Bonanza,
Congratulations on both the fine gun and getting it to regulate. Thought I would just point out a caveat to your prior post above where you said you would just keep adding 4198 one grain at a time til it regulates.

The starting load of 65 gr. 4198 is 40.6% of 160 grains of B.P. (your 2 3/4" BPE's typical load), just what the doctor ordered according to Seyfried's "formula" for nitro-for-black loads using 4198 smokeless. I've seen Seyfried push on up a bit from 40% loadings; say, even 45-47%, but we should keep in mind there IS a limit, and smokeless loads can zoom up in pressure as grains are added - not a linear pressure situation at all. Not saying that is the case with 4198 used in this way, and certainly it is harder to build pressure in "large" bores compared to the typical modern one.

At 74 gr. you would have been loading 4198 at a ratio of .46 (46%) to the 160 gr. B.P. load. But since 68 grains gave regulation, that is a ratio of just .42.5 (42.5%), which is likely safe it seems to me - based on the considerable experience of others in using N-f-B loads of 4198.

Now if the 4198 load seemed to have stiff recoil, try your new baby with 160gr. of 2F Goex B.P.! OUCH. The recoil formula includes the powder weight as part of the projectile (ejecta) weight, so there is a lot more recoil with B.P. at identical velocities, both on paper and at the shoulder - from those who know. I have only used B.P. and only in a .500 X 3", so I shudder at the idea of B.P loads in the .577! Lots of people did, and do, shoot them tho.

Some recoil figures from a Table I have: .500 BPE with 136 gr. B.P. and 380 gr. bullet yields recoil of 63 ft. lbs. (about same as .458 Win. Mag.) Even with heavier 440 gr. bullet, the N-f-B load with 55 gr.(40%) smokeless has a recoil of just 42 ft. lbs. Quite a difference!

Now with the 2 3/4" .577 BPE using 160 gr. B.P. and 560 gr. bullet, recoil is a whopping 81 ft lbs. Even with stout smokeless load of 75 gr. smokeless (47%) and 570 gr. bullet it is 48 ft. lbs. Again, quite a difference!

Aloha, Ka'imiloa