As some of you may be aware, I have somewhat committed to standardizing on the 357 magnum case for most of my guns. YMMV, but it seems to do everything I need a gun to do (except fit 8+ rounds in a J-frame, but I digress...).
One of the things I haven't ever been able to put my hands on is those darned expensive .38 caliber shot capsules made by Speer or whoever it is, so I thought I would look into printing some to play with. I disassembled one of the 20ga target cartridges for my wife's O/U (shhhh, don't tell her) and that yielded 7/8 ounce of #9 lead shot, so that's what I have to play with.
I was trying to determine what kind of load weight might make the shotshell in 357 a bit more effective (we have some real pressure headroom to play with if desired...) and I settled on the 1/2 ounce I noted from a 410 target load. 410 isn't a powerhouse, but sure is better than shaking a stick. The gun this is intended for is a T/C Encore with a 12" barrel and a 357magnum chamber, although it should work in any single-shot gun that chambers 358 projectiles. I printed a prototype capsule which has an overall length of 32mm (just over 1-1/4") and two diameters: 0.359" for the part which seats in the case and 0.347" for the part which extends into the bore. Right now, the current design has 17.3mm (0.68") of length which extends outside the case and it holds 130gr (0.297 ounces) of #9 shot. I need 0.203 ounces (88.8gr) more to reach an even 1/2oz. load, so call it an additional 70% volume. That would put the overall capsule length at 54.4mm or 2.14". That's 39.7mm (1.56") protruding from the case.
Bearing in mind that I have no experience with this kind of device, I don't see anything immediately obvious which would cause problems having the capsule project that far into the bore. Are there any issues I should keep in mind as I move forward with my experimenting?