New build, failure to extract spent shell, charging handle hard to pull back

[Ateup]

Ok, need a little help. Built my grendel from ground up. First time out to test fire and had failure to extract, charging handle very hard to pull back. 3 rounds and I aborted effort. Research lead me to think it was an undergas issue and case was swelling causing it to be stuck in chamber. Bought gas block alignment tool and reinstalled my Jp adjustable gas block and found that it was slightly off so thought that was problem. Headed to range today with adjustment screw on block out 1 turn. Same issue. Took another turn out of screw and same issue. After 1st FTE episode I removed firing pin at home and was able to manually charge and eject live rounds no problem. Any ideas? Thanks in advance.

20" odin barrel
JP bolt
Fail zero BC
hornady black ammo

[Rickc]

For some reason it is a common problem with the grendel. Happened to me. After you run 20 rounds through it.problem will go away.

Open that gas block all the way, Lubricate the hell out of your bolt carrier and shoot.it.

Easiest way i found to unjam it was to separate the upper.and.lower and tap on the bolt carrier inside the upper.

[Klem]

For some reason it is a common problem with the grendel. Happened to me. After you run 20 rounds through it.problem will go away.

It is not a common problem with the Grendel.

There will be some technical issue common to both of you, but there's no evidence it is common. Or peculiar to just this calibre.

[Rickc]

Well do a little search on this forum. Failure to extract.

But it is easy to fix. Use an adjustable gas block and open it wide open, lubricate the hell out of the bolt carrier on break in and shoot the hell out of it. I reccomend factory ammo on break in. Eliminates one variable

If you follow most of these threads the gun just magically begins to cycle properly.

[rabiddawg]

I agree with klem. It's not an inherent problem with the round. All mine are built by Alexander arms or Precision Firearms and they ran from the start. A properly machined and assembled Grendel is no more likely to fail than any other.

[Bigs28]

Headed to range today with adjustment screw on block out 1 turn. Same issue. Took another turn out of screw and same issue.


hornady black ammo

First do you have the detent model gas block or the adjustment screw with locking set screw?

When you say you backed it out 1 turn, did you mean a full 360 or just 1 click of the detent? Straight from jp on using detent model.

2. Back the adjustment screw out one full rotation (six clicks). Load a single round into the
magazine, chamber it, and fire. If the bolt doesn’t open at all, open it another four clicks and
try again. Most likely, the bolt will short stroke at this setting. If that is the case, clear the
rifle before proceeding.

I feel you are not opening it enough and still undergassed.

[A5BLASTER]

I agree with Bigs28, your gas block is closed off to much open it up a good bit more and retry.

Mine did the same thing when I first put it together and that was my problem, my barrel uses rifle length gas just like yours and I use the JP gas block as well and I had to start the block at half open, if I started lower then half open it would do the same thing you said yours did.

What model of JP gas block do you have?

[VASCAR2]

Some barrel manufactures don't drill the appropriate size gas port hole. There have been barrels sold with under size gas ports and many with over size gas ports. It can be difficult to tell the difference between under gassed and over gassed system on a new build.

It always helps to identify the barrel length, and gas system (ie, pistol, carbine , midlength, intermediate or rifle length). Manufacture of the barrel, whether Stainless Steel or CMV with type of rifling and twist doesn't hurt either as some brands are known to have issues. It's a good idea to measure the gas port diameter on a troublesome build that way it is easier to help diagnose the problem.

[LRRPF52]

For some reason it is a common problem with the grendel. Happened to me. After you run 20 rounds through it.problem will go away.

Open that gas block all the way, Lubricate the hell out of your bolt carrier and shoot.it.

Easiest way i found to unjam it was to separate the upper.and.lower and tap on the bolt carrier inside the upper.

I've lost count on how many 6.5 Grendels/uppers I have built now.

I don't know what I'm doing wrong, but they all just seem to work right out of the gate, like all my other AR15 builds.

I just haven't seen FTExtract that I can recall, come to think of it. Could be my memory going to crap too though, so who knows...

OP: What's your buffer and recoil spring set-up?

What's your gas port diameter?

A 20" should have a RLGS and a .094" port.

When you say "out 1 turn" on the Adjustable Gas Block, does that mean 1 turn from closed? Is so, there's your problem-nowhere near enough gas. Keep opening it until you get lock back on the magazine, then open it another half turn or more, considering weather conditions and their effects on the gas system when they get warmer or colder. Colder will require more gas, hot will require less.

[Ateup]

Thanks everyone for replying. I just tested the gas tube flow by tying a baggie over end of my muzzle and putting a spent casing in the chamber and attached a small tube to end of gas tube in the upper. Flow at 2 full turns out from closed (adjustment screw does not click) did seem restricted. Made one more full turn out and it seems to flow much better. Going to head to range asap to give it another go.

