Arggh. I can't get on at Accurate Reloading. Been a long time, I had to re-register and am not yet approved to post.
They go into a lot of foo-fraw about action strength that I do not think is a real worry. In the first place, a good shotgun does not carry all the load on the hinge pin like a H&R single shot. It has locking lugs that drop into recesses in the action. You never notice because they swing into place along an arc and are stressed lengthwise. In the second place, a 20 ga shotshell has over twice the casehead area of a .45-70 so even a top .45-70 SAAMI load is not treading very hard on the safety margin, when figured as force against the breechface. A lot of study goes into locking bolts, what Greener called "holding down bolts" but the load on them is not really very great. Greener said that one of his guns could be fired with the bolts removed, the action held shut with "a turn of common cord."
Greener attached a lot of importance to his crossbolt extension. Gough Thomas said it did not add a whole lot, and HE was a mechanical engineer.
