FTF's possible buffer spring issue?

[Alaskagrown]

So here is my set-up:
LMT 16" upper
BCM FA BCG

Double Star Lower
DPMS LPK
BCM Mil-Spec Buttstock with BCM stock buffer spring
Carbine and H Buffers

Running a YHM Phantom suppressor

Mags
P-Mag
old O-Kay with black follower
Brownells with green follower
C-Products with grey Magpul followers

my problem is the gun has never run 100% for more than one mag thought it might be mag related because I only had old mag and suspect C product mags so I bought the Brownells and Magpul mags. Yesterday I took it to the range P-mag functioned 100% brownells mag failed to chamber round when I released bolt on a loaded mag (28 rounds loaded) looked the nose of the round stopped on feedramps. Pulled Ch and let it slam home 4 more shots and bolt hung up on the same spot seemed like every 4 rounds it would hang up. Finished that mag using CH every 4 rounds. Switched to C-Products same thing failed to chamber on loaded mag FTF every 4 rounds switched to H Buffer thinking added weight might assist it didn't every 2-3 rounds FTF however bolt would be closer to closed.
Switched to P-mag same issues as previous 2 mags. Halfway through P-Mag gave up figured it wasn't mag related.

I am thinking that the buffer spring is the culprit since the bolt didn't have enough force to chamber rounds on loaded mags. At least once I dropped a half loaded mag and then re inserted the mag and it still wouldn't chamber.

Anything I am overlooking or should check first or does it sound like a buffer spring to everyone else?

[Thomas M-4]

What ammo were you using?
Also have you measured the buffer spring what length is it?

[Alaskagrown]

ammo was Winchester 223.

I will check buffer spring lenngth when I get home.

I wouldn't think ammo choice would cause the bolt to not chamber the round when hitting the bolt release on a fresh mag.

[Alaskagrown]

buffer spring is 10 inches at most

[spamsammich]

If it is under 10 inches, that is too short. Carbine springs range 10-1/16" to 11.25".

[Quib]

buffer spring is 10 inches at most

Scroll down to my diagram with buffer spring lengths.

http://http://www.weaponevolution.com/forum/showthread.php?t=1613 (http://www.weaponevolution.com/forum/showthread.php?t=1613)

I had a similar situation with a new LMT SOPMOD stock I installed. The buffer spring was too short, and simply lacked the power to push the bolt and carrier forward with enough force to strip a round from the mag. I replaced the spring and cleared the fault.

[Thomas M-4]

Yea 10'' is to short I replaced mine when it hit 10 1/8''.
Quib's link is a good one follow it.
I always post the ammo We don't know it could be uncle Bobs not sized correctly reloads but it does sound like the buffer spring is to short and needs replacement.

[Heavy Metal]

Sharp edges on the corners of the Reciever Extension cut-outs for the bottom two bolt lugs (the ones at teh top of the feed ramps) can also cause problems.

I have seen cheap barrels that would snag the noses of the bullets here.

[Bucks13]

Sharp edges on the corners of the Reciever Extension cut-outs for the bottom two bolt lugs (the ones at teh top of the feed ramps) can also cause problems.

I have seen cheap barrels that would snag the noses of the bullets here.

I may have this problem you speak of...is it ok to take a file to the lugs and round them out a bit? Would I need to worry about premature wear/failure/rust if I do file them?
Thanks for your help ahead of time.

[Quib]

I may have this problem you speak of...is it ok to take a file to the lugs and round them out a bit? Would I need to worry about premature wear/failure/rust if I do file them?
Thanks for your help ahead of time.

I’ve never had a reason to, so I’ve never personally performed this, but I have seen it recommended in the past to take a piece of crocus or emory cloth and wrap it around a small wooden dowel. Use this to knock down the sharp edges on the feed ramps. I think a file might be too extreme.

[Heavy Metal]

I have broke corners with a small flat Jeweller's File and then polished the area with a Dremel and a Felt Bob using JB Bore Paste.

In fact, I do it as a matter of routine on a new barrel install for insurance. Cleaning the stray JB out of the barrel extension is the biggest hassle.

It can be done with the barrel in the reciever but it is easier to do with it out of the upper.

It is hard to over-do-it with such limited tools.

[Heavy Metal]

I may have this problem you speak of...is it ok to take a file to the lugs and round them out a bit? Would I need to worry about premature wear/failure/rust if I do file them?
Thanks for your help ahead of time.

It will not cause any wear issues. In fact, as far as rust goes, I have even polished the entire feed ramps at the same time. If you are lubing your rifle anywhere near enough, this area will stay so wet rust is a non-issue. If your polished ramps are rusting you are doing somethign seriously foobar with your bolt lubing.

[Quib]

I have broke corners with a small flat Jeweller's File and then polished the area with a Dremel and a Felt Bob using JB Bore Paste.

In fact, I do it as a matter of routine on a new barrel install for insurance. Cleaning the stray JB out of the barrel extension is the biggest hassle.

It can be done with the barrel in the reciever but it is easier to do with it out of the upper.

It is hard to over-do-it with such limited tools.

I can see using a small jewelers file.

But on the other hand, I can just imagine someone going to town on their new barrels feed ramps with a rat tail file! LOL.....:o

ETA: Remember the DIY Dremel fluted barrel?

[Heavy Metal]

ETA: Remember the DIY Dremel fluted barrel?

Just because someone can do something does not mean they should do it.

[Bucks13]

thanks for the replies guys. i think i'll go ahead and give it a go.

oh, and i should have clarified....i didn't actually mean i would use a file, i was planning on using a 220 grit filing stone i got from my die maintenance guys at work. thin, flat, hard so it won't flex and very fine.

do you think compressed air and some CLP will be enough to get the dust out of the barrel extension when i'm done?

[Heavy Metal]

Remember, you are trying to break the corners on the bottom two cut-outs on the star-shaped hole in the extension, not the ramp itself but the clearace cut for the two lugs at the top edge of the feed ramps. It will have to be considerably thinner than a bolt lug to work. You are trying to give it an angle. A Jewelers file is very thin and flexes a bit. It is ideal for this. You can even get diamond dust Jewelers files that work work even better. Harbor Frieght sells both.

The cut out is shaped like a boxy 'U'. I try and break the edges on all three sides.

As to any debris, I would hose it with brake-cleaner and flush it out the muzzle and throughly re-lube.

[Bucks13]

Remember, you are trying to break the corners on the bottom two cut-outs on the star-shaped hole in the extension, not the ramp itself but the clearace cut for the two lugs at the top edge of the feed ramps. It will have to be considerably thinner than a bolt lug to work. You are trying to give it an angle. A Jewelers file is very thin and flexes a bit. It is ideal for this. You can even get diamond dust Jewelers files that work work even better. Harbor Frieght sells both.

The cut out is shaped like a boxy 'U'. I try and break the edges on all three sides.

As to any debris, I would hose it with brake-cleaner and flush it out the muzzle and throughly re-lube.

Thanks. I know exactly where you're talking about, so I should be good to go. And the stone I have is 1.67 mm thick and just under 13 mm wide, so I'll be able to do some detailed work.