Home Forums Hunting & Shooting Ask The Gunwriters Gas venting and modern bolt actions

Details please.

These posts scare me. For decades I had assumed that the pre'64 Model 70--the rifleman's rifle--was the pinnacle of bolt actions except maybe for the Weatherby MkV. The only one I have left is a .375 which I load under maximum., With a magnum like that you don't need the last fps of velocity.

I had a batch of 6XC (formed from resizing and fire forming 22-250 cases) that I reloaded 30 times, trying to see how long cases lasted. The load was (calculated at) only 42,000 psi. I thought the failure would be loose primer pockets or split necks. It never occured to me it might be case separation.

The only problem I have ever experienced was with a Savage model 99 in 308. I had just gotten the rifle and was shooting some handloads the previous owner had loaded up. When I ejected the first round, only the case head came out. It was completely separated from the rest of the case. I didnt feel anything out of the ordinary when I fired that round. No gas nothing??

Anyone have an opinion on the Montana rifles safety/ability to handle gas? I've read they are more like the 98 than the model 70 but am not sure how true that is.

Good thread, I did not know that Savages were that strong. I've always liked them.

If you only neck size there's really no reason to have a case head separate. Ditto if you partially size such that the shoulder isn't pushed back, and holds the casehead against the breechface.

Where you see case head separations is where there's clearance between the breechface and casehead, such as where a bottlenecked round has the shoulder pushed back each time the case is reloaded. What happens on firing is that the firing pin drives the case forward, and then the case expands in the chamber to seal and grip the chamber walls, while the thicker head section doesn't expand but instead gets pushed back to meet the breechface. If there's enough room the brass will yeld and you get plastic (permanent) deformation. You thus get a very localised area at about the point where the thicker casehead meets the thin part of the case. about 1/2" or so from the case head, where the plastic deformation occurs - and you can often see it if you look. Each time you push the shoulder back and fire it again, this area gets stretched again, causing it to become thinner and harder, until the case separates at this point. You will also see it in rimmed cases or belted, where there's too much headspace.

You can avoid it by necksizing only, to ensure that the case is more or less against the breechface on firing, such that there's no room for it to stretch enough to yield. Alternatively you could check inside each case for the localised necking of the material with a bent wire, but IMHO it is better to avoid the problem. I've had batches of brass go well past 30 load cycles since I worked this out a fair while back. The main determinants of case life for me are losing them in the field and neglecting to anneal necks and having them split. Sometimes I also have primer pockets get a bit loose after a while.

FWIW this case head separation is a different thing from a case head failure, which is where the case head itself ruptures, such as due to a material defect (which would be pretty rare) or overload/pressure excursion. The case-head separations I've experienced have never been particularly dramatic, and often I only noticed when I couldn't chamber another round.

After living for 34 years in one house we moved. At the new location my reloading press and powder scale had to be mounted differently than previously. I had been wanting to make up some light 40 gr. loads using a fast burning powder. The new angle of the powder from where I sit resulted in an incorrect setting on the scale. My fault I didn't check closely enough to avoid the error. I don't try to blame others for a failure on my part.

Jim

Most Savage 99,s I have loaded for have large chambers I keep the brass, dies, separate, and don't load past med or lo book loads. 250-3000 and other long sloping cases in a 99 you have a lot of case stretch. So I watch the case to prevent case failures.

A modern bolt action, you may want to consider is the Steyr SBS Pro. It is a 6 lug fat bolt design with a SAKOish type extractor. How does it compare safety wise? Dunno since I've no experience with gas coming back at me while shooting it. I don't know if I shouldn't be impressed when Steyr claims proof to 120K PSI, so I am. If you do a search, you will find that it has more than a few positive features not the least of which is how well it shoots. My Steyr SBS in .30-06 is easily the most consistently accurate factory rifle in my gun safe. Not always 1/2 MOA but often enough to think that it could be.