Case head seperation?

[gunrack]

I had to trash several pieces of brass today due to bulges in the brass near the case head. I had shot and reloaded the brass several times and never noticed any pressure signs on the primer or case head before. I checked all the specs on the brass and all are good just starting to see a bulge about a half inch from the case head.

I have shot max loads and slightly over before but took care looking for over pressure signs at the time. I am not sure because I am not shooting on or close to the max charge for the round.

Reckon the case life has been reached or I am not shooting the correct propellant? Shooting a .243 and using 40.5 grains of IMR4350. Not seating to the lands. Seated .025" off.

Looking for some kind of feedback ideas of potential causes.

Thanks

[s3silver]

Powder, charge, and COL seems right. I'd say double check headspace. If that's good then case life might be at an end.

FWIW, I've shot slightly over max in my AR 6.5 Grendel for a long time (12+ reloads per case) before I saw what you're seeing. The case had the same separation you're describing. This was with Hornady brass.

What brass are you using and how many reloads before separation?

[gunrack]

I have been checking the headspace. According to SAAMI specs they check out good. All of these are Winchester brass and they have been shot eight times. I only full length size as they become harder to chamber. I usually just neck size until the rounds become hard to close then I full length size again.

Thanks for your reply. I know very few folks that reload rifle ammo and it's really nice to have this knowledge base to ask for help.

[243LPR]

If it's a factory chamber it could be a hair oversized working the brass too much. I think if you get 8 loads out of a Winchester case you're doing good. Save up and buy yourself some Lapua.

[gunrack]

If it's a factory chamber it could be a hair oversized working the brass too much. I think if you get 8 loads out of a Winchester case you're doing good. Save up and buy yourself some Lapua.

It is a factory chamber. I have never measured it so it sure could be. It's a savage 110, I don't know if that is typical or not for them to run oversized or real close?

I just ordered 100 pieces of Lapua the other day. They should be here tomorrow.

Thank you

[Texas10]

It doesn't sound to me like you are describing case separation, but normal case expansion just above the case web, the thicker portion of the case. You can check this by sectioning a couple of cases lengthwise and look at the wall of the case. Look for a drastic thinning just above the web.

Since you are not FL sizing your brass every time, but only as necessary to get it to chamber, you are not working your brass very much. Your load is not particularly hot, and case life should be very good. I have several hundred cases of mixed mfg that have gone through this model 11, some reputed to be very soft, and the only issue I've found is loose primer pockets in some.

I'm loading a little hotter load in my 243 and yes, the brass shows some expansion like yours, but everything is safely within limits. Brass is not growing, and unless it's growing, there's no way the brass is thinning out and close to separation as there's no evidence the brass is "flowing".

I run Lapua in my 22-250 and also just neck size as much as possible, but also set my FL die to bump the shoulder back .001 when necessary to chamber. I'm getting 4 to 5 loads before FL sizing.

You should get very good life out of your brass when working it as little as possible. Primer pocket looseness, not case separation will probably be the reason you will have to toss any. Annealing your brass is a good way to extend case life too.

[s3silver]

Usually you can tell if the chamber is slightly oversized. During full length sizing brass fired from oversized chambers will take more effort to size. You can also take a bunch of range brass, measure towards the case head, then measure your brass. This should give you an idea how loose or tight your chamber is.

For example, the brass (using Federal for now) fired from my LR308 without any sizing will chamber into my Axis without issue. Brass fired in my Axis will not chamber in my LR308. Axis has a loose chamber and LR308 had a tighter chamber.

Some brass just doesn't hold up very well, but I am surprised your Winchester brass is giving out. I'm using Winchester brass for my 284 Win and I have around 10 loadings with no issues yet. On a side note, I had a few hundred 308 brass, headstamped SBS, that were exhibiting loose primer pockets only after the 3rd firing, hence now using Federals. You will be happy with the Lapua brass. Let us know how they work out for you.

[Robinhood]

If it's a factory chamber it could be a hair oversized working the brass too much.

:cool::becky::first: in combination with the reloader over resizing the brass. Are you getting carbon on the case body?

[bigedp51]

http://www.milsurps.com/images/imported/2009/03/308fail-1.jpg

http://www.milsurps.com/images/imported/2009/03/308fail2-1.jpg

[gunrack]

No just a little on the neck.

[gunrack]

That's exactly the same point as the shinny bulged line on my brass but no separation in mine yet. I tossed them before they reached that point.

