G20 KB! - Ideas on what happened?

Started by pasky2112, August 29 2012 01:01:29 PM MDT

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pasky2112

Well, I had my first KB! yesterday.  Fortunately the G20 held strong and just the mag well vented most of the discharge.  Also, some came out of the slide/frame gap and made it's mark on my thumb.  I THINK pieces of the follower or the top plastic part of the mag that blew off is what hit me in the face...right cheek (I'm a lefty).  After I came to my senses and counted to ten on each hand, I started trying to piece together what happened.  I was working up a load from the Hornady 7th... trying to get 180g' JHP's to 1200'/s

~~~
Stock G20/stk bbl with 22# SS RSA
NEW Starline brass
180g JHP (montana golds)
AA#7 @ 12g w/ CCI#300 LPP
seated COAL 1.255" and crimped with Lee FCD
Location in FL - ~80-85* and VERY humid; breezy; ~60' ASL (near coast)

With 10 rnds in mag, I fired the first rnd @ 1253 fps.  Brass casehead was .433" BUT didn't hit target (paper plate @ 15y)...I'm not THAT bad.
Case had usual bulge for hot rnd out of stk bbl...no smiles or other chamber lines noted.
Fired rnd 2.  Same results but 1220 fps... not rnd on target, either.  The case was in same condition as first.  At this point, what was on my mind is why the heck was I not hitting a freakin' 8" target @ 15yds! 
Fired 3rd rnd which was the KB.  It crossed my chrono at 1135 fps.  The pistol blew out of my hand fwd about 3-5' and the mag exploded down dumping the remaining 7 rnds around me.  The mag is completely 'self disassembled'.  After I checked out all the G20 frame/slide/bbl/RSA parts for anomalies, I (maybe foolishly), fired a factory HDY 155g XTP that was in my 'carry mag'.  I hit @ POA at the expected speed of around 1300 fps.  I collected everything, packed up and went home to my family, thank God.

I think that's all the facts.  Any ideas on how i could have gone from a guppied case to a full rupture?  Double charges ruled out; no room for powder or bullet.  No bbl obstruction; previous rnds crossed chrony and cases were recovered and assessed.  This IS a max load according to the HDY book I used but it's not the first time I loaded to max...even in .40 in my G23.  I'd expect the brass would have shown symptoms of over-spec pressure in previous rnds of that load b4 blowing on me?
I attached 2 pics of failed case... not sure if they'll show up in post or what.

WHEW....



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What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4

sqlbullet

I don't have my Hornady data near me...At work and all.  Accurate Arms website shows 11.0 grains of #7 to be a max with a 180 grain Rainier HP, with a pressure of 36,200.

The real disconcerting part of the report for me is the absence of a hit on target with the first two shots.  That seems to indicate something screwy.

EdMc

First, glad you're okay. Only comment I can make is Hornady's 8th ed. shows a max of 12 gr, AA#7 @ 1200 fps from a 5 inch barreled Colt Delta. This being with a COL of 1.260 and Hornady 180 gr XTP. It took 0.6 gr to get from 1150 to 1200.
Length of bullet difference? I don't have the experience to say.

pasky2112

Quote from: sqlbullet on August 29 2012 01:14:30 PM MDT
I don't have my Hornady data near me...At work and all.  Accurate Arms website shows 11.0 grains of #7 to be a max with a 180 grain Rainier HP, with a pressure of 36,200.

The real disconcerting part of the report for me is the absence of a hit on target with the first two shots.  That seems to indicate something screwy.

Screwy indeed.  That's part of the reason I stopped and examined the cases immediately.  I didn't see any signs of excess pressure on the 2 previously fired cases.  I know there aren't any guarantees but what concerns me is that there were no obvious warning signs... then KAPLOW!  I DID have flattened primers but those were also showing up on initial lighter loads and are apparently common for AA#7.?

I load on a Dillon 550b but when I get to max loads, like these....no matter caliber/platform, I stop and weigh ea. charge on a dig scale.  As far as crimp goes, I just take out the flare.  It may be overkill, but i even use a Redding Comp Seating Die with a mic. 

