[ngashooter]

I got out to test some more loads through the .264 Win Mag this morning. The first three test loads had fed, fired , and ejected fine but accuracy was less than stellar. I had hoped I could get to book max as listed by Hornady. They published 66.1 gr of Ramshot Magnum as maximum with their 140gr SST bullet. I had loads of 65.8gr and 66.1gr with me today. The 65.8gr load shot into 2 inches without any issues. I shot other guns while the barrel cooled. The first shot with the 66.1gr load resulted in difficult bolt lift. Yanking it up and back ejected a case with obvious problems. The case had partial head separation with a crack about half way around the circumference in front of the belt. I did not attempt to fire any more of those. I will pull the bullets and recycle the components. I will stay with the 65.8gr charge as it has good power

and acceptable accuracy for my needs.

 

[ngashooter]

Now I don't reload for rifle but did you notice anything in the "feel" when you pulled the trigger? Do you think it was the charge or maybe a bad piece of brass?

The case was on its 2nd reload. It was a Winchester case from a Super X factory load. Its first reload was a mild charge of Ramshot Magnum as i began to work up a load. The case was full length resized, trimmed to length, and cleaned prior to being primed with a handheld tool. It was handled and inspected frequently. Nothing was visible from the outside. The charge was weighed individually on my Lyman scale. I was throwing charges a little light from my Redding powder measure and using a trickler to come up to full weight. There could have been an internal flaw, but I wasn't going to shoot any more to find out if it would destroy other cases. The 98% load is fine with me.

 

[ngashooter]

Just for kicks I'd get a paper clip and fashion up a head separation tool. Normally when a case is getting ready to separate you will see a white line on the outside of the brass near the base. I don't see any evidence of such on your other brass that did not separate.

Bend a paper clip into a sharp bend and then sharpen the end on a knife stone. You can then reach down inside the case and run the sharpened end up the inside from the bottom. Scraping the inside of the case.. If you are developing a separation the sharp paper clip will catch the ridge.

No disrespect if you already know this info. Trying to help.
Bepe

I will certainly be doing this. I have made the little tool in the past, but will need to make a longer one for the magnum rifle brass. After i pull down the remaining rounds I will be inspecting those cases very carefully. I will use that tool as well as a digital bore camera to look inside.

 

[ngashooter]

I was going to suggest what @Bepe said. I suspect it’s just a single case. But just for fun, have you measured your cases at the shoulder before and after sizing to see how much you are working the brass?

I have not, but can see the purchase of a new tool the horizon.

 

[ngashooter]

I will order the Hornady gauge. Since I have no history on the rifle except what I have found online it's possible it was an art project. My thought is that a gunsmith known for making bench-rest rifles wouldn't sign his name on anything shoddily assembled. Just the time spent jeweling the bolt shows he cared enough that I doubt he was negligent setting headspace. The Hornady page with load data for this cartridge had a specific warning of over pressure signs appearing suddenly.

 

[ngashooter]

I only own one rifle that uses a belted case, a 30-338 (which, other than neck diameter is the same case as your .264), single shot Mauser action gun built for 1,000 yard prone shooting decades ago so only have a little practical experience with them. From much that I have read, the belt was originally intended to prevent cartridges like the .300 H&H from having ignition issues because they did not have much of a shoulder to position the primer consistently against the bolt face. Belts then came to represent a symbol of a 'high power' cartridge so they were put on any round that the manufacturers wanted to 'hype', whether it really helped anything or not. The .264 has plenty of shoulder and doesn't 'need' a belt but, it got one anyway. If your .264 Mag seems to function fine with factory ammo you may not really have a rifle headspace issue but your sizing die could be short enough that you end up bumping the shoulder back and creating an ammo headspace issue. After checking your brass to insure that there isn't a really thin section right ahead of the belt (no point in tempting fate with more head separations) try turning your sizing die out a turn. Then work in slowly from there until the cases fit and you can close the bolt on the case with just a little effort.That will keep the shoulder where it fits your rifle and should prevent the problem.
That at least worked in my Wimbledon gun, I lost a number of cases to neck splits because I didn't know much about annealing 30 years ago but never had any head separations.

Bruce

Excellent advice! Thank you.