Hi David - I've not heard of any of the guys having problems, and they'd show up here if they did. The only trouble I'd think, might be from stock wood not taking the recoil. The pressure developed is still very mild, compared to small calibre BP rifles. I would be surprised to see a pressure figure of over 12,000PSI for a double 12 and that might take 250gr. or more of 2F to do that - shooting round balls, that is.
: My old double 12 made in about 1900, maybe before & stamped with "Fluid Steel Barrels", is still going strong. The guy who owns it is still shooting black powder ball loads for moose, although that's frowned upon here in BC. Apparently the game branch doesn't feel they're powerful enough. Bloody idiots. With no vents or nipples to let out some pressure, his loads of 5.5 drams 2f would equate closely with 175gr. in a muzzleloader - likely, just a guess. I shot a lot of 191gr. loads (7 drams) with round ball and they showed no more pressure than typical modern shot loads - so, perhaps about 10,000 to 11,000 - maybe. Hard to say, I don't have any pressure equipment.
; A number of the guys with the Pedersoli's have returned them due to problems with locks and cross firing and have been given new ones. One guy has tested and returned 2 that crossed with piddling little loads but was 3rd time lucky.