I handload for 30 calibers, and they all seem to wimpy, except the 45-70. I have a little plastic stocked handi rifle that kicks me into next week with Trapdoor loads.
So instead of developing a more powerful load, I have been working on better wimpy loads for the 45-70.
1) 40 gr IMR4895 and 405 gr lead is a Trapdoor load.
2) 30 gr instead works fine, kicks like a 30-06, and is accurate too.
3) The button bullet described in:
http://www.recguns.com/VIIE7.html
can be had from Liberty or Western:
http://missoula.bigsky.net/western/
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4) The lite loads I have developed for shooting on 5 acres with neighbors use even less powder. I have been shooting .454 lead balls with polymer wads I cut, with 1/2 gr Bullseye.
An interesting thing came out of this development. I pushed the ball down into the case and compressed the powder. The load makes the same amount of noise as before, but now goes through 1" of wood instead of bouncing off wood. The price paid for this is in accuracy and peak pressure. Who cares? This is a short range, low pressure load.
5) Also, a good source of 45-70 lite load is "Lyman 41st" 1957. In that old book there are 36 loads for the 45-70, like:
146 gr 5 gr Unique for 50 yard target
250 gr 19.5 gr 2400 for 200 yard target
345 gr 40.5 gr 4198 for bear