Tips for correcting rampant bump/burst firing w/ RA140 trigger?

[Arakisk]

PCC has Taccom bolt/buffer totalling at 20.6 oz cyclic mass. 12.5" Brekke barrel/comp/handguard, Rise Armament Rave140 trigger, using factory 115gr ammo from various companies. Have tried BOTH 223 carbine and 308 carbine springs. Total gun weight is 5.75 lbs at the moment, and it is short stroked so that the bolt stops at the rear top edge of the ejector.

In both cases, I have gotten bumpfire intermittently, with the 308 spring actually causing bumpfire almost immediately upon first usage. I have tried gripping the gun harder. I have neverr had a bumpfire in 5900 rounds of the same ammo prior to installing the Brekke barrel/handguard, which removed approximately 0.75 lbs compared to the intial setup. The trigger was also replaced under warranty maybe 200 rounds before the other parts being swapped.

Any tips for correcting the issue? I have had people suggest using a 308 rifle spring, a possible defective trigger, or a lighter 223 carbine spring. My last-ditch solution would be to simply increase the mass of the gun in the buttstock area to reduce the shake of the firearm. I took the gun out today and got a burst of 3-4 rounds immediately upon trying to zero the gun from kneeling with factory ammo and the 308 spring. I also experienced one failure to reset with the RA140 trigger today.

Edited February 25, 2021 by Arakisk

[Ner]

You may check the firing pin spring. I had a massive slamfire problems because of that. It was compressed + the large amount of shortstroke made this thing cycle 

[Arakisk]

8 hours ago, Ner said:

You may check the firing pin spring. I had a massive slamfire problems because of that. It was compressed + the large amount of shortstroke made this thing cycle 

I checked the spring and it doesn't seem unusually compressed. The firing pin is titanium, and still intact.

[MoRivera]

I had similar things happen with an RA140 trigger.  Turned out that the disconnector spring had compressed and was basically ineffective, so the disconnector wasn't catching the hammer after cycling.  I replaced it with one from a mil spec trigger group, having to put the tapered end down to fit in the bottom hole but it functioned fine and has been normal since.

[Arakisk]

On 2/27/2021 at 8:10 PM, MoRivera said:

I had similar things happen with an RA140 trigger.  Turned out that the disconnector spring had compressed and was basically ineffective, so the disconnector wasn't catching the hammer after cycling.  I replaced it with one from a mil spec trigger group, having to put the tapered end down to fit in the bottom hole but it functioned fine and has been normal since.

Yes, I have just now recently determined that the trigger was likely the issue. With the lower separated from the upper, I pulled the trigger, recocked the hammer while holding the trigger back, and then quickly released my thumb from the hammer. The hammer was able to override the disconnector and "fire".

[robertg5322]

I have two of their triggers, both had issues. Had to change the disconnector springs, and adjust the set screw at the front of the trigger assembly, not impressed. Sad because other than the hammer follow, they were nice triggers...

 

Won't be wasting my time on their product anymore, CMC PCC trigger isn't that much more expensive, and I've had zero issues with their products.

[Arakisk]

On 3/4/2021 at 6:54 PM, robertg5322 said:

I have two of their triggers, both had issues. Had to change the disconnector springs, and adjust the set screw at the front of the trigger assembly, not impressed. Sad because other than the hammer follow, they were nice triggers...

 

Won't be wasting my time on their product anymore, CMC PCC trigger isn't that much more expensive, and I've had zero issues with their products.

I have noticed that the overtravel on a CMC 9mm trigger is a bit longer than the RA140 i came from. Is that also your experience?

[ltdmstr]

I've been using the CMC PCC trigger for about a year.  It's nice and crisp and so far 100% reliable.  It's not the lightest, but I really don't need a pound and a-half or two pound trigger on a PCC.

[robertg5322]

On 3/7/2021 at 8:38 PM, Arakisk said:

I have noticed that the overtravel on a CMC 9mm trigger is a bit longer than the RA140 i came from. Is that also your experience?

I only have one CMC trigger, in a regular AR (not a PCC), and it has about the shortest travel you could expect. I have no issues at all with it. 

 

I don't own a CMC PCC trigger, but if I were in the market for a PCC trigger, it'd be an option, mostly due to the price being reasonable.

 

I have one JP Trigger (just the trigger & disconnector kit), and it works nice. A little heavier than I'd like, but ridiculously short reset, no pre or over travel. Not bad at all for what it is. Only cost $90.00. 

[MoRivera]

On 3/1/2021 at 1:10 PM, Arakisk said:

Yes, I have just now recently determined that the trigger was likely the issue. With the lower separated from the upper, I pulled the trigger, recocked the hammer while holding the trigger back, and then quickly released my thumb from the hammer. The hammer was able to override the disconnector and "fire".

Yeah, sounds like what was happening with mine.  The spring for the disconnector was incredibly stiff out of the box, as if it wouldn't compress at all.  So consequently firing/cycling would feel like a jackhammer slapping back on your finger, you could feel the hammer just struggling to put the disconnector back just to hook it.  You just couldn't move that 'hook' back at all.  But after about 200-300 rounds it began to soften and then you could barely feel or hear the 'click' as it engaged the disconnector upon dry cycling.  And that's when I got a six-round burst at the range then recreated it on the next shot.  So I think it just bound down and flattened this spring, or it was like the spring was already completely compressed before and this just crushed it. 

Edited March 12, 2021 by MoRivera