Dr. A. I shot a 45/70 T/C Contender and have been playing with cast bullets in it for over 20 years. Mainly shooting deer with the RCBS 300 FN. GC. I cast mainly with wheel weights + 2% tin. The weight comes out to 330 grs.. 54 grs. of IMR 3031 gave me great accuracy. Before I went to an Aimpoint for hunting, I had a 4 power scope on the barrel, accuracy would hover around an inch at 100 yds.. With the Aimpoint my groups hover around 2 inches at 100, when I'm having a good day on the bench. But 3031 would leave a lot of unburn grains of powder in the barrel, when the next round was chambered the grains would jam up between the bullet's ogive and the throat, and the action would not close. So I used IMR 4198, which shot good but not as good 3031. Last fall I tried CCI 250 magnum primers with the 3031, that solved the unburnted powder problem. Had to drop back to 53 gr., the accuracy is still great, and the velocity is 1600 fps.
I've tried quite a few things with the bullets. wheel weights + 2% tin, air cooled, and aged at least 2 weeks, works very well. Tested into wet newspaper expansion is good down to about 1300 fps. Under 1300 fps to about 1100 fps., the bullets just kind of rivet up in the front to about 55 caliber. This works just fine, you really don't need to get that 'classic mushroon shape', to do the job. Kills deer good. I annealed this alloy. Put the bullets in a 350 deg. oven for a half hour, then turn the oven off, and let them cool, slowly to room temperature in the oven. The bullets are softer then the air cooled bullets, and they don't seem to age harden much, if at all. The mushrooms are a nicer at lower velocites, but in use on deer there doesn't seem to be much difference as compared the the air cooled bullets. I tried water droping the bullets, no expansion, letting the meplat do the job. In wet newspaper, penetration was about 48". With the softened, and the air cooled bullets, the penetration was about 15". The hard bullets killed deer good. I shot a deer broadside at about 175 yds., the hole between the ribs on the off side was about 1 1/8" diameter. The deer went about 60 yds. and dropped. Made some soft nose bullets, the nose was 5% tin in pure lead and the body was Linotype. Expandsion was good at lower velocites. At higher velocities the linotype would cut through the soft expanded nose. Killed the same as the wheel weight bullets. Tried pure lead and 5% tin (20 to 1). Expanded ok at higher velocity, but expandsion was not dependable at lower velocity. Even with a hollow point, some bullets would expand, some wouldn't. The accuracy didn't seem as good as with the wheel weight alloy. Killed about the same as the wheel weight bullets. I have tried hollow pointing the air cooled wheel weight bullets. I used a small lathe to drill hollow point of different sizes and depths. Also used different sized center drills. The bullets would expand big and quick but would lose a lot of weight. Deer shot at 100 yds. or less would have 4" enterance holes, not a nice sight. The pentration was not as great. By mistakeI hit a deer in the butt, the bullet penetrated from the rump, to,and through the off side front shoulder blade and stopped under the hide. The bullet lost 80 grs. of weight, the remaing weight was about 250 gr.. This is the only cast 45/70 bullet I've ever recovered from a deer. I didn't shot any deer with the hollowed pointed, annealed bullets. What I'm trying now is a soft nose bullet with nose of 2.5% tin in pure lead, with an air cooled wheel weight body. The soft nose is only about half the length of the nose, just enough to expand to 50 caliber. The softer wheel weight body does not cut through the soft mushroom like linotype does. This bullet gives a nice mushroom at lower velocity, as compared to the air cooled bullets. I haven't shot any deer with this bullet yet. I make my softnose bullets with a dipper made with wire and a cut down 357 magnum case. It's a pain to get bullets without defects. Bullets with soft noses will shoot to the same point of impact as without a softnose, so you only need to use the softnoses when you shoot game.
I make bullets for a friends 1895 Marlin. His gun doesn't like the air cooled alloy, groups run about 3-4" at 100 yds. The gun does like the hard water dropped, or an oven heat treated bullet. Groups run an 1 1/2" at a 100 Yds. He hunts in a thick area where his shots are about 40 yds., and almost always within a 100 Yds. He says the the hard bullet blows a golf ball size through the deer, and if they don't drop on the spot, they only go a few feet. I gave my friend some of my latest softnoses, with the wheel weight bodies, except I oven heat treated them to harden the body. He hasn't shot any deer with them yet. His load is 42 gr. of IMR 4198. We didn't chronograph this load, but I estimate it's about 1750 fps.
I think at the velocity you are shooting, a 400+ gr. bullet, cast of wheel weights and 2% tin and aged at least 2 weeks, would give you good performance out to at least 250 yds. I hope hope this information helps. Joe
