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yggorf
December 7, 2009, 08:10 PM
My normally reliable AR has started having a strange chambering problem -- or I should say "failure to chamber" problem. With no magazine in the gun, the charging handle and carrier/bolt seem to operate normally -- I can even get the bolt into battery with only a half-draw on the charging handle (pulling the bolt only halfway back). But, with a magazine with wounds in the gun, the carrier doesn't seem to have enough oompf to get into battery -- it ends up sticking almost closed. Sometimes a round is chambered but the bolt stays slightly open, sometimes the round is left at an angle trying to feed up into the chamber and the bolt overrides it - leading to a jam.

Do I need a stronger buffer spring?

shooter_from_show-me
December 7, 2009, 08:41 PM
You could try the Tubbs chrome silicon recoil spring from Brownell's site. Alot of guys recommend them and run them. Like any other part, a buffer spring is only good for so many cycles before it starts weakening.

Rottweiler
December 8, 2009, 08:26 AM
Tried a different mag?

NSO_w/_SIG
December 8, 2009, 09:16 AM
First factor you should eliminate is the mag, does it do this with every magazine?

LongRifles, Inc.
December 8, 2009, 09:30 AM
Make sure your not riding the charging handle forward. Pull and release.

Beg, borrow, acquire a magazine known to work and then check feeding. Ensure your ammunition is up to snuff also.

The factory buffer spring has more than enough stored energy to cycle the action properly. No need for "widget" parts.

If you decide to replace the buffer spring, replace the hammer spring at the same time. Both have about the same service life.

Good luck.

rocket12
December 8, 2009, 09:44 AM
handloads or factory rounds???? sounds more like ammo problem

Joat
December 8, 2009, 11:14 AM
If you have been using lacquered or plated steel case ammo, clean the chamber and try a known to work magazine. Rule those out before swapping parts.

Joat

yggorf
December 8, 2009, 11:19 AM
I tried several mags, some brand new and others known to work previously (even in the same gun), and the problem occurs with all of them.

The problem occurs with a number of different types of factory ammo.

I checked the staking of the gas key, and it looks fine.

The buffer spring does have about 4000 rounds on it, but I would have expected it to go longer.

Another possible factor is the weather - it has been about 30 degrees lately so maybe the oil is a bit thicker?

Transbrake
December 8, 2009, 05:20 PM
what brand is the ar? I know a few people that bought the S and W's and have had similar problems.

mapsjanhere
December 8, 2009, 05:49 PM
I'd second the "dirty chamber" guess, if you use up a lot of energy pulling brass out of a sticky chamber your bolt might not have the energy to cycle fully. Good cleaning and lubrication might do the trick, can even check the gun with a drop of oil on the cartridges first to see if it makes a difference.

yggorf
December 8, 2009, 07:16 PM
Still trying to locate the cause, I swapped out a bolt, carrier, and charging handle from another rifle and they work flawlessly. So I assume this has to be something on the bolt, carrier, or charging handle. In examining those pieces though, everything looks perfect. I cannot see any roughness, wear, or problem with any of them. By hand (not under gas pressure) they go in and operate smoothly. The only thing I noticed, which I don't believe could be the problem, is the firing pin retaining cotter pin had backed out a slight bit. These guys move around routinely though so I can't think that is it.