First Case Head Separation

[Old Navy]

After many thousands of rounds I finally managed to separate a head from the case. ( 6BRX ) I wasn't too worried on the way home because I was sure the load was mild. (107 over 32.2 # 15) I studied my options and went with the easiest first. I pushed a .45 wire brush into the case until it partially exited the neck and pulled it right out. I was real surprised to see a very heavy ejector mark on the case. This was the thirteenth firing on the case. I am well up to speed on properly bumping the shoulder. There is a question coming! Somewhere around the 8th or 9th firing I switched from the three die system to a Redding FL bushing die. I seem to remember when setting up the die I over re-sized a coupe cases. I kind of blew it off and and kept going. After buying a set of comp. shell holders and readjusting I ended up with a +.006" shell holder to get .001 head space. Is it likely I ruined the case at that time and it just showed it's ugly head? I have a small awl bent on the end similar to the bent paper clips. I have checked approximately 30 cases and have not caught on a low spot in any. Not really sure how it should feel though. Any suggestions will be appreciated. Thanks. Frank

 

[bigedp51]

I tossed my bent paper clip in the trash and bought the RCBS Case Mastering Gauge after I started collecting the British Enfield rifle. At maximum military headspace and shooting thin rimed American cases you can have .017 head clearance.

Using this gauge and measuring case wall thining in the web area you will never have a case head separation.

 

[Keith Glasscock]

I'll second Ed's advice. The case master is actually a reasonable tool - especially for the price.

Now I've got a question: On the case master, the "probe" is sharp on the end. I'm always afraid I'm going to make a scratch, and subsequent stress concentration, inside the case. Has anyone else out there considered this? What could be done to prevent a problem? I'm thinking a ball-end on the probe would be a good thing. I just don't have the first clue how to make one. Ideas?

Thanks,
Keith

 

[bigedp51]

I'll second Ed's advice. The case master is actually a reasonable tool - especially for the price.

Now I've got a question: On the case master, the "probe" is sharp on the end. I'm always afraid I'm going to make a scratch, and subsequent stress concentration, inside the case. Has anyone else out there considered this? What could be done to prevent a problem? I'm thinking a ball-end on the probe would be a good thing. I just don't have the first clue how to make one. Ideas?

Thanks,
Keith

You don't need to make a special probe, you stone the tip of one you have to prevent blunt force trauma to the inside of the cases innards.

(get my point?) ;D

 

[Keith Glasscock]

Not a bad idea - think I'll steal it.

I was wondering if I could drill a hole part way into a piece of steel shot - might be entertaining to try.

 

[bigedp51]

Not a bad idea - think I'll steal it.

I was wondering if I could drill a hole part way into a piece of steel shot - might be entertaining to try.

Below is the first .303 British case I checked on the RCBS gauge, after I sectioned this first test case I stoned the tip after seeing the scratches. After stoning the tip and sectioning and checking more cases I had no further scratches inside the cases. Adding a larger ball to the tip may give you false readings, ANY thinning in the web area even .001 is a sign the case is stretching and a warning of excess head clearance.

The factory loaded Winchester .303 British case below stretched .009 on its first firing and the rifle headspace was well within SAAMI specifications. BUT these cases had thin rims and were not made to military standards meaning case wall thickness and were junk after the first firing.



Adding a "ball" could give you half a reading as it "spanned" the gap in the brass.

(get my point?)

 

[Keith Glasscock]

I get your point

My case master is going to get "stoned" tonight. Should I try to keep the tip around .010" across?

Different question - how much ring depth do you allow before junking a case? I have an arbitrary number I use with my 308. I've either been adequately conservative in that number or darn lucky.

 

[bigedp51]

Different question - how much ring depth do you allow before junking a case? I have an arbitrary number I use with my 308. I've either been adequately conservative in that number or darn lucky.

I don't have a set figure, it depends on the case type and the chamber, once the case stretches and if the the case wall is thinner on one side, the case will warp and become banana shaped. Meaning the base of the case is no longer 90 degrees to the axis of the bore, when the case is placed on its base it is actually leaning like the Tower of Pisa.

I wont mention any names but in the photo below the moderator in a Enfield forum told everyone that Enfield chambers were drilled off center. He didn't understand that commercial American SAAMI .303 cases were not made to British military standards. The case diameter, chamber diameter and head clearance have the greatest effect on stretching and warping. When resized the case warps even further with brass springback and the bullet is out of alignment with the bore.



The NECO gauge advertisement enplanes it best, and is why many people buy Lapua brass and have tightly chambered rifles.



If you want a quick education on case stretching, bullet runout and case head seperations just buy a British Enfield rifle and shoot American made SAAMI brass in the rifle.

 

[K22]

Just curious - didn't you see any signs of incipient separation, i.e. a faint sharp line around the circumference of the case?

