Well I've had a chance to look things over. 

First, the frame is junk.  Cracks only appear when torque is applied to the frame.  Yahoo, about $3 a shot in frame cost, as I had maybe 200 rounds down range

I had a number of rounds, both loaded and fired to measure to see where the trouble may have occured.  Those measurements just don't seem to lead me to answers, so I figured I'd post here for others to supply informed thoughts.

First, the load was 11.5g of Power Pistol behind a 135g Nosler bullet.  I have shot 12g prior with no issues, but that was virgin starline brass.  This loading was previously fired, mixed headstamp brass. Primers are CCI 300 large pistol.

Measurements, loaded rounds. (Results are VERY uniform)

OAL 1.253"
Base diameter .424"
primers seated .005" below flush
Powder was dispensed with a RCBS chargemaster, which weighs every charge. About 3 out of 50 threw .1g over, and these were returned to the hopper and re-weighed.

All of the loaded rounds I dropped into the vertical stock glock barrel dropped into position with a satisfying "clink".  I have a difficult time believing the same wouldn't happen behind the pressure of the Gen4 recoil spring.

Measurements, fired rounds.

Case head .433" in 3 of four cases.  .432" in the remainder.
Case mouth measurements are running in the  .424" neighborhood.
Primers are not showing much if any flattening.

The KaBoom happened on shot 11 of the 15 shot mag.  The next round up measured 1.242" OAL, but it was subjected to 5 digit pressures from the ruptured case, and some erosion of the lead may have also occured.  The other rounds were within .001 of the original OAL.

The case would indicate either firing out of battery, or a premature unlocking of the action with the round in the barrel.  This was not an overload, over pressure event.  I tend to believe it unlocked early because the round left the barrel and was in the group at 7 yards.

Perfection isn't the work that comes to my mind with respect to Glock.  I'm lucky to have walked away from this unhurt, except for the cost of the gun.   

Greg

People love them. One thing always seems to be a common denominator from people with more knowledge than I will ever have!

Tim Sundles (Buffalo Bore)- "The new Glock model 20 comes with a recoil spring that allows the breech face to open too soon and my new Glock model 20 will get extreme spreads of about 100fps with the factory spring installed."

Mike Williard (Swamp Fox Ammo)- "Ok, here is what I have come up with for those that are interested, whoever they may be. I am going to continue to sell ammo but with the following conditions.
This may limit my sales but what is actually done with the ammo is no longer going to be my direct responsibility, although maybe shared and will require colaboration between myself and anyone that is interested in buying ammo.
All ammo will be specified as requiring a fully supported chamber and an increased recoil spring. as is required by other similar manufacturers.
These could be aftermarket or factory fully supported chambers, including match grade barrels etc. If there is any question an evaluation will need to be done to insure the barrel has a fully supported chamber. Some pistols come this way from the factory, S&W 1006 and SA XDM's come to mind.
The springs are generally available for most pistols, in the event of no spring available, a somewhat lighter load will be offered.
Each purchase will require a small consultation between myself and the buyer to understand the application and the requirements for the ammo.
I will offer a fully supported chamber barrel and spring for any glock, 1911 or other pistol that does not meet the chamber/spring requirement at just very slightly above costs.
Lone wolf offers barrels for most glocks and offers, IMO the best support overall. KKM and Storm Lake also offer for glocks and also for 1911's but at a higher price. I have dealer accounts with each of these and will facilitate a barrel for the purchaser.
Some pistols that are known to have insuficient chamber support are glocks, dan wesson, and possible others.
Each pistol model will have to be evaulated to determine the support if no other data is available.
All ammo will be listed on my site as requiring a fully supported chamber and increased spring except ammo for revolvers, which are currently offered at slightly below max book speeds and pressures anyway.
I am firmly commited to safety and high performance at the same time but cannot compromise safety for the sake of performance.
I cannot accept responsibility for the design of firearms that do not meet the criteria that is required for Max pressure ammo.
Having said that, The ammo that has been currently offered has been very successful in practically all firearms with the exception of just a few.
These few firearms will absolutely fall into the category of fully supported chamber only.
Most of the others will be eligible at the owners discretion as to whether they are functionally safe. G20 falls into this category. Its at the owners discretion. But if an issue arises, It better have a fully supported chamber and increased spring in it.
I will make the current offereings the same as before but will add my disclaimer that no g29 will be sufficiently robust without an aftermarket chamber and spring.
The same is true from my own tests of Dan Wesson. There are others and they will be idenitified and listed and I grow this list.
I will post this in my terms of service and will be absolutely clear that any use of this ammo outside of the above mentioned terms is in violation of the terms of service and will not get any support from SwampFox Ammo. Only firearms that follow these guidelines will be covered.
I will be enhancing this statement and will post it in my terms of service on my site.
Anyone that purchases from my site will have to agree to the terms of service. anyone that does not agree will be prohibited by making a purchase."

