Ok, I just got off the phone with Gordon, he stated that the older late 80's to possibly the early to mid 90's frames aren't as strong as modern frames, but wasn't sure when the strength improvements were made, apparently changes in strength were made in steps over the years, but he had no year of manufacture that he could definitely say when the heat treating and strength was improved. Other changes that occurred over the years were manufacturing tolerances, which brings us to the 45 Colt which is supposed to have an asterisk on it due to the fact that
all new chambering offerings will only be fitted to '992000 and later frames, regardless if they're high pressure or not, the misfire issues lendar mentioned would be due to the tolerances and changes in specs of current barrels that aren't compatible with pre '99 frames, not that they've had misfire issues, just that they could due to the differences.
He also stated that a defective barrel and/or frame made 1987 or later would be replaced, as in lendar's case, a 243 barrel with a 243 barrel., but that any other chambering, even tho a high pressure offering, would not be fitted as an accessory barrel. Considering the stated warranty on an H&R is 2 years, that's still a very generous unwritten policy!!
I asked specifically about shooting factory ammo in pre '99 high pressure chamberings such as the '96 RMEF 35 Whelen, and he stated they are perfectly safe to do so,
reading between the lines here and offering an opinion, I believe that to mean safe in that there will be no catasrophic failure, but due to the fact that we know actions will loosen up over time on some high pressure chamberings, the older frames, particularly the oldest of the double prefix serial numbered frames, may not hold up to those chambering as well as a modern frame.
Thanks to lendar, Mac and Gordon, maybe the muddy water has been cleared up a little since all that has been stated is true to a degree, it's just not exactly cut and dried as to when it's true!!
Tim