Pyrodex and Triple 7

[Major Tom]

I would like recommendations for loading an original 45-70 trapdoor using a 500 grain soft lead bullet. Powder charges, weigh by volume or weight scale. Thank you

[lyman]

interested as well,


I've only loaded using 2400

[J.J.]

First off I would not recommend either Pyrodex or Triple Seven as a propellant. Swiss 1 1/2 Fg is what 95% of the target boys are using.
Make a sample round to determine your starting cartridge over all length by seating the bullet in the case until it just chambers. Then about .010" deeper. This is your starting cartridge overall length.

A good starting configuration for this cartridge is:
Cartridge case. (I use Winchester brass as it has a greater capacity)

Bullet: For the trapdoor it should be at least 500 grains and of 20/1 or 30/1 lead/ tin alloy. the trapdoor groove diameter can run from .457" to up to .465". The heavy alloy bullet had to be at least 500 grains so it would "slug up" to groove diameter when fired. This is why the Govt. adopted the 500 grain bullet over the 405 grainer.

.003" newsprint wad under the bullet in case there is a trace of bullet lube on the base of the bullet so the .030" wad will not stick to the bullet upon firing

.030" vegetable fiber wad under Newsprint wad.

Powder column.

CCI BR2 primer (suggested)

Using simple math determine bullet seating depth of sample round.(distance from mouth of case to base of bullet when seated)

Using drop tube (at least 24") slowly pour powder into case until it stacks to bullet seat depth + about .025" for slight compression when seating bullet Insert wads. The exact amount of powder will be determined by trial and error by measuring the distance from the case mouth to the top wad in the powder column with the rod end or your dial caliper. You can either go by volume or weight
63 grains by weight would be a good starting point.
Adjust as necessary by either adding or subtracting powder to adjust stack height. You can compress the powder column with the bullet about .040" without deforming the bullet base.

Once you have determined the correct powder charge you are good to go. Remember there should be NO air space between bullet base and powder and wad column.
J.J.

[Tuna]

The correct unit of measure for both Triple Seven or Pyrodex in weight by volume.

[J.J.]

All instructions above relate to Swiss powder. I should have stated same.
J.J.

[Major Tom]

Thank you to all who replied to my post. I settled on loading Alliant 2400 @ 22.0 grains with the 500 grain soft lead bullet.

[JimF]

Thank you to all who replied to my post. I settled on loading Alliant 2400 @ 22.0 grains with the 500 grain soft lead bullet.

When using that load, better to elevate the muzzle to orient the powder against the primer.

Even then, you can expect a dirty chamber/bore.

Way back, I tried this load . . . .did NOT like it!