Hello again.

Cross posted in reloading.

I just got my RMC custom brass.
20 Ga 3" long.
Two wall thicknesses one for 0.625" ball and one for 0.622" bullets.
H2O capacities 195.6 Ball and 193.8 Bullet.
Ball and bullets will have 0.002" tension fit.
CCI 209 Magnum primers.
Ball 0.625" 350grain hard cast lead.
Bullet1 0.622" SWC 0.625" long, 3 bands 0.110" each, 2 grooves. 450 grain.
Bullet2 0.622" RN 1.030" long, 2 bands 0.110" each, l groove, crimp croove. 720 grain pure lead.
Bullet3 same as 2 either HP 3/8" drill bit, 550 grains or base drilled "conical" to 550 grain.

Accurate Balistician thinks that A5744 will not have enough pressure to burn well.
Suggested Trailboss.
Called IMR. Head guy "Ron" suggested 70% rule.

Case holds 63 grains to rim, 48 grains to base of SWC Bullet.
70% 0f 48 is 33.6 grains.
QL says MAX is 29.4 at 12,500 psi.

Any thoughts or suggestions.
Need sanity check, before pulling trigger.

Thanks guy's

Nitro