Mini boom

[vluc]

This past season I have had 8 instances of a mini kaboom, where the lower part of the brass blows out, the bullet is fired, no damage to the gun, but a good sting to the hands and powder blowing down through the trigger area onto my hands.  I stop myself, check the gun for squibs (there are none), then continue shooting.  Running a Glock 34, Gen 4, 13# ISMI spring, 4.5# striker spring in Carry Optics - the normal setup I used on my G34 Gen 3 in production.  Load is 147 grain Zero JHP, 3.3 grains of Titegroup, COL 1.14.  Again, the exact load I have been running for years.

 

Only happens in the Gen 4's, had it happen to my main and backup gun in consecutive runs.  Brass is range brass collected from the 2017 Area 8 and 2017 Western PA Section.  Checked for problems, loaded and every round chamber checked.

 

Brass always ejects.  Here is what it looks like.  These pics are not of every one of the rounds, issue is the same an each one, they could all be clones.  Brass has mostly been Win, primers on 7 of 8 were win, one cci.  This one was literally the last round shot out of a 130 or so round local match last Sunday

 

I am perplexed, I can shoot a match 2x, 250 plus rounds and not have it happen, go weeks with no issues, then boom.  Probably shot close to 6-7K rounds, all from that same collection of brass.

 

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Edited November 1, 2018 by vluc

[Dwbsig]

Just my opinion the brass is work hardend from being sized and fired to many times basically just wore out brass.

[Frank705]

In my experience 3.3gr is getting a bit hot and if you have the Glock barrel it has an unsupported area. Hence what is called a Glock Smile. I’d back down the load to 3.1 or under.


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[vluc]

I suspected it's bad brass, tossed some when going through it when I first got it back in '17.  Some splits, some cracks, tried to make sure that what passed muster looked fine.  Never know...

 

Can't say the load is too hot since it is, literally, the exact load and size I ran when shooting production from 2002 to 2014.  Had to be 70K I've reloaded and run through the Gen 3 Glocks and this never happened, not once the entire time.  Never a squib, never a double charge, never a single issue since I started reloading

[Dwbsig]

Well maybe the gen 4 barrel is different from the gen 3 as far as case support can you see any difference by doing a visual inspection?

[rishii]

Could it be firing out of battery

I’ve picked up 9mm brass fired out of a glock that passed a case gauge, and from what I’ve seen glocked brass seems to a problem with 40 not 9

[Sarge]

Are those primers pierced? Looks like it in the pics? Are you sure they are not setting back? Maybe grab a small bucket full and try pushing them against the bench and checking to see if they shortened? The primers look nice and rounded but the hole might be a pressure sign.

[Sarge]

2 minutes ago, rishii said:

Could it be firing out of battery

I’ve picked up 9mm brass fired out of a glock that passed a case gauge, and from what I’ve seen glocked brass seems to a problem with 40 not 9

I thought that as well. Maybe the recoil spring is tired and a little dirt builds up and it doesn't close fully. Only takes a smidge. I can't tell from the pick but see if the striker marks look off centered on the blown cases. Thats a sign of firing OOB.

 

[galt11]

I use almost the same load in a Gen4 34 and a Gen4 17 with either Fed or Win SPP and range brass.  I do use all factory recoil springs.  I haven't had any issues and have even used up to 3.5 grs.

[galt11]

1 minute ago, Sarge said:

I thought that as well. Maybe the recoil spring is tired and a little dirt builds up and it doesn't close fully. Only takes a smidge. I can't tell from the pick but see if the striker marks look off centered on the blown cases. Thats a sign of firing OOB.

 

 

I was thinking the same thing, but could be an artifact from the picture.  Please let us know

[vluc]

Striker hit is centered, primer not pierced.  Hit looks exactly the same, compared the boomed ones to others shot at the same time.  No difference to me or the group I shoot with who are perplexed as well.  GM's and M's with more years than I can count of shooting and reloading.  All springs have been replaced a few months ago, thought they might be part of the problem as well.

 

I've run captured and non-captured springs in both my main and backup guns.  This has happened in both guns, by the way.

 

Gen 4 and Gen 3 barrels are interchangeable.  I had run a gen 3 barrel in one of the Gen 4's thinking that the barrel in the 4 was different. Gen 3 ran without a hitch, but then, so does the 4 more often than not..  Remember we are talking 8 out of thousands fired.

Edited November 2, 2018 by vluc

[Sarge]

32 minutes ago, vluc said:

Striker hit is centered, primer not pierced.  Hit looks exactly the same, compared the boomed ones to others shot at the same time.  No difference to me or the group I shoot with who are perplexed as well.  GM's and M's with more years than I can count of shooting and reloading.  All springs have been replaced a few months ago, thought they might be part of the problem as well.

