Jeff [JNW] says, "I think large shot weights and high velocity are much harder on old guns than moderate to high pressures."
And therein lies the conundrum, exactly what is 'moderate' from a pressure perspective? I'd personally have to say 7~8K psi in a 12ga. Go to the small gauges & I honestly don't know, but there are very few published loads for 20's that go below 9~10K psi. That makes RST a very valuable resource for those guns continued use.
High velocity and heavy charge weights both increase recoil and it's effect on old wood is cumulative and either can result in a stock failure. You'll get no argument from me on either of those counts.
OTOH, pressure is a factor too oft not understood w/people wanting to somehow factor it in with velocity which is wrong. Rather, it is a stressor that is independent of velocity whose effect is also cumulative and it affects weaker/older mild steels more so in terms of cyclic life than more modern alloyed steels w/higher pressure tolerance limits. Trying here to put it into layman's terms and likely failing at the effort, but high pressures in 'old guns' not designed for it nor made from materials that can withstand it are affected in the negative just as much as using heavy shot charges & high velocity loads even though the causal factors are not remotely related.
