Sticky firing pin on AR question

[BigWave]

Was out coyote calling yesterday and had a double come in close. Set up to shoot the first and "click", no fire. Jacked andother and the same happened. Did that 4 times before the dogs ran off. Quit for the day and on the way home went to my shooting spot and could only get it to fire one time. Went home and dissasembled and cleaned the bolt/pin. It was slightly dirty, but by no means filthy. Reassembled and went out to test fire it again and it fired with no problems at all.
Is this normal. I had maybe 40-50 rds thru it since last cleaning. This is an RRA Predator Pursuit upper in 223.
Any help or thoughts would be appreciated.

Thanks,
Dave

[Gunsrruss]

Clean

When you clean the rifle make sure you run a pipe cleaner with hopes or your favorite cleaner down through the bolt. also use Q tips on the carrier and bolt to clean all areas. Have a nice day....

[scotthmt]

that sounds odd, what trigger are you using? are you sure its installed correctly. OH yeah, get pics of the coyote shooting!

[aplinker]

NOT normal.

There's no way you could gum up the firing pin that much.

+1 to scott's questions.

[Creampuff]

Did you save the casings? Are you getting soft hammer strikes?

[BigWave]

that sounds odd, what trigger are you using? are you sure its installed correctly. OH yeah, get pics of the coyote shooting!

Yeah, I thought it was a bit strange also. Last time out it worked great. I have a Timney 3# trigger in it and double checked the assembly. Everything is tight and functions perfectly. I cant imagine after just 40-50 rds that it would gunk up enough to stick the firng pin.

Just saw the other posts.

Forgot to mention that all of the cartridges had soft hammer stikes on the primer. Any more ideas?

Thanks guys!

[rayra]

what about carbon buildup on the back of the bolt behind the gas rings?
what about carbon buildup on the adjacent portion of the bolt carrier, down at the bottom of the bolt recess? Either of these can lead to the bolt carrier (and thus the firing pin) being held rearward enough to cause light strikes.

Very easy to gum the weapon up with only 40-50rds, with dirty powder, poor cleaning, heavy oiling. Need to clear ALL the firing pin channels / holes, not just the one in the bolt face.

[Boots]

I'm with Rayra, check anything and everthing that comes in contact with the firing pin. You'd be surprised with what a little bit of fud can do. Also, everytime I use Q-Tips, I always double check to make sure no fibers got left behind.

[aplinker]

Yeah, I thought it was a bit strange also. Last time out it worked great. I have a Timney 3# trigger in it and double checked the assembly. Everything is tight and functions perfectly. I cant imagine after just 40-50 rds that it would gunk up enough to stick the firng pin.

Just saw the other posts.

Forgot to mention that all of the cartridges had soft hammer stikes on the primer. Any more ideas?

Thanks guys!

Timney triggers have lightened hammer springs, which can lead to light primer strikes and easier fouling of the firing pin.

I've had gummed/glued up firing pins shot through thousands of rounds that should have stopped but don't with a stock hammer.

[jgraham15]

I had this issue once with the Timney 3lb trigger module I have installed in my girlfriends AR. I guess I got a little too much lube on the firing pin and after 30-40 rounds It gummed up enough to keep the gun from firing. I cleaned the lube out of the inside of the bolt and off of the firing pin and it worked fine again. I did some research and found it is a problem with the light spring in the 3lb module. I hear you can call Timney and they will send you a new spring that is stronger (it was meant for the AR10 module) and it will stop the problem from happening. I just make sure that I don't over lube it anymore and I haven't had any problems since. I also installed 4lb trigger modules in my other AR's just to be safe!

[BigWave]

Thank you guys! I just had it apart again and cant see anything that would cause a problem. I think I will call Timney and talk to them about it like jgraham is saying.

[Francis Marion]

That's a problem consistent with a weak hammer spring.
Wouldn't hurt to replace it with a new, stiff spring.
Have a buddy with a properly working AR? Break open your rifle and his, and using your calibrated thumb, test how much force is required to cock the hammer. ARs with weak hammer springs are noticeably easier to cock compared side by side to a strong spring.
For additional confirmation, swap uppers and see if the problem follows your upper, or if the problem remains with your lower. Likely the prob is with your lower.

[arfan66]

Here's a thought.....

When you reassembled the bolt/bolt carrier assembly prior to the hunting trip did you install the firing pin retaining pin (cotter pin) in front of the firing pin's flange?

I've done it before and the problem won't show up while doing the post cleaning function check.

[ocabj]

I've done it before and the problem won't show up while doing the post cleaning function check.

Actually, it would. When you tilt the reassembled bolt carrier bolt face up, the firing pin would fall out. Also, when you push the bolt in so it's cammed back toward the bolt carrier, and you press the back of the firing pin to run it forward, you would see that the tip of the firing pin isn't protruding past the bolt face.

[BigWave]

Yep, cotter pin was in the correct position. While cleaning it a while back I did accidentally put it in wrong and I noticed it immediately but not this time. I cleaned it again and shot it again today. It performed perfectly through about 20 rounds, Cleaned it again when I got home. Who knows???