I am going to have a Persian Mauser barrel rechambered to 8x68S, then cut and crown to 26" and turn the steps out.

I have had problems with K98 barrels "walking" after turning because of stress.

The Persian barrel will let me keep more meat on the barrel, so that will help some.

Since simple "cryo" treatment is so reasonable, I think that it would be cheap insurance.

Would it be best to treat before turning, after turning or both.

I here it makes machining much easier when done before, and treating after would relieve any new stress imparted by machining.

Cryogenics WILL NOT RELIEVE STRESS.If you look up stress relieving treatment in a metallurgy book you will see something like -heating to 700-1100F will relieve stress.You should start out by first heating the barrel to relieve stress, then machining .If machining is then done carefully that's all that will be necessary. Poor machining will require stress relieving treatment afterward also.

I am not sure what to tell you about cryo and an already rifled military barrel. I suspect the quality of the existing rifling will be by far the most important factor.

Having said all that, a few years ago I had a LONG chat with John Kreiger at the S.H.O.T. Show about the benfits/downsides of cryo treatment before RIFLING. He told me he does it because it reduces his wastage by a factor of something like 8 times.

So, for very precision barrels, it may well be worth while, whether it reduces inherent stress or not.

Don't think, personally, I would spring for it on an already rifled military barrel, though.

Good luck, whichever way you go.

Alberta Canuck