Grendel FTE(eject)

[AZHunter56]

Could the bolt spring be the problem? Since I only have 80 round through it. Can it normally take more breakin rounds to correct the problem?

[tango29]

Try the following things to see if you fix your FTE issue.

1. Check that the gas block hole is lined up with the gas port on the barrel
2. Check that gas block and gas tube is lined up correctly with receiver
3. Polish the extractor claw it may be sharp and sometimes sharp edges
will hold the case too long not releasing it to eject properly.
4. Change the buffer spring could be to light or heavy
5. Change the buffer could be to light or heavy
6. Try different magazies
7. try taking rubber o-ring off the extractor spring
8. try taking a coil off extractor spring
9. http://www.youtube.com/watch?v=fuCinEiYuIQ
10. http://www.youtube.com/watch?v=kYm5UjojDMU



tango

[noone]

I can back up the tips Tango29 has in #7 and #8. I had exactly the same problem, and found that the extractor had so much pressure it pressed the cartridge so strongly against the opposite side of the bolt that the ejector spring couldn't push it out of the bolt's recess quickly enough while the rifle was cycling. Once I reduced extractor spring pressure, the pattern for ejected cases went to about 4-5 O'clock relative to the rifle's muzzle. No more stove pipes, no more failures to eject.

[LRRPF52]

There is a happy balance that needs to exist between the extractor and ejector on the rim of the case. It usually boils down to a sharp extractor that is unforgiving, and also shaves a lot of brass off the case.

The next less common problem is debris built up in the ejector channel, which will seize up your ejector. This happens in guns that are run high volume, or where more shaved brass exists from a sharp extractor.

Investing in a solid bolt disassembly tool will help you maintain the bolt over the long haul, and keep in mind that the ejector spring is supposed to be made from a certain higher grade of wire steel, and is duplicated in the AR15 with the selector detent spring that goes in your pistol grip. Most AR15 companies cut corners on both these parts, using inferior wire steel, so look for quality springs when approaching a manufacturer or replacement.

Colt and AA are two companies that I'm aware of that follow the Technical Data Package when it comes to these critical small parts.

[bwaites]

There is a happy balance that needs to exist between the extractor and ejector on the rim of the case. It usually boils down to a sharp extractor that is unforgiving, and also shaves a lot of brass off the case.

The next less common problem is debris built up in the ejector channel, which will seize up your ejector. This happens in guns that are run high volume, or where more shaved brass exists from a sharp extractor.

Investing in a solid bolt disassembly tool will help you maintain the bolt over the long haul, and keep in mind that the ejector spring is supposed to be made from a certain higher grade of wire steel, and is duplicated in the AR15 with the selector detent spring that goes in your pistol grip. Most AR15 companies cut corners on both these parts, using inferior wire steel, so look for quality springs when approaching a manufacturer or replacement.

Colt and AA are two companies that I'm aware of that follow the Technical Data Package when it comes to these critical small parts.

Yes, but getting small parts from either is impossible!

[stokesrj]

Try White Oak Armament, they supply the high power competition crowd with overwhelming support. http://www.whiteoakarmament.com/xcart/home.php

[Drifter]

Brownell's usually has many Colt small parts and springs for the AR-15.

[Dos Perros]

Hello all,

I've just installed a Lilja barrel with the Maxim bolt they recommend. I made a dummy round with Lapua brass and 123gr Scenar. I did resize the brass but found the shoulder wasn't bumped at all using Hornady comparator set. The bolt carrier group appears to go into battery, trigger pulls fine, forward assist doesn't push it any further forward. But when I pull back on the charging handle the dummy round remains in the barrel. If I tip the gun backwards the dummy round falls out freely and there are no marks on the ogive.

I do notice the bcg goes forward smoothly without the ground in, for example when I push it forward manually with the upper separated from lower, so I believe the gas tube to be installed properly.

When I drop the dummy round in the barrel by hand and try to push the bcg into battery manually with upper separated from lower, I notice it's much more difficult, I probably have to create more than 5 pounds of force before it suddenly pops into place. But it still won't extract as is should.

I notice the rim of the brass is getting chewed up bad, and there is obvious brass markings/shavings on the extractor.

One thing I should say, I can't be sure the bolt is flying all the way forward into full battery, I'm not sure if that can be visually verified or if the rifle won't fire if it's not???

Thoughts guys? Thank you.

[bwaites]

My bet is that your extractor is the issue and that the extractor is not going completely over the brass. Could be a 5.56 extractor, could be a poorly machined extractor, could have a burr on it, there are lots of reasons.

[Dos Perros]

Do you guys know if Maxim is opening up 556 bolts or are they completely machined for Grendel?

[cory]

They're machined to Grendel. The easies way to check this is the OAL. The 5.56 is 2.800", the Grendel needs to be 2.810".

[Errorhead]

Number 5

[QUOTE=tango29;90373]Try the following things to see if you fix your FTE issue.


1. Check that the gas block hole is lined up with the gas port on the barrel
2. Check that gas block and gas tube is lined up correctly with receiver
3. Polish the extractor claw it may be sharp and sometimes sharp edges
will hold the case too long not releasing it to eject properly.
4. Change the buffer spring could be to light or heavy
5. Change the buffer could be to light or heavy
6. Try different magazies
7. try taking rubber o-ring off the extractor spring
8. try taking a coil off extractor spring
9. http://www.youtube.com/watch?v=fuCinEiYuIQ
10. http://www.youtube.com/watch?v=kYm5UjojDMU

Number 5 on Tango's was my culprit, shot a 24" AA over watch for a year or so, got a pinned to 16" (14.5) Saber Defense upper, had ejection problems. Tried two different bolts and two carriers, then tried the bolt out of the AA and still had ejection problems. I had a heavy buffer in one of my 5.56 carbines, put that in the short Grendel, wahla! No more problems. I have run about 400 more rounds thru it without a hiccup.

[PrecisionFirearms]

Does the bolt Lock back on last round with Mag inserted? If so then the gas is sufficient and the problem is most likely in the extractor. We have had problems with everybodies extractors and we make out own now. Even the AA bolts we supply with barrel and bolt combos have to be tweeked to make them work reliably.

Mark Hostetter
Precision Firearms

[Dos Perros]

Hey guys, I disassembled the Maxim bolt extractor and compared to a 556 bolt I wasn't using. The Maxim extractor didn't have an o-ring like the 556 but was otherwise identical. When assembled I noticed the spring tension on the Maxim seemed weak so I added an o-ring and poof it cycles the dummy round just fine. Was able to even shoot it last night and if it gets enough gas it will eject the brass. It won't cycle a new round though, but I believe that to be a gas issue so I will tweak the block as I already planned to do. The groups in the barrel break-in were scary good.

[45r]

The slot. on a grendel should be 10 thou wider than a.556 extractor.
The back of the slot should be flush with the bolt face.
The claw should be the same thickness as a .556 extractor.