Hey folks,

Recently took my 10.5" pistol build out to the range, about 3 rounds downrange and the gas block exploded into 4 pieces and sent the gas tube flying. Gas block is a Joe Bob adjustable version and gas tube is a brownells pistol length. Checked for proper gas tube length in the upper receiver, no problems there. Tube was properly aligned, dimpled barrel for the block and torqued down properly and used blue loctite on the set screws. Any idea why this might have happened? Plan on contacting JBO to figure out the next course of action.

Probably a bad heat treat on the metal, or it had a hairline crack somewhere.  
I'm gonna go with a fluke failure.  If it had been something else, like overpressure or a barrel obstruction, you would have had damage to other components on your weapon.  

Was it an aluminum gas block?  If so, don't buy aluminum gas blocks.  They expand and contract at a different rate than the steel barrel and can cause leaks and even slip.  
Still, nothing that should have caused a catastrophic failure of the gas block.  Worst case, your gun wouldn't cycle correctly.

Got any pictures yet to post, would like to see this kaboom.

Aluminum no name brand?

It's most likely due to defects in the gas block.  You should be able to tell from looking it over.  

Although improper heat treat is possible, it's not terribly likely.  They get treated in batches, and most likely would have issued a recall on them.  However, a call to JB would probably give you some information.  

Other possibilities:
1. your gas tube was plugged - this also shouldn't be a problem, as the gas block should be engineered to be able to handle a locked up bolt.  I avoid the melonited gas tubes because the innards get plugged with salts and other process shit.
2. Gas block oriented way off kilter.  Also shouldn't have caused a KB, should have just refused to cycle.
3. Complete fluke, we have no idea what could possibly have happened.

I can't see how anything you did during install would have caused it to split, as it essentially shouldn't cause a catastrophic failure.  
How many rounds did you have through it before it split?  Was it on the first shot?  or after a low round count?  A few dozen rounds?
What material is it?  Aluminum transfers heat at a much higher rate than steel does, but the coating should slow the transfer between the two materials slightly.  
How tight was it when you installed it?  Did you have to press it in place?
Is it a clamp-on gas block?

Got pictures?

I believe it is aluminum. Sticking with steel gas blocks from here on out. Here are a couple pics of the carnage. Kaboomed on the third round fired.

Attached File


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That's a bummer, I've had great results with the SLR's.

Curious to see what joe bob's is going to do.

From Joebob's description of their adjustable gas block. Interesting situation, glad no injuries involved.

Technical Specs
Includes set screws
Nitride/Melonite QPQ finish
USA 4140 chromoly Steel
Machined in the USA
Weighs 2oz
Internal Diameter 0.750
Fits inside all handguards
Same profile as our standard low-profile gas block
Includes (2) set screws for attachment
Includes 10-32 Set-Screw w/ 4-40 Retaining Screw (Left facing)
Accepts standard gas tube roll-pins but a roll-pin is NOT included.

Well DaYum!  Easy fix luckily

That makes me reconsider the one I just put on my rifle.  I picked up 2 of those gas blocks a while back, and just recently installed 1.  I haven't tested it out yet since reassembly.

+1 on the SLR adjustable gas blocks, they're worth the money.  

As 42junkpile mentioned above, be sure and check your gas tube if it's melonited as they can be plugged with debris from the treatment process.  
My preference is melonited tubes because I don't care for anything shiny on my rifles, but I've run across a tube that had this problem once.  (Lesson here - have spares on hand)
All that said, it still shouldn't have caused a catastrophic failure of the gas block; it wouldn't be any different than if you had the gas turned all the way off.  

Looking at the specs, it appears the gas block was steel.  More than likely just a materials defect that slipped past QC.  I don't really think it was anything you did wrong.  
Hopefully Joe Bob's will make it right with you.  Let us know how it turns out.

I wonder if it was an ERGO adjustable block branded as Joe Bob's?
Had bought one several months ago and shortly after received a phone call from my lgs where I purchased it and was told it was being recalled due to possible explosion. I ended up exchanging for standard.

I shot my rifle with my newly installed joe bobs adjustable gas block.  It stayed together.  I ran 4 or 5 mags total adjusting it so it would lock back on steel case ammo.  Worked great.

I had the same thing happen to me on a 7.5 with adjustable Radical Firearms GB.  I reused an old roll pin.  It bent and did not go all the way through the gas block.  Because i was being cheap and lazy it cost me more money.  It wasnt the RF GB because i was test firing two new pistols both the same length and both with the same GBs "twins".  The other was just fine.  Once it happened and I inspected i knew right away the root cause and kicked myself in the butt.