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First Ka-boom shooting 9mm major


d3ydx3

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Went to the range today for a practice session to shoot my BUL SAS2 UR that I've probably put 1300 rounds through at this point. My standard load is now 9.6gr of AA7 @ 1.160 OAL using a 124gr FMJ, so nothing special. The load runs the comp well and feels good. About 100 rounds into the practice session, I had my first Ka-boom. After a few seconds of shock and making sure I had my fingers and no punctures, I see the magazine spring laying on the ground along with the rounds that were left in the magazine, as well as the base plate for the 170mm mag, which is plastic and has been sheared off. It also looks like shrapnel hit my RTS2 or I dropped the gun on the gravel - good thing the magazine decided to blow itself apart and lose the rounds if I did drop it. Luckily, the ruptured case was still in the gun and and hadn't fully ejected.

 

One of two things could've been the cause or both. I've probably reloaded this case 2-4 times to major and possibly minor before that. I've also noticed my Dillon likes to drop few extra tenths of a grain on the first case when starting a reloading session if it has been sitting awhile. There was a case where I remember thinking it had more powder than usual, but nothing crazy. If you know AA7, then you know 9.6gr fills a good portion of the case volume. 

 

At this point I'm either thinking recycle my major brass less and be more careful with the powder drops. Maybe always throwing out the first drop if the powder has been sitting awhile. 

 

Pics below.

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Just thinking out loud, but the primer does not look as if it saw extreme pressure.  Also, the rupture extends beyond the extractor groove, suggesting an out of battery firing.  With the number of rounds fired prior to this one, there could have been some debris that prevented the slide from going fully into battery.  With the light springs commonly used in Open guns, it may have allowed the slide to be far enough to allow the disconnector to move, but not fully into lock-up.

 

 

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There are a number of possible reasons for this.  One is weak brass.  The bullet hit the feed ramp, because there was not enough neck tension, was set back, that increased pressure; kaboom.  The case itself could be weak in that spot.  Or, out of battery as mentioned above.

 

I also load with SWMP or AA7.  My practice is to buy fully processed, roll sized, once fired, same headstamp brass (RP now), load it once and leave it one the ground.  I do police my brass after practice sessions and load it for Open minor of PCC minor for SCSA.

 

Also, I've abandoned the practice of trying to set my Open guns up to shoot major and minor.  It is not a good idea, because shooting major in such a setup is hard on the gun.  So I set my USPSA guns for major only and run 10 in one and 11 lb. recoil spring in the other.  169 PF ejects just fine.  140 PF leaves the case still in the chamber.  However, my minor Open gun runs 140 just fine.  Heavier recoil springs help drive the gun into battery.

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@zzt @Rnlinebacker@Guy Neill

 

Thanks for the feedback guys. I really hope it wasn't out of battery. I am running AA7 and the gun was kind of dirty, so the debris story is possible. Here's a pic of the primer. Any chance the powder dropper taking me from 9.6 to say 10.5 or 11 with a 124gr bullet could've caused this? I've run 10.0gr loads before in the gun and it hit 180-185PF, which is way over what I needed so I backed it down.

 

I'm also running a 9# spring, which I don't think is horribly light. 

 

If it was OOB, what could I do to troubleshoot? I have tested the disconnector by slowly locking up the slide, and it appears to be working just fine. 

 

IMG_1045.jpg

Edited by pealandco
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The case looks more like a case failure than an overpressure or OOB.  The primer does not look bad and the rupture in the case looks melted rather than blown out, almost like there was a crack in the case web ahead of the extractor groove and the rest of the case was just torched out.

 

What does the chamber look like and was there any other damage to the gun other than to the magazine?

 

Nolan

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I’ve shot that same load for 4 years at least 40 k. Just range brass an never seen this. It is dirtiest powder on the planet but honestly I think it be damn near impossible to over charge it. I think it was out of battery 

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3 hours ago, RJH said:

I think it was just weak brass. Do you have a picture of the other side of the case?

 

Here are some more pictures of the case. There is a slight buldge/very thincrack that runs along the bottom 5th of the case and turns in towards the extractor groove. The case rupture is also oddly symmetrical and almost looks like a mirror of the feed ramp.