In hindsight, since the Accurate max charge is significantly lower than the HDY max charge, I should have stopped at the Accurate max.  But I've loaded .40's to the HDY max w/ AA#5 which was also higher than the Accurate max and never had any problems.  I loaded Blue Dot to max in 180's and 155's from HDY 7th, as well, with no probs.  FWIW, I've never even loaded to the point of getting a Glock smile/frown... EVER.  I've only seen bulging to various degrees depending on stock or AM bbls in my G22/23's.  I felt pretty confident that I wouldn't have KB'd based on signs of pressure and the solid G20 platform.  But you can clearly see the case rupture is an outline of the unsupported area of the chamber.  Like I said, I measured the case head area outside the web on the 1st two cases and got .433.  Even at .434, I would have expected to see chamber lines before a blown case.  :-\

What do you make of the circular split in the case?  Could this be a defective case coupled w/ high pressures?  I added a pic of my chamber with a rnd in it to get an idea of case support...or lack-thereof.  But it doesn't seem excessive or alarming to me. 

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What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4

pasky2112

Quote from: EdMc on August 29 2012 02:58:25 PM MDT
First, glad you're okay. Only comment I can make is Hornady's 8th ed. shows a max of 12 gr, AA#7 @ 1200 fps from a 5 inch barreled Colt Delta. This being with a COL of 1.260 and Hornady 180 gr XTP. It took 0.6 gr to get from 1150 to 1200.
Length of bullet difference? I don't have the experience to say.

Thanks EdMc.  I'm bummed yet VERY grateful.  Sure.  It's possible the diff between the MG's I was using and the XTP's in the book could have contributed.  But I've been using the same case of #2500 180 JHP MG's for over a year with the HDY book loads.  I've never even seen a 'glock smile' in my cases before.
Part of the reason I wanted a 10mm was b/c I have loaded .40's to my safe max and that are accurate.  I wanted to go the next step.
What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4

sqlbullet

If I had to guess, I would say that circular split if from where the front of the case, where the walls are thin, was pressed hard enough against the chamber that it could not move, while the back of the case did move.  This may indicate the breach was starting to open prematurely.

And, I have been as guilty as the next guy of cherrypicking hot load data from one source.  Speer is one of my go-too's when I want to document rationale behind a hot charge.

cwlongshot

Glad to hear your OK...

The way I see things, you have three possible problems.

One; OAL... (I am sure you know this) seat the bullets short and pressures go up.

Two; Whe was the last time you checked or calibrated your "digital" scale.  I do not trust them, unless you have spent HUGE DOLLARS they simply are too inaccurate for me. Ill take a balance beam thats easy to adjust and accurate...

Three; A bad case... Was it brand new? (NEW anything doesn't exclude it from scrutiny) Maybe a multi fired case slipped in???

I like progressives, but I only use them for range loads, anything near max I go straight to single stage and weighing every load, (Max loadings) I use a Redding powder measure, with most powders its set to two grains light and trickle to level. Don't beat yourself up too badly, hind site is always 20/20. Use it as a learning experience. Don't forget it, screw that case to your bench where you will see it every time you weigh a charge.

Again, glad you are OK...

CW
NRA Life Member, NRA Certified Range Officer, NRA Certified Pistol & Shotgun Instructor, NRA Rifle & a Reloading Instructor.

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pasky2112

Quote from: cwlongshot on August 29 2012 03:56:58 PM MDT
Glad to hear your OK...

The way I see things, you have three possible problems.

One; OAL... (I am sure you know this) seat the bullets short and pressures go up.

Two; Whe was the last time you checked or calibrated your "digital" scale.  I do not trust them, unless you have spent HUGE DOLLARS they simply are too inaccurate for me. Ill take a balance beam thats easy to adjust and accurate...

Three; A bad case... Was it brand new? (NEW anything doesn't exclude it from scrutiny) Maybe a multi fired case slipped in???

