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2011 .40 caseback blowouts


cpa5oh

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I've got an STI Apeiro and, in the last week, I've had 4 case backs blowout.  They definitely aren't over/double-charged rounds - the explosion isn't violent at all and the same batches of ammo have been run through other guns (including another 2011) and I've had no issues.  

 

I know that I had zero extractor tension (had failure to extract incidences the last few times I shot it, checked it, and the extractor wasn't holding cases to the breechface at all - could slide a case right through the extractor and the extractor almost wouldn't touch the case).  Not sure if that could be a cause of case blowouts - I'd imagine that improper tension wouldn't cause blow outs, but maybe a complete lack of any tension at all could?

 

Only other thing I can think is that I remember the extended firing pin being a tight fit in the breechface - might be possible that occasionally it's getting hung up and catching the back of the primer just before the slide closes...

 

Anyone have any experience with 2011 case blowouts and any thoughts on what the causes could be?

 

Thanks!

 

 

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what does your barrel say on top?   does it say AET or just 40S&W?   I had a AET barrel in my apeiro and had several blowouts.   One even exploded the barrel.  The gun was replaced and the new one is much smoother.   Not sure if it was something with the 1st AET barrel but the new one seems much better.  even just taking the gun apart it is much easier.   

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Are you using reloads? If so what weight and type of bullet. What is your powder and weight? Also, what brass are you using. I found in my XDM, a combination of Unique, 180 grain lead bullets, and PMC brass would lead to a case head blowout consistently.

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Barrel is AET.  

 

I am reloading my own ammunition.  180 grain coated bullet with 4.2 grains of Ramshot Competition.  Same reloading setup/load as I have used without problems for the last three years loading .40 (and currently shoot from other guns).  Brass is mixed range pickup stuff.  If I have to start sorting brass to shoot this gun it'll be on gunbroker at a fire sale price :-)

  

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I'm not sure if the AET barrel isn't seating fully and leaving a gap or what the issue is but i had the same problem.   I started using a u-die and the redding G-RX pass through for sizing and it helped the issue but didn't fully solve it.   The new barrel just says 40S&W on top

  

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I don't think anything external is different between an AET and non-AET barrel (could be way wrong, though).  I thought it was just a little difference to the chamber and more difference to the rifling (gain-twist).  

 

Gonna try the factory (non-extended) firing pin, extractor adjustment, and a new firing pin spring and see if that doesn't end the case blowouts.

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11 hours ago, cpa5oh said:

Barrel is AET.  

 

I am reloading my own ammunition.  180 grain coated bullet with 4.2 grains of Ramshot Competition.  Same reloading setup/load as I have used without problems for the last three years loading .40 (and currently shoot from other guns).  Brass is mixed range pickup stuff.  If I have to start sorting brass to shoot this gun it'll be on gunbroker at a fire sale price :-)

  

 

 

Your load is certainly not out of line. I was loading a 180 Gr coated projectile with 4.5 gr of Ramshot Competition. OAL was 1.19-1.20. Velocity was Hi-979 fps, Lo- 934 and Avg fps was 955. Corresponding power factor were: 176, 168, 172. 

 

EDIT: this data was out of a STI Edge (Brazos)

 

Edited by JMike
clarification & spelling, lol
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26 minutes ago, cpa5oh said:

I do load my ammo short (1.130") because I mainly shoot a CZ Tactical Sport in Limited, but that's always been the case and this case blowout shit is a new phenomenon.

 

 

Yeah, your load isn't the problem. There is something else going on here. I have reloaded that short for all types of polymer guns like M&Ps, FNS and H&Ks. 

Edited by JMike
added another one that reloaded for
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Could it be possible the barrel is prematurely coming out of lockup? That would allow the back of the case to be partially unsupported during the firing cycle. I am by no means an expert but, have built a few 2011s. You could perhaps try a heavier recoil spring or hammer spring to see if it made a difference.

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1 hour ago, Gomar83 said:

What is the plunk test? i've never heard of that before.

 

 

Dropping the round into the chamber and making sure it falls out without resistance. 

 

Lately one of my new guns doesn't have enough clearance for coated lead bullets to do this with my normal loads. I suspect it's the reason I was having blow outs too. The bullet rubs and needs to be pressed in. 

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On 3/27/2017 at 7:17 AM, cpa5oh said:

Only other thing I can think is that I remember the extended firing pin being a tight fit in the breechface - might be possible that occasionally it's getting hung up and catching the back of the primer just before the slide closes...

