Need some input. 6.5x55 Swedish Mauser (M38), Remington cases, CCI primers, surplus military powder well below listed maximum.
Case 1 - blown primer. Fourth round in a series of five. First three showed no pressure signs. Fired last round with no pressure signs. Primer pocket was so enlarged a new primer could be set in by hand and simply fell out. Shot a series of five with 1/2 grain more powder with no pressure signs or other problems. All weighed charges.
Case 2 - A tiny mark approximately 1/8" long and about the width of a ballpoint pen stroke. Rough to the touch, discolored with a ring around it. Located in the MIDDLE of the case.
Appreciated any thoughts you may have on either case. TIA.

I'll give you an opinion on number 1. You definitely were too hot, it could be because you threw a bad charge or the powder is inconsistent, but the charge was way to hot.

List your exact load. Please be sure to provide the diameter of the bullets used and their weights.

Did you confirm both the weight and type of powder used for these loads???

BEJ,

Case 1 sounds like an overload.

Case 2 could have a tiny hole in the side of it.

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saeed@ emirates.net.ae

www.accuratereloading.com

It's scary to think one would screw up a weighed charge, but from the replies, that's what happened. Maybe this is a wakeup call to reevaluate my loading process. Thanks for the help.

Just to throw it out, but if the load was low enough, and the powder slow enough, might this have been a mild form of Secondary Explosion (or whatever it is called?). Seems to meet the criteria (low charge, heavy bullet, slow powder). FWIW, Dutch.

How old is the ammunition? Have you checked the headspace? Was there any foreign matter in that case, tumbling medium, dirt, etc..

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LSF/375

I also have an M38 and this subject is of much interest to me. Please respond with the exact powder & charge weight you used and what bullet was involved.

Charlie Petty wrote an interesting article a few years back on a Swede Mauser being pressure tested in an ammo lab as the company was developing its factory loads. I'll try to relate from memory the story. If I can track down the 'zine that has it in my archives, I'll correct any misstatements made from my oh-so-fallible memory.

*Note* there is no guaratee that the following represents your scenario, but it is interesting. I strongly recommend corresponding with Charles Petty about this. I think he still writes for American Rifleman, and could probably be contacted through them or whatever magazine is publishing his stuff.

Since it happened in a lab, strain gauge pressure readings were available for each shot.

A series of loads with a 140 grain bullet and the same powder charge were fired. They were using a relatively slow-burning powder. The pressure began to rise with each succeeding shot fired, though the powder charge stayed the same.

The pressure curve showed a short upward swing upon ignition, followed by a sharp drop, then a huge upward spike. The lab tech stpped when pressures were over max but before the gun was destroyed. As I recall, after examining the situation, they continued firing the same load and tracking pressures, which continued to climb, and the action let go after another 2 or 3 rounds.

They decided the symptoms looked like: Powder is ignited by primer & starts to burn, pressure within cartridge case begins to rise as expected.

Pressure moves bullet forward into long military throat, dramatically reducing pressure inside the case.

Heavy-for-caliber bullet lodges in long (probably rough) military throat as the pressure in the case was sufficient to discharge the bullet from the case, but not sufficient to overcome friction & inertia and push the relatively heavy bullet from the throat into the bore before the pressure drop occurred.

When the bullet stopped in the throat, it became in essence a blockage in the bore, and pressures elevated rapidly.

Since the bullet stopped moving in the throat, Each shot left more jacket fouling in the throat and made it harder for each succeeeding bullet to be accelerated from a dead-stop in the throat to moving down the bore. Thus, pressure increased with each shot.

Apparently when using slow powders in rifles with military throats, you can reduce a charge too far, especially if heavier bullets are being used. Responder Dutch hit it on the head, I think. If you don't need the velocity that slower powders can produce, move to a faster powder. When using slower powders with long throats, use a mid-to-safe-maximum charge. You might also consider magnum primers to try to ignite more of the powder charge initially.

To be redundant, on purpose, I suggest you try to get hold of Charles Petty to see if he will send you a copy of his article and advise you on any further info that has developed. Then, of course, share it with us. ;-)

[This message has been edited by BigIron (edited 10-01-2001).]

Gun has new barrel, installed by a competent 'smith, so headspace if fine. Any foreign matter in case -- this is a possibility, but of course, nothing noted in fired case or any strange residue in barrel. Bullet is 120gr. Sierra BT. Please note, the first three rounds fired were fine with no hint of any pressure sign. Bolt opened easily and smoothly, primers were still round all around the case, and no cratering around the firing pin indentation. Cases had no obvious problems around the web or the neck.

