Neck not hollding the 300rum bullets

[Yoteklr]

They need to be annealed.

 

[badaxeriverman]

I annealed a couple of them to the point where they were so soft the case necks crushed when I seated a bullet in them. I figured they were springing back after I initially annealed them. Nope wasn’t the issue. I’m guessing that the neck wall thickness is too thin from several firings and full length sizings.

 

[RL338]

Measure a loaded round minus .308” then divide by 2 should give you the neck thickness.

 

[badaxeriverman]

Thanks it’s been a few years since it happened, but I’m pretty sure I did that and it was pretty thin versus a brand new case.

 

[Yoteklr]

I annealed a couple of them to the point where they were so soft the case necks crushed when I seated a bullet in them. I figured they were springing back after I initially annealed them. Nope wasn’t the issue. I’m guessing that the neck wall thickness is too thin from several firings and full length sizings.

You need to clean the sticky tarnish off the case from the annealing. I tumble in corncob.

 

[badaxeriverman]

I pin tumbled them. It works better than corn cob media. They’re polished inside and out and even in the primer holes. Made zero difference. The brass necks imo have stretched so many times that they are too thin and are not getting sized down.

 

[grry10]

From all that has been shared, we know that you are not getting enough neck tension. When I load I want a minimum of .002" - .003" neck tension, some like .004". What are your actual mic'd neck measurements, fired, FL or neck sized, and loaded?

 

[badaxeriverman]

I’ll have to pull some of those out and try and full length size them like it’s a fired piece of brass and then try and load a bullet in them and measure and report back. I think I ran into those casings the other day. I think there’s only 7 to 12 of them left. I can remember when I go to seat a projectile I can feel it seat with force. Once the bullet is seated there is zero spring back for neck tension to hold a bullet in place. It’s basically once the bullet is seated in place it expands the neck and there is zero spring back on the neck tension. Like I said, I’ve had it with random 243 cases that have been shot dozens of times and probably should’ve been discarded way before the fact but I’ve never had it with 300 rum brass all in a row like I did a few seasons ago loading for it. It was a brass I had laying around since 99 or 2000 that had been shot probably a half dozen times or ALOT more. And I believe I posted above that RCBS sent me another expander ball to try and it made zero difference.

 

[grry10]

When it comes to neck tension, it should not make a difference if a case is just neck sized or FL sized as long as both dies size the necks the same. I'm guessing that if it is that old of brass, when you're sizing it the brass it is not staying to the proper size and is springing back some. I don't believe that there is any issue with the dies as long as you have them properly adjusted. My only suggestion is to properly anneal your cases and then size. That should soften the necks again and reduce the spring back, which is due to trying to size hard brass.