Hello again.

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

You need to describe what you are loading.
Is this a 20 ga shot gun?
What sort of action?

Have you compared the data with traditional 20 ga shot shell powders?
How about comparing standard data with Blue Dot?

20 ga Double Rifle built on a 1956 Simson Suhl Anson Deely boxlock with Greener Cross bolt and side clips.
24" 1:24 barrels
That is why the 12,500 psi MAX.

I would just compare your data against proven 20 gauge data and see if it makes sense.

Compare to powders with the same burning rate for which there is published data. I would be inclined to start with a slow burning shotgun powder.