I have been experiencing the same problem with my M96 and M38. I have come to the conclusion that the problems lies with the brass. I use the exact same load, powder and bullet with Win and Rem brass (the load is 42grs of IMR4350 with 140 Sierra HPBT national match bullets- this is a medium load). Velocity was the same regardless of brass. The difference occurs on the second firing. About 1 in 3 Rem cases split in the middle of each case (not towards the base like you might get from high pressure). I have not seen this with the Win brass even after 5 firings. No other pressure signs can be seen. Therefore, I feel that Remington has produced a bad lot (or two) of brass.
At least, that is my theory,
Shawn

BigIron,

I know exactly the article you are referring to. To add on, what precipitated the test you describe was standard load testing by an ammo company. Phase 1 was pressure barrel testing w/universal receiver -- all OK. Phase 2 was trying the same load in an actual M96 rifle -- rifle blew up but barrel survived. Phase 3 was what you relayed, the M96 barrel attached to universal receiver and strain gauge. Good article but it never completely deduced why the pressure hitch occurred. I suspected a worn throat but that was just a WAG.

One thing about BEJ's story that I'm curious about is the new barel. Could be the neck was chambered a touch short. Headspace with FL resized cases could still be OK but case necks, even when properly trimmed, could be pinched. Given that other rounds shot OK, pinched necks may be far fetched, but it's just a thought. Otherwise check your new rifle against a current lot of cannister powder with a known behavior (e.g., H-4350, RL-19). Use the recommended starting load and work up. Just to be safe, try another lot of brass. If the problem persists, take it back to your smith and have him check it out again.

Good luck and be safe.

Martindog

BigIron,
Your post is exactly what Win. found out about the 243 Win...When the throat wears out on a 243 and you shoot lighter than 100 gr. bullets you get a secondary explosion and the gun blows up...Win. performed these test to determine why more 243's blew up than all other calibers combined...Thought this might interrest you...

Old surplus brass, or any "old" brass that has aged is a source of many problems.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

Shawn460,

I wasn't sure if you were talking of case head seperation or lengthwise splits. Anyhow I do believe that rem 6.5x55 brass has the base diameter of 30-06 or at any rate is smaller than CIP measurements for 6.5x55. I also feel that it is harder. Add in a larger mil spec chamber and you may have an answer as to why splitting occurs.

In addition it may be manafactured shorter so when fired in a rifle will have to stretch more than winchester brass. This will lead to case seperation allthough to seperate on 2nd firing is pretty poor and would lead me to check head space/chamber.

1894,
The splits occur horizontally about 1/2 way along the height of the case. This does not happen with the Win brass. I will mic the two cases and see if the rem cases are smaller. However, I cannot imagine a company like rem doing that poor of a job when making brass! Either way, I plan on avoiding the rem brass for this round in the future.
Shawn

It must be said that you should have this weapon checked by a competant gunsmith for chamber irregularities and head space. Having said that I also wonder if there might be some poor annealing of the rem cases at fault?

Hello,
I am curious about the powder. Surplus military is what it is referred to. Could it have been contaminated during the reclamation process? Like maybe somehow getting a little bit of pistol powder mixed in? Just a little brainstorm.

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Safety & Ethics,Accuracy, Velocity, Energy
Joe M

Ray A. - Thanks for the note on the .243 - very interesting.

My Rem and Winchester 6.5x55 brass is a few thousandths smaller in head diameter than the Scandinavian milsurp ammo I have. I'll be ordering some Lapua brass - on sale at Midway this month, by the way, I believe about $38.00 per 100.

BigIron,
I shoot the 6.5x55 in 5 different rifles, all military, 4 bolt guns one semi. I've gone through case seperations, but never a primer pocket prob. However, I suspected the Rem brass and saw that someone beat me to mentioning it. Another route to good brass is to buy Sellier & Bellot ammo. I have been shooting this for a while and really like it. The price is right, and as a bonus, S&B mics out at the spec dimensions. I am using that brass exclusively in my match loads now.

Eric
Exercion3@home.com

Just what is the "military surplus" powder in use here? The commercial lot to lot difference may be interesting here, or your having used data for a similar canister powder would be a good place to start on question #1 unless you are using some surplus powder designed for a 7.62x39 and got a charge and a half. What is the powder and charge weight?

What was the exact case length on the rounds in question? My guess, one long case and or slighly shorter chamber than spec coupled with a lot lot of surplus powder that is faster than the data used for starting.

I am using some surplus Winchester powder (Vietnam Era .30/06 Machine Gun loads--per the label) similar to Win785 in my 6.5x55's Mauser and Remington, with excellent results. However the loading data that came with the powder was not the best.

The first batch out of the press, with starting loads, produced unacceptable case head expansion, high velocity and excellent accuracy and short case life, (3 loadings)but it drove Sierra 140 Grains at 2900 FPS out of an 1896 M38....case life and accuracy are much better at 2800 FPS and in this case 3 grains less than starting load recommended powder charge.

Item number two seems like a pin hole--the start of a case split.

[This message has been edited by Fish Springs (edited 10-22-2001).]