When I last left this I had loaded up a tray of new .45 BPM cartridges with the intent on finding out if higher BP compression could increase performance. I ended up with a mixed bag. Here are the latest chrony results.
The performance of the 46 grain FFFg cartridge with 250 grain BigLube got a nice bump from higher compression. The velocity went up from 972 to 1014. It's only a 4% gain but it was nice to consistently be over the 1000 ft/sec mark.
I tried out a 48 grain version with the same bullet and also got nice results. 1032 ft/sec with the energy approaching 600 ft-lbs.
The performance of the 55 grain FFFg cartridge wtih 150 grain Biglube actually went down.
I guess there is a point when the powder has just been compressed too much. Did I squeeze all the oxygen out of the cartridge?
The drop was fairly significant IMHO. 1392 ft/sec (1/8" compression) down to 1232 ft/sec (3/8" compression)...an 11% drop! That extra 1/4" of compression really dumbed it down.
There really wasn't a change for the 60 grain FFFg loads. While I did manage to compress the powder more there really wasn't a whole lot more I could compress. With 60 grain FFFg you have to use a drop tube just to get it into the cartridge without it spilling out everywhere. By the time you compress the powder down for the bullet you've already compressed it pretty darn good.
I think I'll be as bold as to start to formulate some conclusions:
1. There isn't much to be gained with going over 55 grains of FFFg. 60 grains FFFg makes for a little more smoke-n-boom but there isn't a great performance increase with either the 141 roundball or 150 BigLube bullet.
2. 48 grains of FFFg and a 250 grain BigLube bullet makes for an excellent load. 591 ft/lbs energy
3. 52 grains of FFFg and a 200 grain BigLube bullet makes for an excellent load. 598 ft/lbs energy
4. 55 grains of FFFg and a 150 grain BigLube bullet makes for an excellent load. 577 ft/lbs energy
5. Roundball loads are not worthwhile as the 150 grain BigLube bullet gives similar performance and also provides for a lube groove whereas the roundball cartridge provides no lube. The roundball is also more difficult to load into a cartridge and potentially creates a concern that the ball will jar loose under recoil.
6. 60 grains loads are for the pure pleasure of making the most possible smoke-n-boom and freaking smokeless heathens out of their wits.
Once again, I did not observe any damage to the wedge or arbor of the Walker. I did however notice that every single daggum screw on the Walker was loose by the time I was done. :banghead: Even the trigger/bolt springs's screw was backing out.