View Full Version : AR-15 bolt won't even manually cycle

March 11, 2012, 09:41 PM
I just put together my new AR and am having a small problem. Well... maybe it is a big problem.
When I pull the charge handle, it won't come all the way back. In fact, it only comes about halfway back (not far enough to chamber a shell) before it feels like it binds up. It seems to me like the bolt is dragging in the tube.
I am using a DPMS colapsable stock and various other mix and match parts.
I had a buddy try the upper on one of his lowers and it worked so I am not sure where the problem is. Unfortunately I haven't had the chance to try another upper on my lower yet.
Any ideas?
I am relatively ignorant in the ways of black rifles so no suggestion is to silly.

March 11, 2012, 09:46 PM
Forget to put in the buffer/spring? (I've done that is only why I ask :o) Full length buffer in carbine length tube? Bent tube?

March 11, 2012, 11:18 PM
So, I have a little more info...
I removed the rear takedown pin and held the upper and lower together while I pulled back on the bolt. The bolt will go all the way back and lock like this but it has to push the upper and lower a little appart which causes the rear takedown pin hole to be sightly misaligned.
My new theory is that the bottom of the bolt is hitting inside of the tube and is binding up.
What are my options to remedy this? Is it an equipment problem or a me problem?

March 11, 2012, 11:22 PM
Can you compare your lower to your buddy's? Do all of the corresponding parts between the two lowers appear to be in the same position and orientation?

March 12, 2012, 06:27 PM
Aren't there "big pin" rifles and "small pin" rifles? I don't know a dang thing about AR's but I just recently read something about this.


March 12, 2012, 07:27 PM
is you buffer detent down far enough?

March 12, 2012, 08:23 PM
Is the hammer cocked with safe on?

March 12, 2012, 09:17 PM
Second on the buffer detent causing your problem. You have to screw in the stock far enough that it catches on the lip of the pin and keep it down, but not too far so it binds.

March 12, 2012, 11:00 PM
I don't have a lower immediately available to compare to this one.
I checked the detent and it appears to be working correctly. The stock is riding over the shoulder of the detent with the center sticking up. I can push back on the buffer and push the detent down and it springs back up into place. I think this means that the buffer detent is not binding on the stock.

March 13, 2012, 04:10 AM
would probably suspect bent buffer tube also, might take out the spring and buffer and look inside the tube to see what it looks like before trying another tube.

March 13, 2012, 08:09 AM
I can see where the bolt has been rubbing on the inside of the buffer tube. I assume that is one of the signs I should be looking for. Can I get a new buffer tube or do I have to buy a whole new buttstock assembly to get a new tube?

March 13, 2012, 08:19 AM
I answered my own stupid question. I will see if I can round up a different stock to try. If not I will order a new tube and try that.

March 13, 2012, 10:02 PM
So I besically narrowed it down to something being wrong with the way my upper is alligned. I tried the upper on two other good lowers and it would not function. I tried my lower on two other uppers and it worked just fine. So I may try and find a stripped upper and have it swapped into the assembly I have. Thanks for the input.

March 14, 2012, 05:22 PM
You have narrowed it to the upper assy.Try your upper on your buddy's lower,but switch bolt carrier groups.If the different bolt carrier works,look close to see if the staking of the top screws has pushed some metal up that is dragging.If so,dress it off flat.

Try swapping charging handles. Look real close at your forward assist to see it is fully retracted.

You will get it.

I think probably ,unless you bought some super cheap knock off parts,the upper and lower receivers will be to spec.If it is a carbine stock,you need a carbine length buffer and spring.

What stock and tube are you using?
What stocks and tubes were on the alternate lowers?

Take your upper assy off,pull the bcg out .Look at how the gas tube lays in the upper.Is it centered?The one place you can mess up an "alignment" is by not aligning the hole for the gas tube when tightening the barrel.

Another possibility,were you using proper tools or make do tools when holding the receiver during barrel nut torquing,etc?Any oppurtunities to crush,twist or otherwise distort the receiver?Is this a surplus parts kit ?

March 14, 2012, 05:42 PM
Sounds like something is bottoming out or a bent buffer tube. Make sure the buffer stop screw is threaded in far enough so threads of the the plunger are not exposed. Wiggle the stock while trying the charging handle,,,unloaded chamber & no mag of course,,,,?

March 14, 2012, 08:04 PM
Aren't there "big pin" rifles and "small pin" rifles?

yes you are correct