IMG_1047.jpeg

IMG_1048.jpeg

IMG_1049.jpeg

Edited by pealandco
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2 hours ago, Nolan said:

The case looks more like a case failure than an overpressure or OOB.  The primer does not look bad and the rupture in the case looks melted rather than blown out, almost like there was a crack in the case web ahead of the extractor groove and the rest of the case was just torched out.

 

What does the chamber look like and was there any other damage to the gun other than to the magazine?

 

Nolan

 

No damage to the gun. The chamber looks fine. I shot another 100 rounds after the KB to confirm function, and no issues at all. Here's what a dummy round looks like when chambered just to see the case support if anyone is interested.

IMG_1050.jpeg

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Rebarrel gun to .38super. 
I started in Open in 9major. I observed that the very high pressure of 9major (even in ipsc pf 160+) and any slight OOB and/or slight weakness in the brass due to repetitive reloading could very much end up to kabooms. This was my very reason to shift to .38s. 

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I've had one 9MM case just completely separate around the rim.  Blue Dot under a 115 grain hollow point.  Didn't even know that had happened (CZ85) till it wouldn't chamber the next round.  Tried to cycle it a second time and then looked and saw the bottom of the case walls sticking out of the back of the chamber.  Weak case?  No damage to the pistol at all.  Just dirty rounds, dirty breech face and dirty in/around the top of the frame.

 

Had a 9MM case separate around the rim when trying to pull it out of the resizing die.  Took some doing but finally got the case walls out of the die.

 

Found one during visual inspection of the cases that was cracked partially around the base at the rim/groove.

 

Never seen this kind of stuff in .45 acp or .40 S&W.  Just 9MM and only in the last 3 or 4 years.

 

If it's already weak, it can blow out at pressures that a piece of good brass would not.

 

Here's one.  System won't let me post the other pics.

 

 

IMG_1793.JPG

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Somebody please explain to me how a Browning pattern gun can fire "out of battery" with a reasonably well centered firing pin strike.

The barrel tilts as it comes out of battery.  I have some "misfires" with light dents near the edge of the primer, that I take to have been caused by pulling the trigger with the action not fully closed. 

 

14 hours ago, pealandco said:

The case rupture is also oddly symmetrical and almost looks like a mirror of the feed ramp.

 

This is what we call a Clue.  Also look at the pictures of a dummy in the chamber out of the gun.  An integral ramp is not a guarantee of complete support for an overloaded round.  In well used brass.

17 hours ago, pealandco said:

Any chance the powder dropper taking me from 9.6 to say 10.5 or 11 with a 124gr bullet could've caused this?

 

My word.  My Dillon will drop a LITTLE extra powder after sitting a while or after a skipped space lets more powder shake down into the bar, but a grain or grain and a half?  When you are already 25% over book.  

I always check the first three charges when starting up and the next one after a glitch leaves an empty space in the shell plate.  

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41 minutes ago, Jim Watson said:

Somebody please explain to me how a Browning pattern gun can fire "out of battery" with a reasonably well centered firing pin strike.

The barrel tilts as it comes out of battery.  I have some "misfires" with light dents near the edge of the primer, that I take to have been caused by pulling the trigger with the action not fully closed. 

 

 

This is what we call a Clue.  Also look at the pictures of a dummy in the chamber out of the gun.  An integral ramp is not a guarantee of complete support for an overloaded round.  In well used brass.


I had the same question on your Out of Battery point. Sounds like you’re thinking weakness in the brass is the cause here? 

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21 minutes ago, pealandco said:


I had the same question on your Out of Battery point. Sounds like you’re thinking weakness in the brass is the cause here? 

Don’t know about all of them but most barrels don’t tilt right away. The slide will move back some before it unlocks. Maybe there’s excessive headspace on his gun leaving more unsupported brass before it unlocks. Continuous high psi will increase headspace.  Just a thought. 

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The more brass, or any metal, is worked it becomes thin and brittle.  Shooting 9 major is a bit beyond factory specs and looking at the portion of unsupported brass at the feed ramp it looks like you hit the imperfect combo. 
 

Was it slightly out of battery? Maybe, but high pressures, with reused brass eventually will lead to a failure, especially when the base is not fully supported. 
 

