6.5 Grendel.  VLTOR upper.   Spikes BCG.  Maxim Firearms bolt.

Was out shooting Saturday.  Fired 2 rounds fine.  3rd round fired, but bolt did not unlock.  Fired case still stuck in chamber.

I mortared it.  HARD.  I know how to effectively mortar out a stuck case.  This is not the situation.  Something else is going on.

Took the rifle home, I took the lower off and I am able to pry the bcg back right near the bolt face about 1/8", to where the bolt should begin to rotate.  It's not.  I can see that the lugs are 'lined up' with the lugs in the receiver extension.  I actually bent a fairly beefy screwdriver trying to pry it out.  

At this point, I'm thinking broken lug or something blocking the rotation of the bolt.  What the heck do I do now?  It WON'T move.

UPDATE:

Got it out.  Had to pull the muzzle brake/suppressor mount, gas block, JP tube, take off the barrel nut.  Then I was able to just get the barrel out of the upper past the index pin.  Put the brake back on and used it and a muzzle device wrench to crank the barrel just a little to get the bolt to release.

Behold the carnage:











It looks like 1 lug broke on the previous shot (it was not in the barrel extension and I know it didn't fall anywhere, I was purposely working in a very clean area) as I only recovered 3 of the 4 missing lugs.

I would estimate that bolt has about 600 rds fired.  This is the 3rd bolt I've broken in this rifle (previously I noticed cracks or a single missing lug) all at around 750-1000 rds.  It never broke bolts before I started using a suppressor on it, so I'm guessing the backpressure is all screwed up or something and the bolt is being driven backwards before it's ready?.  It has a JP adjustable block that's turned way down, but every once in a while I'll notice the set screw has backed out and the gun is overgassed.  For reference, I fired close to 3k through it with the original bolt, put the suppressor on, and it broke within ~750 rds.  

I guess I need to look for a different gas block that has positive settings and does not allow the screw to just randomly back out.

(oh and for the record, I know it looks filthy.  I cleaned the entire gun, bolt and carrier were spotless less than 50 rds ago.  I think alot of the gunk is the oil I was squirting in there trying to make something happen)

Remove gas block, pull gas tube, unscrew bbl nut....

Profit?

And then what (although that was next course of action. )?

If it's locked up this tight, how am I going to rotate the barrel?  I don't know if I'll be able to pull the barrel out of the receiver past the index pin to allow it rotate?

keep mortaring or try a punch and hammer to drive the bcg back maybe?

reloads?  May have popped a primer.

check headspace?  chamber might be too tight and the pressure on the bolt is holding it tight against the locking lugs?

Ummm, if you can't get it out doing that, you could drill the index pin out, and unscrew the bbl from the bbl extension.

Does a cleaning rod go all the way down to the chamber?

Factory ammo.  This rifle has broken bolts before, with a suppressor it's just too much backpressure and eventually shears a lug.  I think this it what happened here.

Yeah, then what?  LOL.  Still have the bcg and bolt locked into the upper.

Yes, a cleaning rod reached all the way down.

If you drill out the index pin, then you can turn the bbl extension loose from the bolt.  That's going to extremes, but the bbl could still be put back together w/ the original bbl extension.

ETA:  once the bbl extension is removed, the bolt should be able to rotate, and the bolt carrier should be able to be removed.

Well?

Busy at work and was there til 1130 last night doing taxes.  Maybe I'll have time tonight!

Keep us posted.

Interested to see what was the cause.

You could always send it to Adco, in case you didn't think of that.  They can even send it back shorter.  

wow... just, wow...

Holy cow. I'd never heard of maxim firearms until this thread. Do you think it's a manufacturer problem or its that seriously overgassed?

Maxim bolts are what most Grendel guys consider the Tier 1 bolt.  Pretty much the best you can get.

I'm going with overgassing, or it's even possible that something is out of square on the receiver face.

I'm going w/ over gassed, particularly as the problem started after you added the suppressor.  Carbine or mid-gas?

Glad you got it apart, and glad those remaining lugs held.

Carbine gas.  16" Black Hole Weaponry barrel.

Any suggestions on an adjustable gas block?

What's that one that has 3 settings, kinda a slider that they drill @ the factory?

So, you are loosing a bolt approximately every 750 rounds?

Hand loads or factory?

You might what to back down on the chamber pressure a tad.

This less of an "over-gassed" problem and more of a "over-loaded bolt" problem.

good deal, glad you got the bolt out! fwiw, i squared up my receiver when i built the gun and check the bolt lugs from time to time when cleaning and noticed they seem to be wearing evenly from mating up with the barrel extension lugs. if your bolt lugs aren't mating up evenly with those in the extension it might cause some lugs to be overpressured and give way. just thinking!



Bruce

front fell off

Factory ammo.  Fired 3000 rounds before the suppressor with no issues.  Add suppressor:  Bolt Breakage.  

If it was chamber pressure, why no issues without the suppressor?

OST

OP, this is what I was thinking of:

http://micromoa.com/govnah-gas-blocks/

It gives you up to 3 positions of gas, on a sliding plate.

So with all that said would a good adjustable gas block mitigate some of this?

A suppressor changes the shape of the P-T curve.  While the peak pressure will not change the blow-down pressure will, giving a higher average pressure.

Backing down the chamber pressure will reduce the overall stress on the bolt.

I really like the govnah design with the restrictor plate you can drill your own ports in.  Easy to swap between a suppressed and unsuppressed setting.

 

On this rifle, I only ever shoot it suppressed anymore.  Perhaps changing buffer weight (it currently has an H1 buffer) along with a new gas block?  The JP just won't hold its setting. Even driving to the range with the rifle in a case, the set screw backs out MANY turns.  That's why I'm wondering what kind of GB you guys are using that actually KEEPS the setting you want.

If I were to change buffers, would I go heavier?