Split necks.

[LHSmith]

Bad lot of brass.

 

[savagedasher]

My bushing all are smaller inside then the number on them. That is done for a reason.
When sizing you must have a smaller hole . All because of the resistance of compression. Lube will make the hole smaller also. The spring back after seizing is always very with hardness. A .265 bushing doesn't always give you a neck of .265 .
My advice is to check the inside diameter of your bushing then check the finished neck.
My non bushing die I had ground the cases vary as much a .0005 all because of the hardness of the brass..
Larry

 

[jlow]

Larry – everything you say make sense but I can tell you from personal experience measuring many bushing that the degree of under sizing varies considerably from 1 thousands to 0.4 thousands and everything in between.

The point is if the under sizing was intentional, one would expect the degree to be consistent, but they are not. In the end, you could still be right and they cannot control it to the degree that we would like but the difficulty is you don’t know what you are going to get when you buy a specific size bushing, even if they are the “same” – yes, I have measured different bushing of the “same size” but they are in fact different.

In the end 1 to 0.4 thousand does not seem much as a number but when you are trying to get 2 thousands neck tension from the bushing, you can be 20% to 50% off....

 

[Webster]

There are endless discussions on sizing and annealing but one thing is never talked about. It could only be researched in a lab with special equipment. That’s strain rate. If you stretch a piece of brass of some length slowly and stretch a piece rapidly they work harden differently.

If a case neck is blown out to the chamber walls at 58K PSI and another one at 70K PSI the rate of strain should be different. I don’t know but does this mean if your load produces 70K PSI is it stretched so much faster that it work hardens beyond what we normally see (the speed of stretching)? We may never know the answer to this. If it isn’t reasonable to anneal longer or a higher temp try annealing twice with cooling in between. 750F is the very bottom of the annealing range. If you are heating for about 8 sec you are probably in the 750-850F annealing temp range for about 1-2 seconds. You don’t get much anneal in two seconds.

I wouldn’t think a custom action is safe at 70K PSI. Enlarged primer pockets are a sign of very high pressure even if you don’t see other signs. If you are reloading for someone else you can be sued if they are injured by your reloads.

 

[Ledd Slinger]

Hey do you fellas remember firing factory 303 British ammo in the old military rifles? Those cases split on a fairly common basis after the first firing. Granted the 303 brass is pretty thin, but I remember finding that the cause was largely due to excessive headspace coupled with hot factory loads.

Once i reloaded the once fired brass (the pieces that survived) with proper headspace, they seemed to hold up fine.

I'll have to read back and make sure headspace wasnt already covered, but do you fellas think that could be a possible cause of the issue?

 

[jlow]

I think it is impossible to give an answer to work hardening due to 58K PSI vs. 70K PSI but at least to me, the degree of difference to produce neck splitting after one firing seems excessive.

I have never heard headspace problem being the cause of neck splitting, case head separation for sure.

 

[Ledd Slinger]

I have never heard headspace problem being the cause of neck splitting, case head separation for sure.

Yeah Hornet brass can do the same thing when forming an Ackley shoulder with a hot load. Of course a 338 Ultra and 22 Hornet is apples and oranges and 22 Hornet brass is also very thin like 303 British.

However, going off of the previous post, if we are to assume that strain increases on brass as pressure increases, i think it is reasonable to factor in the distance of movement under said pressure as an additive to the weakening process of the brass. So i think a combination of a "hot" load with excessive headspace would compile the problem.

 

[Sheldon N]

Yeah Hornet brass can do the same thing when forming an Ackley shoulder with a hot load.

I've had case neck splitting on 280AI fireforming with Remington brass and a hot load.

 

[Ledd Slinger]

Granted this is all most likely a bad lot of brass from the factory as others have stated, but i would be curious to know the neck wall thickness of the problem brass vs the brass that lasted 7 firings with no split necks. If the OP has a Redding concentricity gauge or similar tool available, it would be a quick and easy check.

I understand that the neck wall thickness can be determined by subtracting outside neck diameter of a loaded round with the diameter of a bullet. The reason for this is because it may identify thin spots in the necks. Cant remember what type of brass he is using, but Remington brass is notorious for having necks that are much thinner on one side

 

[savagedasher]

There are endless discussions on sizing and annealing but one thing is never talked about. It could only be researched in a lab with special equipment. That’s strain rate. If you stretch a piece of brass of some length slowly and stretch a piece rapidly they work harden differently.