 

 

Most likely this is the problem, or at least part of it.  Chances are the fp is sticking out and setting off the primer before the barrel is fully into battery.

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I do chamber check every round using the Ben stoeger/shock bottle chamber checker.  Rounds that pass that checker all plop right into the barrel chamber when it's clean.  However, that chamber was dirty enough to where rounds weren't plopping in free and clear.

 

i made several changes and ran 100 trouble free rounds through it: went back to the stock firing pin, upped the mainspring to 19 (so I wouldn't get light strikes), tuned the extractor, and cleaned the barrel real well.  Fingers crossed that I won't have more blowouts.

 

thank you for all of the replies they were very helpful.  I'll report back so that in the future if anyone looks this topic up an answer will be in the thread.

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35 minutes ago, ltdmstr said:

 

Most likely this is the problem, or at least part of it.  Chances are the fp is sticking out and setting off the primer before the barrel is fully into battery.

 

I would think if the firing pin was sticking out there'd be problems with rounds getting under the extractor.

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no pressure signs on your primers? Never had a problem with ramshot competition but I was Loading to 1.190 oal. Then again it could be your firing pin as you said.

Edited by bulm540
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14 hours ago, dansedgli said:

 

I would think if the firing pin was sticking out there'd be problems with rounds getting under the extractor.

That's s great point and probably blows up my firing pin getting stuck theory.  Beyond your comment, now that I think about it, I'd have been getting doubles if the pin was stuck hanging out through the breechface.

 

i guess I'm left with a dirty chamber not allowing bullets to fully seat and somehow the gun being capable of setting such a round off.  

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Mark a line on your cases at 12 o'clock with a sharpie and make sure it is loaded by hand one at a time, so the line is at 12 o'clock.  After the round is fired , look for any type of bulging in the case.  That would show something is not supported.  Check to see if you have enough tension on the bullet as well to make sure the bullets are not being set back in the case when they are loaded.  Put a line around the bullet and case mouth as a round is fed, then remove the round to see if the bullet is being driven back deeper in the case.

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21 hours ago, dansedgli said:

 

I would think if the firing pin was sticking out there'd be problems with rounds getting under the extractor.

 

Typically, yes. But not always.  Somehow the case has to be pretty far out of the chamber for the head to separate.  The bottom of the case just ahead of the extractor cut is pretty thick.  So it's not going to blow out, even if it's unsupported (at least with a normal powder charge).

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AET barrels have tight chambers. I've had issues with my SV's and .401 coated bullets, but .400 bullets (blue bullets and fmj) don't cause me any issues.  Is it possible hat your bullets are .401 and either keeping the gun slightly out of battery but within reach of your extended FP or being crammed into the tight chamber and suffering set back??

 

I'm not a gunsmith, but I had reloading growing pains when switching to the AET barrels and figured I'd relay some of my experience. Blue Bullets case gauge better than FMJ in my hundo. 

Edited by tha1000
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17 hours ago, troupe said:

Mark a line on your cases at 12 o'clock with a sharpie and make sure it is loaded by hand one at a time, so the line is at 12 o'clock.  After the round is fired , look for any type of bulging in the case.  That would show something is not supported.  Check to see if you have enough tension on the bullet as well to make sure the bullets are not being set back in the case when they are loaded.  Put a line around the bullet and case mouth as a round is fed, then remove the round to see if the bullet is being driven back deeper in the case.

 

Great idea with the sharpie - I'll do this.  

 

Definitely have enough neck tension - I'm running coated bullets into dies sized with a Lee "U" die and the case has a noticeable bulge to it up at the top where the bullet goes.

 

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16 hours ago, tha1000 said:

AET barrels have tight chambers. I've had issues with my SV's and .401 coated bullets, but .400 bullets (blue bullets and fmj) don't cause me any issues.  Is it possible hat your bullets are .401 and either keeping the gun slightly out of battery but within reach of your extended FP or being crammed into the tight chamber and suffering set back??

 

I'm not a gunsmith, but I had reloading growing pains when switching to the AET barrels and figured I'd relay some of my experience. Blue Bullets case gauge better than FMJ in my hundo. 

 

I don't think set-back could be an issue - with the U die and .401 bullets there's a lot of tension up at that bullet.

 

But definitely the gun being just slightly out of battery because a round didn't completely chamber is a possibility.  The chamber was dirty enough where rounds weren't passing the "plunk" test until I cleaned it.  I've gotten rid of the extended firing pin and cleaned the barrel very good and plan to clean it after every couple of hundred rounds - if that doesn't do the trick I won't be sure what to try next, but I think it's going to work.

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