AR10 Trigger not always igniting primer

[Thumper580]

Sort of strange situation AR10 308... AERO upper and lower, Tool Craft carrier with JP HP bolt... All top shelf components...
Sometimes when I drop the BCG on the first round from the mag and squeeze the trigger, I hear and feel the "click" from the trigger.
Trigger is a new TriggerTech Diamond AR10 trigger. I eject the round, put it back in the mag...do it all over again and it fires fine. It doesn't always do it and may do it on the 3rd or 5th round. Intermittent.

I'm trying to figure out where to focus on. Spotlessly clean the bolt and carrier, etc..... Still intermittent. Hand loads..... Lapua brass, Federal match primers....

Any suggestions would be appreciated.

 

[Redlion]

If you have any other triggers around, I would swap them and shoot.

 

[srt-4_uk]

Are you 100% sure that the bolt carrier is going all the way forward?

 

[USK308]

Sort of strange situation AR10 308... AERO upper and lower, Tool Craft carrier with JP HP bolt... All top shelf components...
Sometimes when I drop the BCG on the first round from the mag and squeeze the trigger, I hear and feel the "click" from the trigger.
Trigger is a new TriggerTech Diamond AR10 trigger. I eject the round, put it back in the mag...do it all over again and it fires fine. It doesn't always do it and may do it on the 3rd or 5th round. Intermittent.

I'm trying to figure out where to focus on. Spotlessly clean the bolt and carrier, etc..... Still intermittent. Hand loads..... Lapua brass, Federal match primers....

Any suggestions would be appreciated.

While I am pretty sure you have the TT AR10 Diamond trigger is installed 100%, make sure your set-screws at the back are fully seated. One thing I did for my AR15 TT Diamond in my 300BLK was to increase the trigger pull weight by 2 clicks from where I had originally set it. It's probably at about 2 lbs or so now. When I took it to the range the last time, I had a few hiccups that induced my 2-clicks UP in weight.

I have a TT AR10 Diamond in my 8.6BLK SBR, but haven't taken it to the range yet so I can't say if I have experienced the same situation as you. That said, again...make sure the two set-screws are fully seated, so that the hammer is fully striking the primer.

 

[bigjake83]

I damn near exclusively run TT now, the hammer springs are retardedly over powered. If you're getting failures to fire/ light strikes it's not the trigger.

Inspect your Bolt and firing pin, look to see if your firing pin has proper protrusion, clean your Bolt and Carrier inside and out then check headspace.

Also as mentioned above check for proper installation.

 

[hlee]

Money says the carrier isn’t fully forward, but forward enough to allow the trigger to drop.

 

[USK308]

Money says the carrier isn’t fully forward, but forward enough to allow the trigger to drop.

of course, there is that too! OP...is your BCG lubed up to be sloppy wet?? LFAR's (Large Frame ARs) are notorious for needing to be pretty well lubed to ensure good functionality.

 

[Thumper580]

Are you 100% sure that the bolt carrier is going all the way forward?

Yep, I put in a 10oz. buffer and a Wolff spring from Slashes Heavy Buffers for more dwell time. It's the smoothest engaging bolt I've ever felt/seen.

 

[Thumper580]

I damn near exclusively run TT now, the hammer springs are retardedly over powered. If you're getting failures to fire/ light strikes it's not the trigger.

Inspect your Bolt and firing pin, look to see if your firing pin has proper protrusion, clean your Bolt and Carrier inside and out then check headspace.

Also as mentioned above check for proper installation.

I meticulously clean the bolt and carrier every time I shoot it. I've pushed the firing pin forward with my finger to make sure it protrudes... It does. The JP bolt was headspaced when the barrel was machined by Craddock Precision.

 

[Thumper580]

of course, there is that too! OP...is your BCG lubed up to be sloppy wet?? LFAR's (Large Frame ARs) are notorious for needing to be pretty well lubed to ensure good functionality.

Yep, I'm OCD on making sure it's well lubed.

 

[srt-4_uk]

Lapua brass new or once fired?
You using a small base die?
When it doesn't fire, is it hard to pull the charging handle?

 

[Thumper580]

Hey guys, thanks for the responses. I'll check everything mentioned above.
I'm beginning to think it's possible with the heavier buffer and stronger spring there might be the possibility that the BCG may be experiencing ever so slight "bounce back"..... Maybe just unlocking enough to let the firing pin drop by not fully in to get a full primer strike..... Just my theory.... I'll test this by manually verifying the BCG is fully locked. Thanks.

 

[Thumper580]

Lapua brass new or once fired?
You using a small base die?
When it doesn't fire, is it hard to pull the charging handle?

New Lapua brass, regular FL Redding type S die. The unfired cartridge comes out super easy.... No drag at all.

 

[bfoosh006]

No offense intended, but are your primers are fully seated ?

 

[Thumper580]

No offense intended, but are your primers are fully seated ?

Yes, just below the case rim. You can feel the primer slightly deeper when you run your finger over it... and see it as well.

 

[Chickentoast]

I would try a taller shellholder in your press. I had a similar issue - rifle was not quite going into battery because the shoulder on the brass was a couple thou too tall (new starline). So close that I couldn't tell by eye or feel.

 

[Cascade Hemi]

Sounds like a magazine or feed ramp issue.

 

[camotoe]

Are you over sizing the brass,?

 

[Thumper580]

Are you over sizing the brass,?

Don't think so. Pushing the shoulder to 1.620... The sized brass is checked in a case gauge and looks perfect.

 

[Chickentoast]

Don't think so. Pushing the shoulder to 1.620... The sized brass is checked in a case gauge and looks perfect.

Push one back a bit further and see if it makes a difference.

 

[DocRDS]

Yes, just below the case rim. You can feel the primer slightly deeper when you run your finger over it... and see it as well.

Don't feel. Measure. I have a terrible time with Magnum Primers and I thought I "felt" them all low.
Measure
Measure
Measure
Couple thousand rounds LRP: No issue
1/5 Magnum rounds w Mag primer: "CLICK" I even thought I squeezed all the way down on my primer seating. Nope still had more to go.

Does this happen with other rounds or just the first. If other rounds: Suspect ammo.
1st only: Suspect rifle.

Good luck.

Also if you have another 308, see if the problem replicates there with the same ammo (aka test the ammo separate from the gun, or try a box of factory in your AR-10).

 

[BCP]

If it's a good strike on the primer then I'd think bad primers, if it's a light dimple then your firing pin isn't falling all the way maybe not in battery. Of course you could stick a regular milspec crap trigger in there for testing issues too.

 

[hlee]

That the reported issue arrises on the first round, when the op drops the bolt manually, would seem to point to the rifle. Of course, it is possible that the observations are not 100% accurate.

Has the OP done any additional testing?

@Thumper580

 

[Thumper580]

That the reported issue arrises on the first round, when the op drops the bolt manually, would seem to point to the rifle. Of course, it is possible that the observations are not 100% accurate.

Has the OP done any additional testing?

@Thumper580

It can happen on the other rounds besides the first one..... It's random.

 

[Cascade Hemi]

Post a picture of the feed ramps and a picture at the chamber of a loaded magazine inserted.