If a case neck is blown out to the chamber walls at 58K PSI and another one at 70K PSI the rate of strain should be different. I don’t know but does this mean if your load produces 70K PSI is it stretched so much faster that it work hardens beyond what we normally see (the speed of stretching)? We may never know the answer to this. If it isn’t reasonable to anneal longer or a higher temp try annealing twice with cooling in between. 750F is the very bottom of the annealing range. If you are heating for about 8 sec you are probably in the 750-850F annealing temp range for about 1-2 seconds. You don’t get much anneal in two seconds.

I wouldn’t think a custom action is safe at 70K PSI. Enlarged primer pockets are a sign of very high pressure even if you don’t see other signs. If you are reloading for someone else you can be sued if they are injured by your reloads.

Rate and amount are totally different . The difference 58 to 70000 PSI could if any make the case thinner.
If 800F is the temperature needed to anneal that could be attained in far less then a second. Time is only relative to how and what is making the heat. Induction heating the time could be very small amount.
Just a gas change in the tips you have changes the time it takes. Larry

 

[4xforfun]

I wouldn’t think a custom action is safe at 70K PSI. Enlarged primer pockets are a sign of very high pressure even if you don’t see other signs. If you are reloading for someone else you can be sued if they are injured by your reloads.

Where in the world did you come up with the enlarged primer pocket problem? Nowhere was it stated that the primer pockets were enlarged with this brass. Nowhere. At least not by me. I did state that after 7 firings in my own gun the primer pockets were starting to get a little loose on REMINGTON 300 RUM BRASS, but never with the Bertrom brass. Rum brass is notorious for week primer pockets. And, where did you come up with the 70K pressure??

 

[4xforfun]

Savageduster,

As far as the temps, you are correct. It does take more then 650 degrees to do the job. Since it is all I have, I use the 650/400 degree templaque on my initial testing of a new lot of brass. On a case the size of the RUM, the 650 Templaque melts almost an inch down from the body/shoulder juncture. I have no way of knowing for sure, but the temp at the neck has to be way north of 650 degrees, since this is where the point of the flame is hitting....right square in the middle of the neck. I use the 450 stuff down the bottom of the case to make damn sure I don't anneal the rest of the case. If the lower temp templaque on the bottom of the case does not melt, I am GTG.

Also, what were your thoughts on the whole neck clearance vs caliber thing I brought up? Did any of that make any sense to you? Is it plausable that .006 clearance on a bigger case is less of a problem than on a smaller case? The math that I come up with is that .006 clearence on a 338 caliber is like .004 on a 6mm.

Thanks again,
Tod

 

[dmoran]

Tod -

The fault in my opinion is the brass itself, nothing you did.
As to +006 clearance, that isn't diddly to most rifles ever made, and would be tighter clearance then many factory chambers.
I've run that much in a couple 6Dasher sets (never annealed) that lived as long as tighter sets and never split a neck.

When you get the replacement brass, try a few both ways, annealed and a few not annealed, and let us know back !.!.!

Good luck
Donovan

 

[Brians356]

If this is deemed the problem I can easily have Kiff re grind the reamer .002 less and set the chambers back. But, this would eliminate using Rem 300 Rum brass.

Not if you turn the necks.

 

[Brians356]

So now that we are back to square one, read this article. If you dont reach the right temp, then you are just wasting your time. But dont take it from me, below is a link to a good article on annealing. According to this article, using your 600 degree tempilaq isnt allowing the brass to get hot enough. He also mentions the dark room method of determining temp, which I know works. I'll never use tempilaq.

http://www.annealingmachines.com/how-to-anneal.html

I did read that article. He does not say "using 600-deg Tempilaq isn't allowing the neck to get hot enough", but he does say the neck needs to get to 650 for a fairly long period, or 750 for a few seconds, so if 600-deg Tempilaq is used inside the neck, your point is valid.

If the Tempilaq is used below the shoulder, about 3/8", and the 450 or 475-deg product, it will certainly assure that the neck is getting to 750. This was Hornady's procedure. You just want to be alerted that the body is starting to get very hot, and stop there.

 

[Brians356]

Also, what were your thoughts on the whole neck clearance vs caliber thing I brought up? Did any of that make any sense to you? Is it plausable that .006 clearance on a bigger case is less of a problem than on a smaller case? The math that I come up with is that .006 clearence on a 338 caliber is like .004 on a 6mm.

I did not notice any of your math calculations. As the original neck diameter gets larger, a .006" increase in diameter is causing less and less stretching of the brass. You need to calculate and compare circumference changes rather than diameter, as most of the stretching follows the circumference. Consider that as diameter increases, circumference increases 3.1416 (Ï€) times faster!

Of course a constant diameter change becomes less significant as nominal neck size increases. Illustrated with the extreme example, a neck 12 inches in diameter that increases only .006" suffers almost no stretching at all.