Yes I’ve had one base failure, but it was in my Tanfoglio and shooting minor 147 load. The case split just above the groove and made a pshht sound when fired. No damage at all, it did not cycle and the bullet did leave the barrel.

 

There is a danger to this sport and it’s a good thing the OP was not injured seriously.

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20 hours ago, pealandco said:

Any chance the powder dropper taking me from 9.6 to say 10.5 or 11 with a 124gr bullet could've caused this?

 

I see maybe .2-.3 heavier charge (HS6) if I let the press sit for a while between loading sessions. AA#7 is a really fine grain powder so I don't think you would see more than that. I throw one charge and dump it back into the hopper before starting out of an abundance of caution. I also run this aftermarket powder baffle to help keep things more consistent and have found that it tightened up my throw weights. 

https://smile.amazon.com/Prairie-Dog-6-101-Perfect-Powder/dp/B00HYYNWFA/ref=sr_1_1?dchild=1&keywords=perfect+powder+baffle&qid=1620325871&sr=8-1

 

This is the second time recently that I've heard of someone having a kaboom with a BUL gun, the other being TheHumbleMarksman. Sample size of 2 is way to small to draw any conclusions, but it does make me start to wonder if there is a design flaw going on, especially with so many folks here suggesting this could be an OOB detonation. 

 

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7 minutes ago, regor said:

 

I see maybe .2-.3 heavier charge (HS6) if I let the press sit for a while between loading sessions. AA#7 is a really fine grain powder so I don't think you would see more than that. I throw one charge and dump it back into the hopper before starting out of an abundance of caution. I also run this aftermarket powder baffle to help keep things more consistent and have found that it tightened up my throw weights. 

https://smile.amazon.com/Prairie-Dog-6-101-Perfect-Powder/dp/B00HYYNWFA/ref=sr_1_1?dchild=1&keywords=perfect+powder+baffle&qid=1620325871&sr=8-1

 

This is the second time recently that I've heard of someone having a kaboom with a BUL gun, the other being TheHumbleMarksman. Sample size of 2 is way to small to draw any conclusions, but it does make me start to wonder if there is a design flaw going on, especially with so many folks here suggesting this could be an OOB detonation. 

 

 

I've actually been in contact w/ David (TheHumbleMarksman) after my incident. I saw his YT video on a KB last week and thought about it to myself right before this range session where I had my KB. The brass he had it with was range pickups and he has not had any with once-fired roll-sized brass. His KBs were with HS-6 and he has now switched to SWMP/AA7. He is shooting a slightly lighter load than mine (9.3 SWMP vs 9.6 AA7), which is probably close to being the same given the very slight difference between SWMP and AA7. 

Edited by pealandco
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@regor@HesedTech@Farmer@Jim Watson@M1A4ME@RePete@NoSteel@AverageJoeShooting@zzt@Rnlinebacker@Guy Neill@38super@TONY BARONE@BoyGlock

 

As far bullet setback goes, I've tested setback quite a bit by chambering dummy rounds and I haven't had any noticeable setback. 9.6gr of AA7 fills up 97% of the case to where the bullet gets seated, so there would be very little room for the bullet to move back further into the case. I also think that AA7 doesn't compress well, but others can correct me there. I'm using a Dillon sizing die that creates a very nice coke bottle shape.

 

I should also mention to everyone that this practice session was to mainly isolate a stovepipe issue that I've been having since I switched to AA7 from N350 and Silhouette. I wanted to try the factory BUL mags vs the MBX 140mm mag that I've been using in practice and experiencing the issue. I will say that AA7 has been VERY dirty for me with lots of cornmeal in the chamber, rails and other parts of the gun. At times it has made the slide sluggish even with a 9# spring. The goal of this practice session again was to isolate the problem being either mag related and then running the gun fairly dry since others on here have suggested that the AA7 cornmeal is because the gun is too wet.

 

Seriously considering dropping AA7 despite how nice it shoots and going to 3N38 (assuming I can find some). The 1st thousand rounds that I put through the gun were mostly with N350 and it was very clean with zero malfunctions. The feel wasn't very good since it doesn't run the comp well, but at least it was clean. I'm assuming 3N38 is equally clean. 

Edited by pealandco
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