I am new to the AR-15 world, so I hope I am not asking stupid questions.

My rifle:
Rock River Lower
Del-Ton Mid-Length Upper
Wilson Chrome Lined Heavy Barrel in 5.56
Ammo:  Tulammo 55 gr steel cased
Magazines:  30 round gray metal mags with green follower from DPMS and 20 round Thermold mags made in NC

Problem:  I took the rifle out for the first time today.  First 5 rounds fired from 30 round mag fine.  Then "click".  Bolt did not chamber round.  Manual cycled and fired fine, then click on next round.  This happened repeatedly.  Tried a Thermold mag and all 20 rounds fired without incident.  Used another metal mag and it became a single-shot rifle again.  Changed to another Thermold and it would fire a couple of rounds then become a single-shot for the rest of the mag.  It happened like this with all 5 Thermolds and both DPMS mags.  Switched to a Stoner mag (buddies) and had same problem.

Took BCG out, stripped, cleaned.  Reassembled, fired 10 rounds from Thermold, no problem.  Then it started again with both metal mags and Thermold mags, just like before.

First thought, something is wrong in the BCG.  Put my buddies bolt in, fired 20 rounds no problem from Thermold, so I thought problem is bolt.  SO, I put my bolt back in and it fires 17 rounds fine from Thermold, but then goes to crap again.  Changed mags and went back to single-shot rifle.  I guess I should have fired more with buddis bolt in to be sure, but I was really aggravated at that point and he had to leave.  After he left I shot about 70 more rounds, basically all in single shot mode.  My hand really got tired pulling that charging handle so many times.  :)

I know some people say Tula ammo is no good, but know other guys who fired same ammo through the RRA lowers with delton uppers with nothing like this happening.

Assuming the ammo aint the problem, what should I look at first?

Thanks in advance!

Thanks for the help.

Read the FAQ in the Discussion Thread.

Sound like its Short Stroking.. try different ammo, make sure gas key isn't loose and properly staked. there are a few things can cause this problem...

Thanks for the replies.

Forgot to mention that I tried the "one round in mag" to see if bolt locks back on empty mag, and it performed properly with all magazines (7 total), so that does not sound like a short stroke to me, which is what I was starting to think it was.  The fact that it would cycle fine (albeit randomly) at times leads me to believe that it is not short stroking by definition.

I saved one round that got "passed over by the bolt" and you can see two small "dings" and a scratch the length of the casing whre the bolt hit it when passing over.  The mags were seated properly in the magwell.

Also, gas key is tight.

Maybe it's just the magazines, which by the way are brand new.  The two metal ones are NHMTG 30 rounders.  I took them apart and they appear to be brand new.  However, the rounds seem to fit really tight in the metal mags.  It is very difficult to strip rounds by hand.  Not sure if that is normal.

So, here's what I'm going to do (in order):
1.  Soak the BCG in lubricant ( I thought I did this, but maybe not enough).
2.  Check the gas block for misalignment and gas tube for crimps.  (it's brand new, and as it did fire through two full 20 round mags, I doubt it's obstructed)
3.  Try different ammo (although I don't see how this is the problem, as the rifle did have hiccups of succesful firings, see #2 above)
4.  Try some different mags and label current ones when testing (could be that the two that fired all 20 rounds properly are the only two good ones I have.)  
5.  Change to a shorter buffer spring.
6.  Take the lemon back to the gun store and pitch a fit. (there are probably other steps to try before this, but a new rifle shouldn't cost me too much money to fix...the gun store's gonna have to come off some parts).

Please comment on my comments, as I need all the help I can get here.

Hrmm...  

I experienced a similar problem not long ago.  

It ended up being my gas block.   I had a local gun shop install my free float rail (should of just done it myself) and they didn't tighten my gas block down.  

First outing it functioned fine.  

The second outing it short stroked almost every round.  

Third outing it was effectively a single shot rifle.  My gas bock had worked itself forward so NO gas was getting back to receiver.  

With that said... check your gas block.  



Also... if possible have a friend stand next to you and watch the bolt as you fire.   To rule out short stroking.  If you're getting full motion from your BCG then it's probably not a gas problem.  

didn't see this post below.