I like progressives, but I only use them for range loads, anything near max I go straight to single stage and weighing every load, (Max loadings) I use a Redding powder measure, with most powders its set to two grains light and trickle to level. Don't beat yourself up too badly, hind site is always 20/20. Use it as a learning experience. Don't forget it, screw that case to your bench where you will see it every time you weigh a charge.

Again, glad you are OK...

CW

Thanks CW.  It's true that my COAL was .005" short and that's (+/-) 1-2 1000's honestly.  I don't think measuring the JHP is that accurate in the .400 JHP MG's.  The 'petals' on the meplat are rough and can easily throw off a measurement to the .001".  I would think I'd see the first 2 rnds show signs of pressure, though, since they were within the same tolerances.  Little things can add up.  Almost everything in this lot of rnds was new... new brass, 1st pound of AA#7, new G20, even myself!  I'm new to 10mm. so I'd expect to make mistakes.  But that's why I'm so careful...or thought i was.

Yes, no doubt the brass was never fired.  I just got the batch from Starline and set them aside for these max loads.  I had no other brass or powder on my table.  I haven't calibrated my scale in about a year.  I have a 100gram wt and I'll check it ASAP.  I use my Dillon for my F Class and FT-R  HP Rifle match rounds.  Just not wham-bam progressively and not with Dillon dies.  I'm almost as meticulous with max pistol rnds.  I don't case prep and check runout, etc. but I verify everything and don't load for quantity unless It's a pet load I know is GTG.

But the points you make are good.  Usually a disaster happens when a lot of little things come together at the same time.
too much charge per Accurate data...
bullet type diff from guide... (MG vs. XTP)
.005" short COAL...
possibly a weak case...
unsupported case area in chamber...
inexperience...

It's just that I've always read...and it makes sense... that you have those pressure signs like chamber lines in Glock to look for if ur getting too close to the red line.  Aside from flat primers, I didn't see any of those signs. 

Any good solid bullet pullers out there?   ;D  My cheesy blue plastic one broke off at the cap after 5 rnds.

Thanks again...

- Dave
What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4

pasky2112

Quote from: sqlbullet on August 29 2012 03:38:01 PM MDT
If I had to guess, I would say that circular split if from where the front of the case, where the walls are thin, was pressed hard enough against the chamber that it could not move, while the back of the case did move.  This may indicate the breach was starting to open prematurely.

And, I have been as guilty as the next guy of cherrypicking hot load data from one source.  Speer is one of my go-too's when I want to document rationale behind a hot charge.
Yeah, I was thinking something similar.  When I pick up my G20 off the grnd, it was slightly stuck back out of battery.  I thought it was toast the way it violently exploded out of my hand.  But i just racked the slide and ...dink...out came the mangled case.  I think the charge ignited, and the bullet left the case.  Either when it went into the leades or sometime b4 it left the muzzle, pressure spiked violently WHILE blowback was beginning to eject the case out of batt.  Before the case left the chamber, if failed.  This is evident by the crescent shape of the hole near the case head.  Then everything jammed at some point when the case was almost torn in half....starting at one side of the case (6:00 o'clock) but not completely tearing all the way across.  I dunno...it's just how I picture it.  The main thing is that I want to learn what happened to help other and prevent it from happening again, should i decide to go back to working up max loads.  I was hoping you uber gurus could wave your wands and give me an answer.   ;)  besides take up Archery...not that there's anything wrong with that.   ;)

You nailed it on the cherrypicking.  I didn't think there was anything wrong with doing that until now.  There's such a diverse body of data out that it was nice to have an 'anchor'. so-to-speak.

Thanks everyone for your input.  It all helps.

- Dave
What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4

sqlbullet

Glad you are ok in any event.  This is one shooting experience I haven't had to date, and hope to never have.  I had a couple of mis-fires in my Garands with WC846T that a standard primer just wouldn't quite get started properly.  Same day I had a bullet stuck in the bore of my CETME in .308 from the same powder, same problem.  Pulled them all and reloaded the cases with Varget, and then switched to Magnum primers for all my surplus powder.  Problem solved.

I have two RCBS kinetic bullet pullers.  Both have been great.  I bought one, then recently inherited the other.

