There is a published loadHmmm, that is worrisome. I thought I was using CMwings' pressure tested load. He reported:
Reviewing your "ultimate load 12GA Waterfowl load" thread, your longshot load that failed the pressure test was:
3” cheddite hull
28 grains longshot
TUPRW123 wad
2 x 1/4” 20ga felt
273 gn tss under 273 gn steel
20ga OSC
fold crimp
1407 FPS, 15290 PSI
Is that correct?
CMwings can you weigh in here?
80611-370H in the cheddite manual
3 inch Cheddite hull and primer
31 LS powder
X12x
Tps41
OS12
9/8 steel shot
10600@1420
Your shot column at 50/50 tss/steel at 10/8 total weight is no longer than this one, but 1/8 heavier. I don’t see that building 5K psi, especially with a shorter wad. I’m not saying your data is bad, in fact I trust it over this published load for your build 100%. Just giving a point of reference. Fold crimps are the devil. I had a tested 10k 10 bore load come back at 18k because my fold crimps were too deep.