BTW: I do not know what the gas hole in the barrel (20" odin stainless) is sized and the gas tube is rifle length. AR stoner rifle buffer with JP tuned and polished buffer spring. Jp gas block is the model with the set screw in front and side adjustment screw. 4 barrel clamp screws at bottom.

[Lastrites]

After 1st FTE episode I removed firing pin at home and was able to manually charge and eject live rounds no problem. Any ideas? Thanks in advance.

Call yourself Lucky, one should never remove the firing pin and then proceed to start racking an AR. Luckily the cam pin didn't turn on you and cause one of the worst jams of the carrier you would likely ever experience. Word of advise, don't try that again or you will be back asking how to get it unstuck.

The above is a mute point if you did remove the cam, but you didn't mention that you had so I thought I would share.

[Ateup]

Call yourself Lucky, one should never remove the firing pin and then proceed to start racking an AR. Luckily the cam pin didn't turn on you and cause one of the worst jams of the carrier you would likely ever experience. Word of advise, don't try that again or you will be back asking how to get it unstuck.

The above is a mute point if you did remove the cam, but you didn't mention that you had so I thought I would share.

Don't remember if I removed it or not but thanks for the advice. Makes sense.

[AZBackcountry]

If you're still having problems ejecting after proving the gas tube/block aren't the issue look at your bass. Look for scratches. Run a caliper up and down the sides of the brass looking for bulges, bumps, rings or egg shapes. There will be ejector pings at the top of the neck and are normal. It could be a chamber flaw since unfired rounds cycle easily. And "charging handle very hard to pull back".

[Texas]

I've lost count on how many 6.5 Grendels/uppers I have built now.

I don't know what I'm doing wrong, but they all just seem to work right out of the gate, like all my other AR15 builds.

I just haven't seen FTExtract that I can recall, come to think of it. Could be my memory going to crap too though, so who knows...

OP: What's your buffer and recoil spring set-up?

What's your gas port diameter?

A 20" should have a RLGS and a .094" port.

When you say "out 1 turn" on the Adjustable Gas Block, does that mean 1 turn from closed? Is so, there's your problem-nowhere near enough gas. Keep opening it until you get lock back on the magazine, then open it another half turn or more, considering weather conditions and their effects on the gas system when they get warmer or colder. Colder will require more gas, hot will require less.

I have built nine 6.5 Grendels in the past three months and they all have functioned well from the start. It does sound like you are under-gased, and I would agree that you need to open up the gas block, and if that doesn't work, recheck the gas port alignment.

[Texas]

Call yourself Lucky, one should never remove the firing pin and then proceed to start racking an AR. Luckily the cam pin didn't turn on you and cause one of the worst jams of the carrier you would likely ever experience. Word of advise, don't try that again or you will be back asking how to get it unstuck.

The above is a mute point if you did remove the cam, but you didn't mention that you had so I thought I would share.

I have a couple of "show pins" left over from when we use to display the rifles, and we ground the end of the firing pin so that it would not protrude through the bolt. If they were not in the bolt, someone would check the weapon and it would lock up -- food for thought.

[sk8inrj1]

Ateup, did you get your FTE malfunction diagnosed and/or fixed?

[Ateup]

Ateup, did you get your FTE malfunction diagnosed and/or fixed?

Haven't been able to get back to the range. Will post asap. Thanks for inquiring.

[Drillboss]

I've lost count on how many 6.5 Grendels/uppers I have built now.

I don't know what I'm doing wrong, but they all just seem to work right out of the gate, like all my other AR15 builds.

I just haven't seen FTExtract that I can recall, come to think of it. Could be my memory going to crap too though, so who knows...

OP: What's your buffer and recoil spring set-up?

What's your gas port diameter?

A 20" should have a RLGS and a .094" port.

When you say "out 1 turn" on the Adjustable Gas Block, does that mean 1 turn from closed? Is so, there's your problem-nowhere near enough gas. Keep opening it until you get lock back on the magazine, then open it another half turn or more, considering weather conditions and their effects on the gas system when they get warmer or colder. Colder will require more gas, hot will require less.

I can still count mine: One 5.56, four Grendels and a 300 blackout. All ran fine with fixed gas, except for one of the Grendels. That one had problems with some starting loads. Turns out I had scanned the instructions rather than reading them. A slight adjustment fixed the issue.

Based on what I've read here, if I ever do try an adjustable gas block, I think I'll start out wide open and work down from there.

[Lightstrider]

So would you guys recommend going with an adjustable as block from the get go?

[Sticks]

So would you guys recommend going with an adjustable as block from the get go?

I think the consensus is that a standard gas port from a quality MFG is good to go, unless you plan on shooting suppressed, or your barrel gas port is suspect.

Quality barrel, proper gas port, standard gas block - no problems. Minor fine tuning can be done with buffer weights and or springs