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paborn
05-27-2010, 04:38 PM
I have a 460350RFGC RG2 on order both cavities GC. Got a .460 sizing die from Buckshot. Will be casting for a Marlin 1895 Cowboy. Have mounted a Leupold VX-III 1.5x5 to do the load development, and have Skinner front and rear once I've developed two loads for working sights. I've a goodly supply of wheelweights and linotype, and just got around 7 pounds of tin. I've not been too concerned with expansion properties before with my cast in other calibers, but would like to make some good expanding hollowpoints at moderate velocities, and some maleable (not brittle) cast at higher velocities. If I understand my metallurgy from much research, if I match the tin and antimony percent (even leaving around one and a half percent excess antimony that is soluble in lead, I should have a maleable alloy that will expand if the velocity is sufficient.

If I have read correctly, straight WW with additional tin to get a 3-3-94 composition should give expansion and good accuracy to about 1700-1800 fps. From 1800-2100 fps, a composition of 5-5-90 (Lyman #2) should do the job. I have in mind two loads, a 1400-1500 mild shooting load, certainly adequate for deer, and a stouter, flater shooter load around 2000 fps. suitable for anything. Who knows, the wheelweight/tin alloy might work at the higher velocity with the GC boolit.

Again, the idea is to have loads that will not be brittle, and give expansion if velocity is adequate.

I have a good supply of RL-7 from my 30-30 projects, and I believe it will be as good as IMR 3031 which I have more experience with.

I figure I'l work around 40-46 grains for the lighter load, and 47-52 grains for the heavy. Any comments on RL-7 loads are appreciated.

From those of you with experience casting expanding 45-70 boolits, any comments would be appreciated.

PaBorn

Bass Ackward
05-27-2010, 05:13 PM
Nice write up based upon currently accepted metallurgy. You don't mention meplat size or hollow point diameter. Both affect your estimates. Tin balance with antimony generally guarantees the most malleable bullet. NOT to be confused with a pure lead and tin bullet.

I am going to tell you that it ain't that simple to narrow down to a hardness and velocity level. First thing to remember is that velocity in these terms is not muzzle velocity, but target strike velocity which is harder to determine.

What complicates the scenario is the material struck, and the angle of strike, plus the size of the hollow point. For example, If you strike on a 45 degree angle and have a cavernous hole, (weak olgive) there is a better than average chance that the nose will collapse in on itself and you will not experience the hydraulic expansion characteristics that you seek. The nose will simply break off to a wadcutter.

The good news is that you are in a good bore diameter to learn and cover mistakes. One might argue why you are even concerned about expansion anyway. And there are tricks to be learned that can improve expansion such as filling the nose with wax so the hydraulic effect doesn't have to wait for liquefied material to fill the cavity. It can also strengthen the nose just enough to allow greater shot angles.

Nobody can tell you with 100% assurity, you simply must walk this path yourself. And then there is edible meat destruction too. Everything is give and take.

paborn
05-27-2010, 06:51 PM
Boolit is the 460350RFGC on the group buy http://castboolits.gunloads.com/showthread.php?t=66018 I believe this HP design is the accepted more modern HP design (versus Keith type used for binary alloys) used with correct tin/antimony/lead compositions at higher velocities.
Yes, I agree, with a .45 hole in both sides of an animal does it really make a difference if the hole isn't bigger? However, if I cast 350 grain non HP boolits, I'd just as soon they were ductile (malleable?) and not frangible and break up if they hiit something solid. You will have to forgive me, as I'm an engineer, and engineers tend to be anal about many things. Just trying to product a HP that does what it was designed to do. Besides, I'm retired, live in an area where between three states I can shoot over 15 deer a year (the family likes venison), and I can reasonably field test terminal performance as long as it can be evidenced by shooting a deer lenthwise. I used to hunt the big bears and larger game but those days I think are gone. As an aside, both the brown bears I took in Alaska (years ago) were shot with a .338 Win with 250 grain Noslers and I never got a sample back to check expansion. Both shot under 50 yards with three shots, broken shoulders (the bear's). I believe I could have done the same thing with a 45-70 and 400+ grain cast boolit of an alloy that didn't break up. Something nice to dream about!

Thanks for the comments.

Paborn

Bass Ackward
05-28-2010, 06:14 AM
You will have to forgive me, as I'm an engineer, and engineers tend to be anal about many things. Just trying to product a HP that does what it was designed to do. Paborn


These comments were not meant to be a negative. And they have very little meaning to you right now. As you start dropping deer, the relevance of what I have said may help you to arrive at the place you want to be faster because it took me 20 years of playing around to decide that a 45 for deer (ours anyway) bordered on too much gun.

After all the trials, after the hard and wide up and down the velocity curve, the hollow pointing up and down the line. I had wound channels that went from a caliber sized hole, to holes that you could drop a soft ball into and not touch meat, to skinning and have the whole front quarters fall to the floor (hollow point to the front shoulder at 45 degree angle with multiple projectiles exiting with one up through the spine) when you were pulling off the hide. Only one strategy was quick and reliable.

My best results were with straight lead and tin to a muzzle max of 1400 fps with a respectable meplat. Or hollow point.

DLCTEX
05-28-2010, 08:19 PM
I agree that a hollowpoint is not needed on deer with that boolit, but experimenting is fun! I have hollowpointed some of the 460-350 RD and I'm impatient for deer season to give me an opportunity to try them. Hoping to try them on hogs soon.