Here's a copy of a posting from several years ago of another forum that I saved. It's by Ed Harris, who I believe was the designer of the RCBS tooling and he describes the procedure for loading the 45 shotshell. A very interesting post. This is not all of it but what I required for my own use and this is the data I have used to make my own shot cartridges.
As with everything from the internet, double check everything before loading or shooting it. Use your own discretion.
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Form cases from 7.62 NATO or .308 Win. brass.
Charge with 6.2 grs. W-W231 or 4.5 grs. of 700-X
Insert Remington SP410 shot cup as used in 2-1/2" skeet loads, seat firmly against powder, positioning with 3/8 dowell and a few light raps with plastic hammer.
Trim wad fingers flush with case mouth using a sharp knife.
Use Lee #069 dipper to measure 110 grains of No. 9, 8 or 7-1/2 shot.
Slide 1/2 veterinary gelatin capsule open end down over shot, twist and push until worked down snug against the shot.
Alternately you can use a card wad cut with a 3/8 punch or a .35 cal. gasheck over the shot.
Adjust final crimp to a rounded shape which will feed.
The CCI-Speer .45 Shot Loads are a commercial version of this load, but do not use the plastic shot cup, and don't pattern as tightly.
The original handloaded versions would place over 70 percent of the pattern into a 15 inch circle at 25 feet, with an average of 10 shot in a 5 inch diameter circle at that range, individual pellet energy of 2.4 ft.lbs. and a pellet count of 125 No. 9 shot, which would reliably kill snakes, birds and monkeys at jungle ranges and would do as well for rabbits, etc.
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