And, I second the comments about digital scales.  I have one I use to weigh cast bullets, looking for internal voids.  But if I want an accurate measurement you can't beat a balance beam scale.

pasky2112

Quote from: sqlbullet on August 30 2012 07:40:32 AM MDT
Glad you are ok in any event.  This is one shooting experience I haven't had to date, and hope to never have.  I had a couple of mis-fires in my Garands with WC846T that a standard primer just wouldn't quite get started properly.  Same day I had a bullet stuck in the bore of my CETME in .308 from the same powder, same problem.  Pulled them all and reloaded the cases with Varget, and then switched to Magnum primers for all my surplus powder.  Problem solved.

I have two RCBS kinetic bullet pullers.  Both have been great.  I bought one, then recently inherited the other.

And, I second the comments about digital scales.  I have one I use to weigh cast bullets, looking for internal voids.  But if I want an accurate measurement you can't beat a balance beam scale.

Thanks.  I appreciate the good will.  I hope you never do, either.  I'm a little skiddish about getting on the horse again, to be honest.  I feel like the time I got rear-ended at an intersection pretty badly.  Once i recovered and started driving again, my adrenaline spiked every time i saw a grill in my rear-view mirror!  ;)

The worst I've ever had happen to me prior to the KB was one squib way back when I started loading .223 on a progressive.  I felt defiled.  But no physical damage was done and you gotta move on.  I just started loading pistol about 2 yrs ago primarily in .40.

My G20 looks and feels GTG.  I fired the factory load after the KB and it was nominal.  I think I might take a chill break for a while and pull my bullets.  Maybe shoot some factory loads I have... to get through any apprehension.  In the meantime, re-examine my pistol loading ideals and research scales, etc.  Also, I'm guilty of 'shooting for power' and the odds got even.  (Although I still don't understand why my previous cases didn't show any signs of excessive pressure)  So, like my rifle loading, I'm going to shift gears to loading for accuracy as a priority... even in the 10mm.  ;)  Thanks again for sharing.
What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4

Phoenix Photos

#11
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uz2bUSMC

Think there is a chance your progessive snuck in a really light charge?
10mm enthusiast since '98.

When you have hits on target with your feet moving, you're a shooter... all else is target practice.

pasky2112

Quote from: 10d on August 30 2012 01:53:58 PM MDT
Maybe your crimp wasn't tight enough.If a bullet sets back upon chambering it will cause pressure to go way to high.If you want a hot load maybe using AA 9 is a better way to go in a glock.It fills the case and is a slow powder.Always good to make sure your crimp is good.Sometimes a die can back out a little.10mm's have strong recoil springs and I put a pretty good crimp on my handloads.I push my bullets into the side of my bench after setting the crimp and make sure they hold then measure to check for setback.Glad you didn't get hurt.
Thanks.  I was very fortunate.
Possibly.  When I set up my dies or change to different bullets, I check my crimp/FCD by measuring case mouth with my mic.  Essentially, I adjust it until it flattens out the flare.  I did measure the OAL of the remaining rnds in the mag and they were unchanged. 
If anything, I may have had too tight a crimp.  But I've used the Lee FCD since day one loading .40's and set them up the same way.  In fact, a habit I picked up from loading match rifle rnds is that I pull the first 2-3 rnds I make and check the bullet for deformities (ring, deep scratches, etc.) for consistent neck tension.  I do that for max loads in .40/10mm as well.  It's the only way I know how to check for OVER crimping/neck tension.  But it's possible in those other loads, a tight crimp didn't matter as much as it did these... who knows? 
What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4

pasky2112

Quote from: uz2bUSMC on August 30 2012 03:16:07 PM MDT
Think there is a chance your progessive snuck in a really light charge?

I scaled checked ea rnd.  Anything 11.9-12.0 I accepted.  Else, I dumped and recharged.  I was working on a new max load with a new powder so I made extra sure.  I only loaded 20 test rnds so I didn't mind the extra time.  But, yeah, I'm tracking ya.  Progressives can swing either heavy or light depending a few variables.
What part of "infringe" don't people understand?
Glock 10-ring #2112
G20, G29SF, G23 Gen4