 

[searcher]

As k22 noted, you will "usually" see a faint hairline crack forming and if you don't notice this right off, you will end up with what occured. My first and only happened with my 7mm Rem Mag. I was shooting a warm load and it occured after loading #8. I am so used to getting so many more loadings out of my benchrest rifles, I just didn't pay enough attention to how quickly my brass was degrading. I pulled the bullets on the remaining batch and ALL were on the verge of just starting to show faint cracks or had a crack visibly forming. Because your other cases do not show signs of problems - it could be that you had inflicted a stressor on the few that were oversized - as you stated could be the problem - but I would think it had to have been really stressed to do this?? As for how your bent awl should feel when you do detect the thin spot where it may seperate, when you apply just slight pressure (enough to maintain firm but gentle contact) against the awl, pushing it against the inside of the case and drawing it from the base towards the neck, you are looking for the feeling of the awl dropping into a depression that is typically rather narrow (perhaps 1/8"). If you have a case ready to seperate, you will KNOW when you go over one. It is quite noticeable and hard to miss if you go over the case a few times. Over time, you be able to feel them "coming on". If I can feel pronounced, easy to identify depressions that ARE SHORT (again the 1/8" or so), I'll smash the brass and throw in my recyle box. Be sure your awl has a very fine point (about like a fine point ball point pen or less) or you may not feel the dip. O.K. to hone it so you don't scratch the brass but I wouldn't worry about that much - as you shouldn't be using enough force to do any heavy scratching. The sharper the better in my opinion as a sharp tip will just plain "stop" in the groove of a really bad case.

 

[Old Navy]

Just curious - didn't you see any signs of incipient separation, i.e. a faint sharp line around the circumference of the case?

My last barrel was a 6BR. The cases outlasted the barrel. I took for granted the BRX cases would too. My bad! I am in the process of checking them visually and with my awl. My awl has a fine point but not sharp like a scribe. Thanks to those that addressed my question. Frank

 

[Keith Glasscock]

Gotta show off the incipient head separation I found today. The "groove" measured .012 deep at its worst. The case was .021 at its thinnest spot (near the head).

Note that the bright line was not straight around the case. Neither is the groove. That is the first time I've actually sectioned a case. Had to see what was inside...

Ed, notice no scratches? Got that point figured out.

 

[Keith Glasscock]

Oh yeah, forgot, that case shot an X @ 600 yards on its last firing - as messed up as it was inside, you'd never have known it on the target.

 

[Bindi2]

G-day Ed good to see you still have the right answers

 

[bigedp51]

G-day Ed good to see you still have the right answers

Good to hear from you Bindi2, I sold off the majority of my Enfield collection but I do miss you Ozmanics and your great sense of humor. Say hi to Son and Lithy for me, and tell Vulch I hope all his Enfields rust.

Ed

 

[bigedp51]

Oh yeah, forgot, that case shot an X @ 600 yards on its last firing - as messed up as it was inside, you'd never have known it on the target.

Busdriver, I learned a great deal collecting mil-surp rifles with their fat long chambers and shooting commercial brass. If you can fire form a case on the first firing without any case stretch you are home free. In articles here on the home page they fire form with a normal high pressure charge. If done this way and the new cases have excess head clearance the cases will stretch.

I have seen new .243 cases that were much shorter than SAAMI manufacturing tolerances and over .009 shorter than a GO gauge. When fire forming short cases like these I use a reduced load and jam the bullet hard into the rifling to hold it against the bolt face to prevent stretching.

The problem with this for competitive shooters is you have more bullets down the tube and more barrel wear. The type and quality of your brass, meaning the thickness and hardness of the brass in the base area means a great deal. The military sets higher hardness standards for its cartridge cases in the base web area.

 

[22BRGUY]

Any chance on that case you coulda forgot to remove the case lube?

 

[lurcher]

I have been toying with the idea of getting a tool to allow me screen brass for "banana'ed" brass. I know this can be done with the neco tool. There is also an argument that says that echecking case neck wall thickness will also alert you to banana'ed brass but I am wondering if the RCBS case master used in the way that you are demonstrating would be a cheap and viable alternative to a neco tool for this purpose?

 

[Old Navy]

Any chance on that case you coulda forgot to remove the case lube?

That is possible. I am shooting 185 cases with this barrel. I went through them all looking for an external ring. I found five. I could just barely feel a little catch on four and one is really bad. It has a very clear grove around the exterior. I am going to open it up tomorrow. Later! Frank

 

[Bindi2]

G-day Ed good to see you still have the right answers

Good to hear from you Bindi2, I sold off the majority of my Enfield collection but I do miss you Ozmanics and your great sense of humor. Say hi to Son and Lithy for me, and tell Vulch I hope all his Enfields rust.

Ed

Sorry to hear about the sale, can do Lithy & Son, Vulch has gone to the dark side and dropped of the radar.