Possible to do a pound cast of my AR-15?

fiver

fiver

Well-Known Member
I know you can read about all of your questions right here on this site.
I know that cause I have typed all of those answers out.

here is specifically what I use in my AR-15's.
3 parts ww alloy, 1 part lino-type, and 2% more tin added.
the rcbs 055s mold and the HM-2 60gr mold sized to 225 and 226 respectively.
I weight sort to .1 gr groups, and visually cull like they owe me money.
22.5grs of IMR 4895.
LC cases cause I got a pile of them.
and wolf SR primers [because they are the most accurate]

I water drop the alloy and get a whopping 3 BHN increase, but still do it because it just sets the alloy.
if I wanted a heavier bullet [shrug] I'd just call Jared at arsenal and tell him what I wanted and have him E-mail me back a picture with diameters, than make the changes to the design I wanted and have it cut.
 
BHuij

BHuij

Active Member
Awesome, thank you for summarizing that for me. 3:1 WW:Lino is great, less lino required than I expected which mean I can stretch my lino out further.

If memory serves, the higher the tin content, the less the effects of water quenching, is that correct? I don't have any pure tin or known-percentage-tin alloy I can use to add your recommended 2%, but I've never had any trouble getting good fillout. Think I'm safe to skip that step?

I'm going to give this a shot for the next batch of bullets I cook up.
 
fiver

fiver

Well-Known Member
tin retards the quench effect.

do a small batch without the extra tin and see.
you'll be making an alloy similar to the teracorp magnum that the commercial casters use.
but you'll be out of balance and will see the brittleness of the higher antimony content.
it isn't all about the hardness.
 
Ian

Ian

Notorious member
or the fillout. It's about making an alloy with the squish characteristics and toughness needed for the particular application.

We need to come up with a quick and dirty explanation for ternary alloy percentages, what they do, when to use, what kind of throat/bullet shapes need what, pressures, heat treat characteristics, etc. There's so much confusion on this issue and it's key to success in anything past 1800 fps.
 
BHuij

BHuij

Active Member
So I have wrongfully assumed that the only purpose of adding tin was for a better fillout, when in fact the tin actually adds some toughness to the alloy, counteracting some of the brittleness caused by the antimony.
 
fiver

fiver

Well-Known Member
yes.
it ties everything together in a longer internal chain.
you don't want more tin than antimony for various reasons.
think about a nail and a screw when you pull a board away from another one.
the nail just bends then comes out.
try pulling a screw out, you have to break it or rip the board.
there are other analogy's of course and some are a lot better but your changing the entire inside of the alloy by adding or removing a few percentage points of this or that.
sometimes it isn't even a whole percent. .2 or .3% of some additives will add 3 bhn or a toughness not matched by 2-3% of other things.
but the nail and screw does illustrate the difference between malleable and hard.
the trick is to get somewhere in between, so the alloy does give and flex but without breaking [that includes breaking down internally]
we have all seen high antimony alloys crack or chip or whatever, but low antimony alloys actually allow the lead to bend and flex and flow under pressure.
extruded pipe and other products [like swaged bullets] have 3-5% antimony in them but are considered dead soft. [that's because the antimony crystals have broke down under pressure and allowed the lead to slide and soften even more than normal]
put a couple of % tin in the mix and you'll break the swage die..
 
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V

VZerone

Active Member
If you don't have tin the antimony won't, for lack of better words, blend with the alloy well. Tin helps hit and you only need a certain amount of tin for a certain amount of alloy. That old myth by certain people is to add two percent tin to EVERYTHING is wrong!
 
Rick

Rick

Moderator
Staff member
VZerone said:
That old myth by certain people is to add two percent tin to EVERYTHING is wrong!
Click to expand...

confused-face-smiley-emoticon.gif

Well dang, I'll be sure to let the metals industry know right away that they have it all wrong, I'm sure that knew knowledge will fascinate them. Other than that I don't think I've ever heard ANYONE say add 2% Sn to EVERYTHING. What the metals industry does say is to add no more Sn than the percentage of SB.
 
Ian

Ian

Notorious member
Fiver, that's exactly the sort of explanation I'm trying to capture in the alloy article, hopefully without making the descriptions too complex. Basically make a short explanation of dendrites, what they are, how the tin and antimony affect the lead dendrites and change the structure, and how all that relates to the physical characteristics of the metal under pressure. Basically what's in the Lyman #3 cast bullet handbook but condensed and then applied to what the bullet needs to do in the throat and how tweaking the malleability, or the ductility of the bullet metal to help the bullet in the ways it needs to be helped gets better groups and extends velocity capability.
 
fiver

fiver

Well-Known Member
do you know how many times I had to read that section of that book.
I ended up buying another copy and giving the first one to someone getting started in reloading in a 3 ring binder because the book was falling apart from me opening and closing it so much.
 
BHuij

BHuij

Active Member
Great explanations all around. Thanks all. Now I just need to find a cheap source of tin alloy of a known percentage...
 
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