Wilson Combat- "This can't happen in a 1911. Maybe a Glock or something else."

In response to this: "Someone may have already mentioned this, but I have seen guns fire without complete return to battery, which conceivably leaves a bit more of the case exposed. Happens more frequently when shooting LSWCs."

Quote from: Intercooler on December 05 2013 08:15:04 PM MST
Happens more frequently when shooting LSWCs."

LSWC? 

I'm listening, perhaps too late, but listening. 

I would think the manufacturers would err on the safe side (too heavy of a spring) but I guess not.

Greg

What barrel and spring did you have  on the kaboom?

  The Cor-Bon 135's with 10.4gr's of Power Pistol gives 1456 FPS. Another grain might give 100 FPS increase making that a really warm load for sure.

Quote from: Intercooler on December 06 2013 02:52:33 AM MST
What barrel and spring did you have  on the kaboom?

All stock Gen4

Greg

Quote from: Intercooler on December 06 2013 03:24:50 AM MST
  The Cor-Bon 135's with 10.4gr's of Power Pistol gives 1456 FPS. Another grain might give 100 FPS increase making that a really warm load for sure.

Quikload show chamber pressures in the 33k psi range.  It shows 12g getting close to 37k.

I did a step up loading previously and the rounds with 12g were fine as far as case expansion.  You simply couldn't tell where the feed ramp was on a fired case.

The factory double tap 135 smiled three cases out of a clip load,  and the cases went in the trash. 

I certainly felt safer with the PP load, wrong again.  Underwood 135's seemed fine too.

Greg

What's the plan? Warranty or just buying another frame?

And, have you talked to Glock about this?

It certainly sounds to me like a cap was busted before the gun was fully in battery, and that is a mfg issue.  They may or may not concede the point, but worth a shot anyway.

Glock at the very least will sell you a new frame for $50-$60 if I recall from others that had the same issue not covered by warranty.  If it were me I call and politely ask about a frame replacement because your was damaged, after they inspect it they may provide warranty based on some recoil spring issues and change outs.  At the very least they may just make the gun whole again at your cost which will get you back in to the Glock pistol shooting again.

Call...

GLOCK, Inc.
6000 Highlands Parkway
Smyrna, GA 30082 U.S.A.
Tel.: +1 770 - 432 1202

Quote from: Geeman on December 05 2013 07:53:25 PM MST
Case head .433" in 3 of four cases.  .432" in the remainder.
Case mouth measurements are running in the  .424" neighborhood.
Primers are not showing much if any flattening.

FWIW, from my own testing i found that i was not comfortable going beyond 0.428 on the casehead for a fired case, this was using new starline brass... i based this on measurements from Parabellum Research 200gr production rounds going at 1250 fps...

Rapid fire shots or slow fire?

Quote from: mlk3454 on December 06 2013 09:36:33 AM MST
Rapid fire shots or slow fire?

Slow.  I'd say two seconds per shot.

Greg

Quote from: Intercooler on December 06 2013 06:28:26 AM MST
What's the plan? Warranty or just buying another frame?

I'm working my way through some big disapointment.  I was expecting a safe firearm, and I need to be confident before I will consider using it again.  Glock frowns on aftermarket parts.  It sounds like I need a stronger spring to make it safe. 

I let someone else shoot it a couple hours before it went bang.  Do you know how bad I would have felt if it failed in his hands?

I'll contact Glock early next week and see what they say.  I guess its likely both trying warranty AND getting another gun.  The more the merrier.

Greg

Greg

Quote from: Geeman on December 06 2013 05:41:24 PM MST

Quote from: Intercooler on December 06 2013 06:28:26 AM MST
What's the plan? Warranty or just buying another frame?

I'm working my way through some big disapointment.  I was expecting a safe firearm, and I need to be confident before I will consider using it again.  Glock frowns on aftermarket parts.  It sounds like I need a stronger spring to make it safe. 

I let someone else shoot it a couple hours before it went bang.  Do you know how bad I would have felt if it failed in his hands?

I'll contact Glock early next week and see what they say.  I guess its likely both trying warranty AND getting another gun.  The more the merrier.

Greg

Greg

Having recently purchased the same gun, I am interested to know the outcome.  You definitely need to give Glock a chance to evaluate and remedy the issue before trashing the  brand IMHO.   I did buy the 2 port LW barrel too though.