BPCR alloy

[guninhand]

A good sample alloy (using what you have) for the Money bullets cast in a 20 lb trial pot is the following mix.

3 lbs Lino
15 lbs plain lead
to this add only 1 oz tin

the additional tin will bring the tin total in the pot to about 1%. This is important - do not use more.

This ratio is quick and dirty and will make an alloy of about
97 Pb
2 Sb
1 Sn

It will have a hardness of about 12-13 and be time stable. This will support any BPCR Nose.

You can get out the calculator and scale but this will be close enough.

Used your formula, results perfect. Many thanks for posting.

[Chill Wills]

Used your formula, results perfect. Many thanks for posting.

Thanks for saying so!
(I missed seeing this until now. )

Are you casting for a High Bc bullet and have you shot it in this alloy yet?

[guninhand]

Thanks for saying so!
(I missed seeing this until now. )

Are you casting for a High Bc bullet and have you shot it in this alloy yet?

Am using the Buffalo Arms JIM459560M4, a "Money" bullet, not sure what real BC is, will get two chronos together and measure it for real in the spring. Probably won't get to shoot this alloy before then.

[Tom Myers]

Am using the Buffalo Arms JIM459560M4, a "Money" bullet, not sure what real BC is, will get two chronos together and measure it for real in the spring. Probably won't get to shoot this alloy before then.

Guninhand,

For what it's worth, the Precision Ballistics Software contains a feature that makes it possible to quite accurately estimate (As opposed to estimating a BC from bullet profile measurements) an average bullet Ballistic Coefficient between two targets at whatever range distances you can access.

I incorporated this software feature into the Precision Ballistics module after ending up with one chronograph when I started out with two chronographs.
Two important aspects of software vs. chronograph are price and the target range limitation of the chronograph setup.

You would need only a normal muzzle velocity chronograph setup, (The software will calculate the actual muzzle velocity), two targets at any measured range distances with precisely measured vertical group center from aim-point values and a micrometer to accurately measure sight height change between the two targets.

Click here for a Link to the on-line help file page keyed to the "BC from trajectory" feature

[BrentD]

You can also empirically measure (estimate - all things measured are estimates) a bullet's BC with one chronograph by simply measuring velocity of a particular load at two different distances. Simply shoot a number of rounds over the chrony at a near distance until you are confident of your estimate of average velocity and then move the chrony out to a longer, known, distance, and repeat. The two velocities can be then be compared over the known interval in between and a BC is quite accurately produced by the JBM website. The BC's produced this way have repeatedly allowed me to extrapolate from a 200 yds zero to any distance up to 1000 yds within 2 minutes of, and usually less. I typically do this by measuring velocities at 3 yds and 99 yds from the muzzle.

Using one chronograph has advantages (minimization of instrument induced bias) and disadvantages (requires more rounds to be fired), but without question, it works.

[Tom Myers]

You can also empirically measure (estimate - all things measured are estimates) ***************************.

Brent, you are quite correct. It was a sloppy description of the process. I'll amend it.

[guninhand]

Thanks Tom and Brent. I have the Ballistic software and it has a spot for BC calculation as is mentioned for the JBM web page. Was going to borrow a friend's chrony and use it at the safe end and mine at the riskier end, never occurred to me I could get by with just one.

[MaLar]

I used this alloy at the last two shoots I attended. The first was a wash but I expected that after the time I spent away from the discipline.
Had trouble with fouling and other things.
I've got all that taken care of. The last shoot I went to I shot a 20 not the best but I shot 2 animals out of sequence.
Plus the wind was quite strong that day doesn't help I have old peepers now also.
I just cast over 200 of the Lyman 410660 and most all were target grade. This alloy cast very well indeed.

Thanks for your help Chill Wills

A good sample alloy (using what you have) for the Money bullets cast in a 20 lb trial pot is the following mix.

3 lbs Lino
15 lbs plain lead
to this add only 1 oz tin

the additional tin will bring the tin total in the pot to about 1%. This is important - do not use more.

This ratio is quick and dirty and will make an alloy of about
97 Pb
2 Sb
1 Sn

It will have a hardness of about 12-13 and be time stable. This will support any BPCR Nose.

You can get out the calculator and scale but this will be close enough.