I have purchased a box of 325 gr. 45-70 bullets and will be trying them out to see what kind of accuracy and velocities I can get. How about we use this thread to track the progress of all of us that are going to try this?
I resized some of these today, using a Lee bullet Sizing die (.452). It took tremendous effort on my press to resize these. The were harder to do than the 400 gr. Speers. I would suspect that the jackets are thicker on the 325's. I even had to pound out a couple of them out of the die. I do use a lube -- Imperial Sizing wax. Make sure you remove all copper and lead from the inside of the die before you try re-sizing. Especially lead -- you can fuse the bullet to the die (like I did).
The length of the bearing surface of the 325 is about the same as the Speer 400 gr. The bullet length of the 325 is 1.115" versus the 250 gr. fxt is 0.995". MEANING that case capacity is reduced by 0.12" when using the heavy bullet. Note that the overal loaded cartridge length for both bullets is 2.25".
Since the case capacity is reduced using the heavy bullet, using slow powders like 1680 may not work. I do not have any of this -- so I am going to start out with the tried and true -- Lil'Gun. With the bullet seated, the case capacity for Lil'Gun is approximatly 34 grains. My goal is a minumum velocity of 1800 fps in a 16" barrel (duplicate a 45-70 load out of a 18.5 inch barrel). My starting load will be 28 grs, using wsr primers and I will work up from there. I am going to stop on the first go around at 32 grs.
Another powder to try would be V V 120.
For those of you that have "quick load" The bearing surface of the bullet is 0.5 inches. The case capacity of water with bullet seated is 35.8 grs of H2O. Set the max operating pressure at 40K.