Mold Modification Help

[R.M.]

I'm feeling kind of stupid here, but I'm sure somebody here can steer me in the right direction.
I want to reduce the weight of one of my .45 molds about 10 grains by skimming of the top, and for the life of me, I can't seem to crunch the numbers the right way to get an answer that sounds right.

TIA
R.M.

[OldBob]

I believe the formula is Pi*r squared*length*weight/cu.in=10 grains. Pure lead weighs 2870 grains per cu.in (.41 lb * 7000 gr/lb) so this works out to approx a .025 length decrease given a .430 dia pure lead bullet. That being said, I would measure a bullet, then file it down about .005 at a time until I had my figures double checked ! Your dia. and alloy are going to be a bit different, so the calculation isn't exact.

[44man]

Yes, I have to ask why 10 gr's is so important? A slight change in alloy alone can change a boolit more then that. I have a Lyman boolit that is supposed to cast at around 320 gr's but it goes 347 gr's and shoots just great. None of my home made molds come out right and it just doesn't matter. Boolit design and fit always is first, not whether it is a few grains too heavy or light.

[R.M.]

I cast for some of the guys at our club, which NRA bullseye is their main focus. They have it in their head that 185 grain bullets are better than anything else. Just trying to drum up more business

OldBob, thanks for the numbers.

R.M.

[45 2.1]

45 cal, 0.452" diameter would be a 0.022" reduction in length (on the major diameter) for about 10 gr. weight.

[OldBob]

Sorry guys, I had my head tucked where it shouldn't oughta be on the dia. Oh heck, .44, .45, they both get-er-done :mrgreen: :mrgreen:

[mag_01]

Lee has a 190gr swc---Would that get you closer to where you want to be ?

[R.M.]

The Lee 190 grain is what I'm using, but at 40:1, it's dropping them at 192gr. I want to keep at the 40:1 alloy at about 8.5 BHN.
I just bought another 6 holer off E-Bay, and the guy swears that it's a 180 gr. I didn't know that Lee made a 180 grainer. It should be here in about a week, so we'll have to see. If the profiles are the same, other than the overall length, I might make them same. Hafta see.

Thanks for all the help.
R.M.

[georgeld]

Try using bullet scrap for your alloy.

Thats what I use in Lee's 158gr .38 SWC and they come out right on 147gr.
and plenty hard.
But, I got four tons of the scrap so won't have to fight getting the same mixture again.

Just an idea, hope it helps some. I think they're trying to be picky and ten grains either way wouldn't make a spec of difference, nor would they even notice it unless they weigh the slugs. Jeeze!!

have fun most of all,

[David R]

you might want to pay a machine shop. If you take off the sprue plate and hold down, they could do it on a surface grinder. Have them true up the bottom first. You will get the exact amount you want off the first time.

David