Phantom jam AR15

[Dr.Rob]

Had a jam at a match today where my bolt went back and would not come forward, charging handle wouldn't release it. Percussive maintenance (quick rap to the side of the stock) shot the bolt home, I fired a few more rounds without trouble but I timed out of my stage.

Back at the bench, went to work the bolt and it stuck half way open.

Field stripped it, didn't see anything obvious, lubed it and finished the match.

Hoser suggested a weak buffer detent spring, or a sheared hammer pin.

Detail stripped and cleaned.. nothing amiss except a chip on the buffer tube?? The stock had a tiny bit of wobble, I turned the tube about a 1/16 of a turn and tightened the stock screw tight as it would go.

Nothing looks obviously broken. Can see where it bound up but not why. Clearly the carrier hung up on something.. no debris, no blown primers. No springs bent or damaged that I can see.

Could it be I just need new springs?

PS the bright sots on the top of the lower were there previously, the new marks are on the lower just above the rear take down pin.

 

[taliv]

some things to check...

there is a hole in the rear of the receiver extension (buffer tube). make sure it's not plugged up with grease or dirt or something
the wobble could have done it if it misaligned the carrier enough so that it hung on something
a popped primer can wander around and get into places that cause something like this. it may have fallen out or it may still be hiding around your trigger or something
also, make sure you are using the correct length buffer and spring.
action spring (buffer spring) is a wear item. typically, you replace them once they are too short. there's like a min length for them. i forget what it is but should be easy to look up. prob a good idea to make a gauge by marking your rifle case or somewhere so you can check your spring when you do maintenance. if you happen to have a spare new one, you could just compare the two and if the current one is a good bit shorter, discard it. they're only like $3 anyway.

 

[Dr.Rob]

I'm probably overgassed for a rifle length tube I'll see if I can find the measurement spec.

 

[Dr.Rob]

AHA! mil spec is 12.75, mine has compressed to 11.75!

44 coils in all, spring is not straight, bowed to one side.

Time for a new one of those!

Guess I'm shooting enough to wear stuff out!

 

[Hardtarget]

If you're shooting enough to wear out the spring, well...that's a good thing! I hope you've found the problem. Just wondering, is that your Model1sales rifle? I'm thinking I remember you having one from those guys. I have one of their rifles...love it and it shoots good, too!

Mark

 

[taliv]

https://www.thehighroad.org/index.php?threads/diagnose-ar-malfunction.412388/#post-5147731

 

[Dr.Rob]

Yeah it's my Model One 16 inch 'varminter' which makes a great competition gun.

 

[Dr.Rob]

Thanks Taliv I made that mistake once while swapping stock, this rifle has been trouble free for a long time. New springs on order. Hope that fixes it.

 

[Robert]

Wish I could have been there. I had a wicked chest cold and felt like poo. I'm glad you figured it out. I'll be there to lose to you next month.

 

[Dr.Rob]

That chest cold happen up in Chaffee County?

I came in 15 out of 23, that jam wasn't my only issue but I burned 30 seconds or more on it.

I was breathing harder than I should have on stages one and two. I had to chase the final plate on the star for a few extra rounds and cleared the dueling tree easily. I was struggling to keep a steady sight picture. On stage two it seemed to get worse. I was winging shots rather than calling shots then I jammed up and got one more round off before I timed out. Ugh. Remarkably, I settled down a lot on standards. Noticed I was rushing a bit there too.

My leave of absence from roller derby has turned into extra pounds and a lack of cardio fitness. Time to get back on the bike and treadmill.

I still out-shot everyone that stayed home.

PS you missed a guy running a G3 with irons and period flecktarn kit.

 

[bfoosh006]

I am thinking your wobbly stock may have allowed the buffer detent to move up and in the way of the BCG.

Your tightening of the stock would have "engaged" the buffer detent properly.

 

[Dr.Rob]

Well, there's your problem...

New spring vs. old.

 

[taliv]

is it running well again?

on a slight tangent, i think a lot of the guys that do the "shoot 100 rounds and call it good" thing with their rifles, then squirrel 100,000 rounds away in their basement for the post-apocalyptic scenario of their choice, probably never realize that there are a lot of wear parts on rifles. 10 years ago, there was a huge difference in quality that often correlated to brand, and all the chart drama etc. doesn't seem so bad these days, but even so... I'd really recommend searching THR and M4C and arfcom for the spare parts kits threads and grabbing a small fishing tackle box and spending a few bucks on things like extractors, springs, rings, etc.

 

[jmorris]

When it comes down to it, it doesn't take much to cause failure of things. A fuse and your car is dead, an o-ring and Astronauts and millions of dollars are gone, a speck of debris (maybe buffer tube in this case) in the wrong spot and your rifle malfunctions, a rap on the stock and it's running again is a pretty easy fix.

How

 

[taliv]

very true. i keep a large bag of all the spare fuses in my truck (which i tend to use way too often), and extra orings for my space shuttle. so totally makes sense to do same for my guns

 

[Dr.Rob]

I ordered extras. Rifle and carbine sized, clearly labeled. Old spring is in the trash.

I am going to miss tomorrow's tactical rifle match but I am going to run up to Chaffee county's range this week and see how it works out.

 

[Walkalong]

My FJ's fuse holder has space for spares. I keep it full. It saved my bacon once. My dad used to keep a set of old radiator hoses and belts in the trunk. I keep a nice set of jumper cables in the back, they got me home once when my last battery died at 2:00 in the AM trying to leave work after coming in on call, and has jumped off countless strangers.

I keep extra AR parts. A full LPK, extra complete bolt. I don't run them hard like you guys who play the gun games though.

 

[chicharrones]

Well, if y'all bring up spares like fuses and such, I keep a set of spare capacitors for my house's a/c compressor unit. I seem to replace them every other year when one dies.

I have extra recoil springs for some of my handguns, I guess I ought to keep a few spares of some things for my rifles as well. The AR would be a natural choice for that considering how simple it is to replace some of the parts.