I have an AR that is short stroking.  It will never lock back after the last shot, and it occassionally fails to pick up a new round from the magazine.

I've read that the gas rings on the bolt can wear out, so I'd like to replace those first since they're so inexpensive.

Would someone kindly point me to instructions on dissasembling the bolt carrier. I searched the AR board but didn't find anything in the last 30 days.

Pull the firing pin retainer which is the little "cotter pin" that holds the firing pin in place.  You may have to push it out partly from one side, the when the head is exposed, pull out and set aside.  Now, with the bolt up, shake out the firing pin.  Push the bolt all the way into the carrier, and twist the cam pin 90 degrees.  (The cam pin rides in a diagonal slot under the carrier key)  The cam pin cannot turn with the firing pin installed, as the firing pin goes through a hole in the cam ping.  With the bolt pushed back into the carrier, and after twisting the the cam pin may be removed.  It will just barely slide past the carrier key.  (The carrier key is the part that engages with the gas tube in the upper receiver.)  Now the bolt can be pulled out.  On the rear of the bolt you will find the gas rings.  Pry one end up and over the lip of the end of the bolt.  Work around the ring and push it over the lip all the way around.  Do the same with the other two rings.  Clean everything well, and reassemble.

You may want to consider the one-piece spiral McFarland ring.  A number of manufacturers are using them now, incl Armalite.  I have them in most of my AR's.

Just to add, when you have the carrier in hand, check the key allen head screws.

If the screws are loose (not set to 35lbs), then gas can leak out between the key and carrier and cause short stroking.  If the key is tight, and the new rings do not solve the problem, then take a look at your hammer/disconnector tail . It may be that the hammer tail is too long and is binding up the carrier on the way back.  The tell tale sign is a wear mark just behind the disconnector hook at the back of the trigger. If you have the dent/line, then grind .040 off the hammer tail where it contacts the disconnector tail behind the sear hook.

Hope this helps.

Thanks!

I actually suspected that the removing the firing pin was the key to the whole thing.   The carrier key screws are staked, so even though that looked like the obvious way to get the cam pin out I knew that couldn't be it.

Thanks for the disconnector tail tip, that might just be it because this AR had a (butchered/worn out) trigger group when I got it (it was firing multiple times per trigger pull, there was little finish left on the parts and I suspect some idiot had been filing on the sear surfaces) so it has a new trigger.  I only fired a half a magazine through it before I replaced the lower assembly parts, so I don't know if it was short stroking before or not.

[b] Take a peek at this [url=http://www.ar15.com/content/parts/boltcarrier.html] B&C [/url]

[url=http://www.ar15.com/content/parts/bolt.html]Bolt[/url]
[url=http://www.ar15.com/content/parts/carrier.html]Key&Carrier[/url]


Good luck

Dano, I think you hit the nail on the head.

I just took these pics:

[img]http://www.fastclan.com/members/griz/tail1.jpg[/img]

[img]http://www.fastclan.com/members/griz/tail2.jpg[/img]

That was a brand new disconnector about 500 rounds ago.  I compared it with a disconnector out of another AR that has about 10,000 rounds through it, and there isn't so much as a scratch at that spot.

[red]GOOD CALL DANO!!!![/red]

Dano is right about the long hammer tail, and this is VERY common.

I'm not sure how long you have had your AR15, but if you have had it that long, you may want to learn how to take the bolt out of the BC if for no other reason than to clean it.

I know how to now, but I don't see any reason to do it very often.  If it can go 10,000 rounds without a single malfunction with just being wiped down and lightly lubed every thousand rounds or so, it must not [i]need[/i] to be totally taken down for cleaning very often [:D]