[bigedp51]

Below are two British .303 cases fired in the same Enfield rifle. The case on the left is larger in diameter and has .010 thicker case walls in the base. The case on the right is smaller in diameter and expanded more to contact the chamber walls. Neither case stretched or thinned in the base web area when fired, and shows that a smaller diameter cases looks worse when fired but the expansion ring means little.

http://i122.photobucket.com/albums/o254/bigedp51/privihxp-1_zpsshjfudwg.jpg

Below on the far left a new unfired Remington .303 British case. In the center a once fired case and on the right a case fired and full length resized four times. This case expanded but cracked and started to separate and my point being radial base expansion does not mean the case is about to separate. The actual stretching and thinning happened above the radial base expansion.

http://www.milsurps.com/images/imported/2009/06/shouldera-1.jpg

Below same case at a different angle.

http://www.milsurps.com/images/imported/2009/06/IMGP5191-1.jpg

Below my RCBS case mastering gauge set up to check for thinning in the base web area. (a $100.00 fancy bent paper clip)

http://www.milsurps.com/images/imported/2009/06/IMGP5203-1.jpg

[Robinhood]

Nice job Ed.

[243LPR]

303 Brit is notorious for stretching cases. I've had to dig more than one case out of a chamber after the head broke off.

[s3silver]

http://www.milsurps.com/images/imported/2009/03/308fail-1.jpg

http://www.milsurps.com/images/imported/2009/03/308fail2-1.jpg


Wow, very surprised the Remington brass beat out the Lapua! Did not expect Norma to be so good either.

[s3silver]

http://www.milsurps.com/images/imported/2009/03/308fail-1.jpg

http://www.milsurps.com/images/imported/2009/03/308fail2-1.jpg



Is there an article for this study? Link anyone?

[bigedp51]

Is there an article for this study? Link anyone?

I think it came from Handloader magazine, the ammunition was fired in a new Savage .308 rifle. It didn't state what the actual rifles headspace was or if the press was setup for minimum shoulder bump.

[bigedp51]

303 Brit is notorious for stretching cases. I've had to dig more than one case out of a chamber after the head broke off.

With a rim thickness of .058 and at maximum military headspace of .074 you will have .016 head clearance or airspace between the rear of the case and the bolt face.

http://www.milsurps.com/images/imported/2009/08/headspacestretch1-1.gif

A trick I learned from the Canadians is to slip a small thin rubber o-ring around the case to hold the case against the bolt face to fire form the cases.

http://www.milsurps.com/images/imported/2010/02/headspacestretch_frame_0001-1.jpg

After fire forming you neck size only and let the case headspace on it shoulder.

http://www.milsurps.com/images/imported/2010/02/fireformedzeroheadspace-1.jpg

The problem is the military chamber is larger in diameter and longer to the chambers shoulder than commercial SAAMI standards. Meaning the full length resizing dies are much smaller than the chamber and overwork the brass.

[LongRange]

It didn't state what the actual rifles headspace was or if the press was setup for minimum shoulder bump.

exactly so how can anyone come to a realistic conclusion about FL sizing with no actual info about the test other than brand A failed xx brand B failed xx.
now im not arguing FL sizing VS neck sizing because its a waste of time...i say do what works for the person doing the loading...but i am hear to say that i have had 28 loads on 260 lapua brass that still had decent primer pockets when i tossed them...ive also tossed brand new 260 lapua in the trash after the first firing...the difference was 400FPS with the same bullet....ive also had 17 loads on nosler brass in a 300wm with 210g smks at 2900+ fps....with 13-15 loads been the norm.

now i agree if your bumping the shoulder back .005+ every time you FL size then you are definitely over working the brass and contributing to short case life BUT pressure is the biggest killer of brass not FL sizing...if the FL sizing die is set up correctly...again im not arguing which way is better just pointing a few things out because i FL size every time and have been for about 7yrs now.

[gunrack]

After reading all the replies and thinking about it I decided to do a little measuring to see if I could find anything abnormal. I pulled the firing pin from the bolt of 2 rifles so that there could be no tension on the case as it was chambered. I took a bunch of fired brass and picked through them until I found a case that would not allow the bolt to close or drop easily as it was closed. Measured all of the cartridge dimensions and wrote the measurements down. I looked though all of the material that I could find and in both cases the headspace spec was considerably different that what I measured with a comparator. The .223 would not chamber a fired case with a headspace of 1.461 but the spec says 1.467. The .243 that I measured which was the reason for this post initially measured out that 1.625" would not chamber. I set both full size dies up and started adjusting them a little at a time until I was able to bump the shoulder back enough for the bolts to drop with ease. I measured the change in head space after every cycle of the die and settled on a shoulder bump of .003" for both rifles.

I would not think there would be that much difference between the published SAAMI spec and these rifles chambers unless it is just the difference in my gages and/or methods of measurement.

Thoughts?