 

I've run captured and non-captured springs in both my main and backup guns.  This has happened in both guns, by the way.

 

Gen 4 and Gen 3 barrels are interchangeable.  I had run a gen 3 barrel in one of the Gen 4's thinking that the barrel in the 4 was different. Gen 3 ran without a hitch, but then, so does the 4 more often than not..  Remember we are talking 8 out of thousands fired.

Well in that case I don't think its the gun. It would probably happen more often if the gun were the cause. What about checking for set back? Try that to at least rule out something. Then I would focus on the brass or even powder drops.

[Dwbsig]

I had a case rupture about two years ago out of gen 3 glock 34 and I contributed it to a piece of brass that someone had shot a hot load in or wore out brass but it could have been case set back but it hasn't happen since. Lol

[HI5-O]

Maybe some of that brass you collected was shot out of some 9 major open guns? I know some shooters who load used brass for lost brass matches. 

[superdude]

Probably time to invest in new brass. Old brass or questionable brass picked up at the range could be overused and weak.

 

Best to start with some new brass that you know the history of.  Brass, even paying for new brass, is cheap compared to the cost of an injury. 

[chevrofreak]

In 50k rounds of reloaded 9mm I have only ever had 1 blown out case and it was in a PCC with a 3.4gr charge of TiteGroup under a 147 plated RN.  The brass was an EGA case, and it was one of my cases that had been previously fired as a 9major. 

[razorfish]

Looks like an out of battery detonation. If your COAL is a few thousandths too long for one of those barrels, a striker fired weapon will still fire.

The hint here is that you had eight rounds blow out in a single barrel. That pretty much rules out bad brass and the limited damage rules out a double charge.

Plunk test both barrels... your rounds should drop in the chamber and spin freely without contacting the lands.




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[vluc]

3 hours ago, razorfish said:

Looks like an out of battery detonation. If your COAL is a few thousandths too long for one of those barrels, a striker fired weapon will still fire.

The hint here is that you had eight rounds blow out in a single barrel. That pretty much rules out bad brass and the limited damage rules out a double charge.

Plunk test both barrels... your rounds should drop in the chamber and spin freely without contacting the lands.




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Had done the plunk test, rounds drop and spin fine. All chamber checked fine. 

Oal is well within specs, and the 8 are split between 2 different Gen 4 glocks.

 

Leaning towards the brass. Fortunately, the brass from that collection is done. Unfortunately, I have a few thousand already loaded. 

[Hi-Power Jack]

I've fired about 50,000 rounds of 9mm Major thru my two TruBors, without incident.

 

After getting my 2nd TruBor back from the gunsmith a few years ago, I had three

similar brass explosions (range brass, WAC, 124 gr JHP), all within a few weeks.

 

And, nothing since.

 

I found two of the three pieces of brass, and they were BOTH WW.

 

Never figured out exactly what happened - went thru the same discussion here at BE

and the same possibilities - never resolved the problem.

 

BUT, the problem went away, all by itself - same bullets, powder, charge, brass and same

gun - NOTHING changed, but the problem went away by itself.

 

The same ammo in the other TruBor NEVER caused a problem.

 

 

[perttime]

Will that Glock fire if the slide is out of battery?

[Sarge]

19 minutes ago, perttime said:

Will that Glock fire if the slide is out of battery?

It shouldn’t. But I had an M&P that would. Striker mark was right on the edge of primer.

[perttime]

I know that my Glock doesn't fire out of battery. There's something wrong if it does.

[RePete]

11 hours ago, Frank705 said:

In my experience 3.3gr is getting a bit hot and if you have the Glock barrel it has an unsupported area. Hence what is called a Glock Smile. I’d back down the load to 3.1 or under.


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That's the load I've been using for 4 years and never a problem.  All fired from 2 gen 3 G34's.

[MikieM]

From the looks of your primer and head stamp there doesn't appear to be any excess pressure. The lack of stretch marks also rules out the notion that your gun is coming out of battery too early. This is highly unlikely in a retarded blow-back system, anyway. 

Since the case rupture is only on one side I would deduce that a portion of the case head is unsupported by the chamber.  At least to the extent that it allows the occasional weaker case to blow out. Check some of the spent cases that you didn't have any problems with for bulges at the case web area.

 

Also, if it's possible, use a different barrel for awhile and monitor the results.

[Steve RA]

Some types of chemicals will weaken brass, when using range brass you really can't tell what may have been done to it previously.