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View Full Version : Hard to test accuracy with two different alloys!



Irascible
01-27-2012, 01:38 PM
I sold my 4 cavity H&G mould as it only cast .357 dia from WW + 2% tin (I needed bullets at .358 dia.) I bought a Lyman 358156 and an RCBS 38-158 SWC. The RCBS mould casts too big to take the GC with Lyman #2 alloy, WW+2% or straight WW (I did send it back once). I had to go to 8WW/2Lead+2% tin in order to get it small enough. (instruction sheet says use 1 in 10 for pistol bullets and 1 in 20 for cowboy bullets and Lino for rifle bullets!). So I cast a bunch and put them aside. Then I cast some Lyman bullets with the same alloy. They cast too small at under .358. So I have to use ww+2% or #2 alloy. Annoying. So now I have two different 357 mag bullets I have to cast with different alloys. It will be Interesting testing the results for accuracy. I'll never know which design is better nor will I know why. Actually it probably won't make a difference. Which ever one is more accurate is the one I'll shoot all the time. Actually, I'm pulling for the RCBS as I'd rather have the softer alloy. Leading shouldn't be a problem with either with the use of the gas check. All in the fun of bullet casting:>)

stubshaft
01-27-2012, 02:09 PM
Understanding that the alloy composition can have an effect on the diameter of a boolit in no small caveat. There are many who have not garnered that basic concept.

BTW - my money would be on the 358156.

runfiverun
01-27-2012, 03:20 PM
i would have just lapped out the h&g mold.
that will work on the mold you have to change alloys for now.

HangFireW8
01-28-2012, 12:41 AM
I sold my 4 cavity H&G mould as it only cast .357 dia from WW + 2% tin (I needed bullets at .358 dia.)

Just curious, did you have leading at .357", or is the need for .358" just your starting assumption? Also did you try a little less tin (or better yet, a lot less tin? See below).



I bought a Lyman 358156 and an RCBS 38-158 SWC. The RCBS mould casts too big to take the GC with Lyman #2 alloy, WW+2% or straight WW (I did send it back once).

Did you try expanding your gas checks with a hammer whack on a large ball bearing?




I had to go to 8WW/2Lead+2% tin in order to get it small enough. (instruction sheet says use 1 in 10 for pistol bullets and 1 in 20 for cowboy bullets and Lino for rifle bullets!).

Yeah, don't you love some of these assumptions of mold makers? They seem to think we have an infinite supply of alloying materials. 1 in 10 is just a waste of expensive tin if you have even the slightest amount of WW (antimony) available. The only reasoning behind this (Lee does it too) is tradition, their drawings are based on the shrinkage of some ancient standard, and they just keep using it.



So I cast a bunch and put them aside. Then I cast some Lyman bullets with the same alloy. They cast too small at under .358. So I have to use ww+2% or #2 alloy. Annoying.

Here's where I'm having a hard time following you. You say you "have to", does that mean you've tried ww+2% or #2 alloy and they come out at .358, or you're assuming that's what you'll have to do?

I have to point out here that very large amounts of tin can result in significant shrinkage, the opposite of what we think of when we add a small amount to improve fill-out. I learned this the hard way, when I accidentally mixed up a very high percentage tin mixture. The lesson was reinforced later when I made some ingots out of 60/40- they ended up having huge shrinkage holes in their backsides as they cooled.

Because we all work with mystery metal, it's quite possible your WW+2% or Lyman #2 is running a much higher percentage of tin then you realize.



So now I have two different 357 mag bullets I have to cast with different alloys. It will be Interesting testing the results for accuracy. I'll never know which design is better nor will I know why. Actually it probably won't make a difference. Which ever one is more accurate is the one I'll shoot all the time. Actually, I'm pulling for the RCBS as I'd rather have the softer alloy. Leading shouldn't be a problem with either with the use of the gas check. All in the fun of bullet casting:>)

I fully agree with this one- we all work with some degree of uncertainty about our alloys, and as the Lyman manual points out, even store-bought Certified lead alloys often differ from their specifications when laboratory tested. In the end we go with what works, and hope we can reproduce it.

HF

Irascible
01-28-2012, 02:36 PM
Well, I wasn't confident enough to lap the mould. It was worth too much as it was.
I should have said "I guess I'll have to use ww+2% or Lyman #2"
WW+2% is pretty much what it says. Lyman #2 is closer to 9% tin. They both produce larger bullets than my 8/2 +2% or 50/50 +2% ww/lead alloys.
Even at the large percentage of tin in Lyman #2 I don't notice more shrinkage than my other WW + 2% alloys. It may, but I haven't noticed it, nor has it caused a problem.