Hey Bruce nice picks and glad to hear someone is tearing them up.
I think in continuation of the discussion where you were enlightening me with the TPS info, we were trying to just to get recoil comparisons to what is actually happen. Btw those charts are awesome. I have another brand sxs 28 gauge that is my brush gun and those choke killing diameter charts you have are helpful.
My point was that just the way sxs guns are made, if you get above 16 gauge the cumulative or maybe one time of too heavy a load can create stock issues on older Parkers and maybe even all older guns using more brittle American walnut. Say if you have a 1 Frame 16 gauge and a 1 frame 12 gauge, inherent with 12 gauge loads your recoil pounds go up and hence you can just have more wear tear issues on the same sized stock. Again almost every field grade 12 gauge Parker I have seen littered across gun shops have some issues with stocks. 16's obviously can if you get loads approaching 12 gauge. I think most 12 gauges are in the 1 1/2 frame but..
I was putting say the same dram equivalent of black powder to grains and coming up with some pretty high numbers in the calculators. The calculators require a grains used of powder. A box of shotgun shells, if you can find them will say dram equivalent. But more and more they don't even say that, they just put a velocity number. I think the calculators are thinking you are using the modern powder grains instead of black powder grains and it produces maybe conflicting results.
BTW Heff, Bruce referenced this chart below from another thread where he was talking about a 16 gauge loads as recommended by Parker. Slide your eyes down and 20 gauge info is there as well.
