed, groups begin to open with my BHN 14 alloy. I have a CheckMaker on order for this plain base bullet and hope to increase velocity to 2000 fps and maintain accuracy with the same alloy but gas checking bullets.

If I really wanted to go above 2000 fps, I would use a harder alloy than BHN 14 even with gas checks, maybe BHN 16 would be fine for gas checked bullets at 2200fps. That would be my estimation if you need that speed. Plain base bullets at 2200 is pretty hopeless for accuracy without gas checks and a hard alloy.

Those hardness alloys 14-16, even 20 BHN can be alloyed to not need water dropping or heat treatment. Heat treatment and chill hardening of lead alloys is not real permanent anyway. After a year or so they get nearly as soft as cast hardness anyway. So it is best to really alloy what you need so it will stay there in hardness.

Something like Linotype Alloy Ingot (4%-tin,-12%-antimony- from RotoMetals, linked at the page top can be alloyed with whatever soft scrap or wheel weight alloy you can get to mix an alloy of any practical BHN. Straight Lino can be shot at factory ammo velocities with a perfect bullet fit of .002" over slugged groove to groove bore diameter and good bullet lube. Of course, Lino really shatters on meat/bone impact, but that does not matter for paper punching ammo.

Lyman all purpose #2 alloy was really named very well, I stay near that!!! I mix that alloy with 7 pounds Wheel Weight and 3 pounds Lino to consistently get BHN 14 tested, 7days after casting as checked with my Lee Hardness Testing Kit

Gary

[onesonek]

I was thinking along similar lines Gary,,,and yes the boolit design is for gas checks. I forgot to stipulate that in the first post. I have a fair amount of lino, co-ww's, and iso alloy's here to blend and experiment with. I was planning on saving the WW's for slower use's, and use blends of the lino and iso for this faster application. But yes, alloying close to a Lyman #2 or Hardball is where I was figuring to start. Or maybe a 1 to 1 lino/iso will work as well, which looks to be about a 90-7-3, if my calculations are correct. As for measurements,,, my throat on this barrel, is .3765", due to the land groove configuration, I couldn't get a good read on the groove, but suspect it's .374"-.375". I'll size to the throat, and seat to bumping the leade.

[303Guy]

I've taken to adding a tiny amount of copper to my alloy with the belief that it toughens the alloy without hardening it much. With the right amount, no heat treatment seems necessary. (Too much causes poor fillout I think).

[onesonek]

Yeah, I thought about that as well 303. I bought a pound of "Super Tough" #3 Babbit from Roto sometime back, thinking some day I may want to experiment with added copper. This alloy is supposed to be roughly 84-8-8 sn/sb/cu. From another reading (not sure where anymore), it sounds like one wants to keep Cu under .2% If I use an iso/lino ratio, of 6 to 4 ans 2 oz. of the ST #3 Bab., I come up with a rough 89-6-4-.1 That would put me roughly up in that 16 bhn range Gary spoke of,,,,,if necessary.
Alot depends on what this Lino's composition is, as it's not new. Testing the ingots, it runs about 19.5bhn on the Lee. That seems well under the norm, but then I understand ingots will test different than boolits also.
As a side note, my initial alloy I have been using for the .45-70 and .454, has been a 1-1-1 lino/iso/ww mix, which was air cooling at 14 -14.5 bhn. Straight ww's would likely suffice for either of those. And that would conserve on my lino supply in which to use in this slighty higher speed situation.