I have played with this a little bit.
I feel the determining factor to some degree is the quality of the thread fit. WHen you accurize a receiver, you recut the threads using a one half of a matched set of thread cutters. One does the internal receiver threads, the other does the barrel threads.
Using these matched sets of thread cutters, you can get a thread fit that is amazingly quality. When your machining the threads, you can have the threads be to tight to start the barrel and then, just by taking a 1 thou cut(1/2 thou but off both sides 1 thou total cut) and the receiver will thread on all the way to the barrel shoulder.
With a thread quality like this, the amount you torque the barrel to is much less important.
Many 100 and 200 yard BR shooters have their barrels torque on very ligthly, in fact I have testes a 6mm BR barrel that was torqued to only 20 ft/lbs and it shot AMAZINGLY well and did so for well over 300 rounds.
On the other end of the scale, I have tried this with my 7mm AM and the 200 gr ULD RBBT loaded to 3300 fps. The barrel was a 30" #7 contour Lilja with a 1-7 twist. I indexed the barrel and lug so that I could tell if the barrel turned at all. After four firings the barrel did start to turn simply from the torque generated by this extreme round, heavy bullet and fast twist.
I do not use a torque wrench anymore either, just go by feel. I would guess it would be around 70 to 80 ft/lbs on my larger rifles that will produce alot of barrel torque. I would say its pretty much the same for the smaller ones as well as they are all pretty much the same.
What is needed to keep a barrel in one place, on a factory rifle, I would say they would need more because of the poor thread fit. Some factory barrels are put on with well over 150 ft/lbs of torque which is not needed in any way. Other are screwed on with thread locker as well to hold them in place.
The varation in barrel torque from one factory rifle to another is frankly amazing to me. One barrel will pretty much fall off while another one I will need my 6 foot cheater bar to break it loose. May be a big reason that factory rifles are so inconsistant from one to another.
I would say anything over 60 ft/lbs with a factory chambering would keep a barrel in one place pretty easy but 70-80 would be better in my opinion. I would doubt I ever get near 100 ft/lbs.
Kirby Allen(50)
