Thanks, Rich.
Miller, my post as written might be confusing to some, so for clarifiction my use of the term 'R scale' was in ref to 'Rockwell' rather than to any specific scale. If I read Rich's post correctly, he stated that the angle machined 'hard'. That would have much more to do with the 'feel' and be below the likely penetration of the case hardening, at least to my understanding of both machining language & case hardening. My understanding is that case hardening in excess of .010 inch penetration is both difficult and unlikely on the mild steels that were typically used for actions. And since this action is now sectioned it will be very easy to take a hardness reading below the case as well as through it in the area of the frame angle and in other places, like the main body or the water table. I think Rich's observation may shed a bit more light on why some of those small gauge Flues actions failed, aside from just being small, and thin in that area.
FWIW, my main bud often shot a 28ga. 1 & 1/2 grade Flues with normal modern loads, inclusive of a few 1oz nasty blasters, for 20+ years before selling it. I have no idea how many modern rounds went through it in that time frame, but numbers of flats anyway. It never showed any issues from the experience in spite of not being designed with modern ammunition in mind. Good practice? NO. Did it crack the frame or have other issues? NO. Perhaps it was not so 'hard' at the angle? I don't know.
To Jack's original question: I have seen SBT's that have been shot seemingly a jillion rounds and have never heard of one breaking a frame. Lotsa hoopla about them being much better after serial # 400K, but used to see plenty of the older versions w/#'s well below that at shoots where they were being used & still shooting. I suspect many got rebuilt like today's P-guns as they needed it &/or as parts wore or ultimately broke, but I have never heard of any frame issues. BT-99's in the early 70's allowed many to retire thier older I-guns and also the I -SBT's became quite collectable. They were never inexpensive. The last new that one I saw for sale was $1800 and that was, what?, close to 40 years ago, now.
