50 bmg case failures

[bubbapug1]

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I had a large amount of failures on some IMI 50 bmg brass while shooting my 50 bmg M3HB. The brass in question was on either its 3rd or fourth loading.

I took a very close look inside my chamber after 6 case seperations out of 50 rounds, a very high failure rate.

I don't see too much if any damage except a very slight bright ring which matches the area where the cases let go. I was thinking I would see much more damage, perhaps even be able to feel some erosion.

I am beginning to think the streching from resizing and than repeated firings makes the cases fail but not upon the final firing, and its the final extraction of the shell while hot, still sticking a bit to the chamber walls, which causes the final failure, otherwise I would see more damage.

If the case failed while firing I would imagine the bolt face pressures would be almost catastrophic, and there would be bolt face engravings on the head, but that is not what I am seeing. If I let the shell cool completely I don't need a extraction tool to pull the rest of the case out, it falls out on its own.

Your thoughts?

 

[Togeneral99]

Re: 50 bmg case failures

Was the brass previously fired in a machine gun?
also have you tried the "bent coathanger" trick for feeling inside the case around the head area for incipient head separation before each reloading?

My guess is the brass was severely stretched BEFORE you got it

 

[longshooter]

Re: 50 bmg case failures

You might be resizing the brass too much, that is, pushing the shoulder back too far, causing excessive headspace. If this is so, the brass will stretch a little more, each time that it is fired, causing a thinning in the web area near the base of the brass.

You should quit firing this rifle until you get things inspected, and the problem resolved.

 

[Kells81]

Re: 50 bmg case failures

Maybe your not timing the barrel right and leaving the headspace a little long.

 

[bubbapug1]

Re: 50 bmg case failures

The brass is sized to fit a wilson case gage. If it doesn't fit the gage it won't go into battery. Timing is not an issue on semis.

 

[desertHK]

Re: 50 bmg case failures

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: longshooter</div><div class="ubbcode-body">You should quit firing this rifle until you get things inspected, and the problem resolved. </div></div>

1+ on that. Be safe

 

[Togeneral99]

Re: 50 bmg case failures

http://www.hevanet.com/temple/50reloading.html
Read here about the incipient case splits and the coathanger "trick" I think you will find they are thin in that area before you resized them.
also check to see how much of the shoulder you are bumping back after firing indicating excessive headspace. You definately don't want excessive headspace in a caliber that large <3" from your face.
Just my thoughts

 

[longshooter]

Re: 50 bmg case failures

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bubbapug1</div><div class="ubbcode-body">The brass is sized to fit a wilson case gage. If it doesn't fit the gage it won't go into battery. Timing is not an issue on semis. </div></div>

Using your Wilson gage, what is the difference in length of a non-resized case, fired in your chamber, and the same case, after resizing.

 

[shoots100]

Re: 50 bmg case failures

Usually an oversized case would fail on the first firing,or show signs of failure.I think that your batch of IMI cases have gotten weak after three (hot loaded ??) firings and are at the end of their lifespan,or you "mistakenly" had it headspaced a little too loose with the second firing of the cases.It happens.IMI is good brass and I've gotten over 10 (semi hot)reloads out of them in my M82 before they started to show signs of failure.I would cull those cases,pull the rest of the loaded rounds and scrap the brass. My .02
STEVE

 

[SRT_Supply]

Re: 50 bmg case failures

M82 /= M3HB in regards to brass life.

Reloaded ammo that would have been just fine in a boltgun has been known to separate in my M3HB. According to everything I've been told by experienced Ma Deuce reloaders, you're probably looking at about the normal case life on that brass. Short recoil actions aren't particularly kind on brass longevity.

I'd just simply start checking all of your brass after each firing for incipient separation, and throw everything that looks suspicious into the recycling pile to sell for scrap.

This is why it's vital to have a broken shell case removing tool with you any time you take a Browning to the range...

 

[bubbapug1]

Re: 50 bmg case failures

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: longshooter</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bubbapug1</div><div class="ubbcode-body">The brass is sized to fit a wilson case gage. If it doesn't fit the gage it won't go into battery. Timing is not an issue on semis. </div></div>

Using your Wilson gage, what is the difference in length of a non-resized case, fired in your chamber, and the same case, after resizing.</div></div>

The brass is 0.019 to 0.039 inches longer from the datum line of the shoulder, or it has grown backwards that distance. I size the brass to be almost flush (+0.001/- 0.002)on the max length of the gage. I have to do that as it won't load with any longer brass. I think the design of the gun, and the way its held in the chamber is so loosey goosey that the brass can grow.

I bought some PMJ member on the board shot from a bolt action match grade barrel and the brass didn't need to be resized, it fit the case gauge! That brass survivied four firings from the M3 before is showed signs of imminent seperation.