I would say first thing is to thoroughly clean and lube both your rifle (paying special attention to the chamber with a chamber brush and CLP and the bore with some sweet's solvent) and your mags (yes mags ... disassemble clean and lube them) even brand new factory mags can be very dry have dirt and debris in them not to mention what gets inside used mags. Also ... your not using your mag as hand hold are you? ... that can cause some problems.

I've never used steel cases but, from what I've heard and researched, a steel case doesn't expanded inside the chamber like brass does. From what I've been told... As a brass case is extracted from the chamber, the case is still expanded and pushing against the walls of the chamber. as the case is being ripped out, it is pulling some of the dirt and fowling along with it, thus slightly cleaning the chamber. A steel case will not do that. some of the "coating" on the case is left inside the chamber and when it gets hot it causes feeding/chambering/extracting problems.

Like I said, I've never used it, so somebody with more knowledge on that might chime in soon. Good Luck and get up and runnin' soon

Someone on another forum suggested giving the mag release another turn in by depressing the backside then turn the handle one complete turn.  He said "it sounds like the mags are dropping down after firing. The marks center round on the non-chambered bullet is an indicator of that. A metal mag, which is thinner than plastic would indeed be the first to drop. The plastic will tend to hold its position due to friction. They both need to hold their position due to the latch. Once you tighten up that mag release so more of it goes into the slot on the mag, now insert your mags with authority. Slap that mag home. Give it a tight pull to insure its snug. This is actually quite common on a new gun and one of the first things I'd check."

that will be my #1 adjustment now I think.  any opinions?

Yep, completely forgot about that.   That sounds super reasonable.   Check that out ASAP... quick and easy to do.    

I checked it (without firing b/c I'm not somewhere I can do that right now) but the mag seats very tight.  I tried my best to pull it down, but it wouldn't budge.  I did tighten the mag catch a lttle just in case.

Whatever you try, make sure you're throwing enough rounds downrange before you try something else... changing too many variables at once can make it confusing when you're troubleshooting an issue.

I'd say try different ammo first in all of the same magazines you had your Tula in. If you're still experiencing the issue, then check the magazines next.

One thing at a time. HTH.

Sounds like a gassing probuem either by the type of ammo your suing or mabey something came loose or dirty in you system...Id clean it well and use pipe cleaner on the gass tube and the pickup. also make the rings are clean... In other words clean the whole system//// : Last Id try a diffrent kind of ammo on the same mag and some on the mags you assumed were miss feeding.....

Somebody posted this at AR15armory.com:

http://www.youtube.com/watch?v=V5qDnKGJb2s

I'm gonna try brass ammo next and see.  I have a ton of the tula though, and if it won't shoot, I'm gonna change to a carbine upper since the guy at the gun shop said he would make it good if that's what I want to do.  I'm on a budget and at $5 a box for 20 rounds, it's tough to pass up.  I may like the carbine upper better anyway.

Also, measured my buffer spring and it is 11 and 15/16 inches. Shouldn't carbine length be shorter than that? The charging handle is really hard to pull when I chamber first round too.  Would a shorter spring give the BCG a better chance to cycle properly when using the lower pressure ammo like Tula?

Carbine action spring 10 1/16 min to 11 1/4 max.
Rifle action spring 11 3/4 min to 13 1/2 max.

So, it sounds like you have a rifle spring in your carbine.  A collapsible stock carbine needs to have a carbine buffer as well as a carbine spring.  Drop a new spring in there and let us know how it works.

Yes.  Bolt locks back with one round in the chamber.

Then its a Mag feed problem   Id try magpuls I havent had any problems with them I always keep 5 30 rounders loaded and never had a miss feed...

Went to the shop today and took my buffer spring out of my carbine stock.  Compared it to a spring out of another carbine stock.  Mine was a little over an inch longer.  Swapped them out.  Gonna see if that will do the trick.  Also, 2 magpuls will be here Friday.

My issue sounds like one of those "perfect storms" of problems:

Incorrect buffer spring
Lower pressure ammo
New mags not broken in yet

Fired 15 rounds from NHMTG mag and 11 from Thermold with no failures to feed after changing buffer spring!

Hope that does it!

Thanks for everyone's help.

Cool!  Thanks for the update.