First AR build...cycling issues. UPDATE 8/4/17 PROBLEM SOLVED

Switch

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As mentioned I just finished my first AR 15 (.223) build and shot it for the first time today. I had an issue that I'm hoping the members here can help me with.

Here are the sequence of events:

Charge handle and BC pulled back to verify unloaded. I did not use the bolt catch to keep the bolt back.

Inserted 10-round mag, made sure it was seated and pulled charge handle/bolt assy back and released. Watched the round advance and noticed the bolt seated all the way forward.

Aimed down range, Squeezed trigger once and rifle fired successfully. Brass ejected successfully.

Before a second pull I noticed that the bolt did not seat fully forward. It looked to be back by 1/4 inch.

Using the forward advance knob it would not move forward. I dropped the magazine and noticed a round was not picked up by the bolt...empty chamber.

I tried two different mags...same result.

This happened 8-10 times. Mag inserted, fires once and no round picked up. I took down the rifle and didn't notice any issues. Reassembled and tried again. Same result.

It appears that the bolt is advancing back far enough to eject the brass, but not far enough to pick up a second round out of the mag.

Complete upper: CBC 20" .223/5.56 1:9 straight flute
Bolt Carrier Assemble Complete: Black Rifle Works, 5.56mm/.223 (BNC)

Ammo: varied 5.56/.223 head stamps. I accidently grabbed the wrong bag of ammo before I headed out, leaving the V-max .223 Rem at home.

Any assistance would be helpful...thanks.
 
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Originally Posted By: SwitchBefore a second pull I noticed that the bolt did not seat fully forward. It looked to be back by 1/4 inch.

Using the forward advance knob it would not move forward.


everything else aside, this ^^^^^ is what has me baffled.
did it do this every time?
 
My first build did this. I thought I had the gas block aligned right but did not. I swapped out the gas block(cheap block) made sure it was aligned properly and the problem went away. I'm with the rest of theses guys. Under gassed or/and block not aligned properly.
 
Slicker than Snot, no it didn't do this every time. I remember it doing this twice.

I will check the one round in the mag, bolt lock back deal the next time I'm out.

Having read some additional information, it seems like it could be quite a few thing causing the issues.

Magazine problems: I am running two magazines, both Magpols. The issue occurred with both mags making me lean towards it NOT being the mag issue.

Lubrication problems: I lubed up the bolt pretty good prior to the test firing. I have since wiped it down per a suggestion and only oiled up the bolt carrier rails and the bolt area behind the ejector.

Running a Rock River arms trigger: the hammer can apparently contact the bottom of the bolt during re-charge, robbing it of motion. I'm looking into getting space measurements for this.

Buffer spring issues: My spring is 10.5 inches long and has 36 coils. I guess rifle springs are supposed to be 11 3/4 to 13 1/2 with 41-43 coils. I also do not know the weight of the actually buffer. I'm wondering if this tighter spring is precluding rear motion enough to limit recharge. I understand that the one round in the mag deal may tell me more here...anxious to get out and try that.


Gas issues: as was mentioned here. The alignment looks good and the tube mates up with the port on the bolt perfectly.

Other things I'm going to try:
I have a buddy that has just finished his AR. I might switch out lowers to see if the RRA trigger is an issue (he's running a different trigger).

I'll run out today and try the one round in the mag/ bolt lock back deal today. I think that'll tell me a few things.

I seriously appreciate the help guys and will continue to work on it and hopefully figure this out. I sure am learning a lot about the entire rifle and how it functions. Thanks again and I'll keep everyone updated if they'd like!
 
Please do, The only way to learn is from trial and error. There are so many different things to make them run right. I guess that's why I still like my bolt guns best, even though, the fast follow up shot/shots sure are nice. Good Luck on your diagnosis.
 
OK, new information.

I hit the range today and I loaded a single factory .223 Rem round into the magpol magazine (I decided to eliminate the ammo variable by only pushing .223 through my AR), loaded the AR, charged it, shouldered it tight and pulled the trigger. The round fired and the bolt stayed back ****** (I explain the *** a little later.

I repeated the above step and once again the bolt stayed back. I figured maybe the problem was solved and removed the magazine and loaded three rounds. Charged it, shouldered it and fired. The round fired, but the bolt did not pick up the second round. I dropped the mag, loaded a single round and repeated step one. The bolt stayed back...or so I thought.

**** Upon visual inspection the bolt is back and the chamber open. However, when I dropped the magazine, the bolt slammed forward, so it wasn't locked back like it should've been if you had come to the last round in the magazine. I couldn't remember if this happened with the first two shots.

I repeated the single round exercise two more times and the bolt DID NOT stay back like it had the two first two times.

In all cases where the mag was loaded with multiple rounds, the bolt did not pick up the second round, but was fully closed. In each of these cases I removed the upper and noticed that the bolt did traveled back to lock back the trigger.

TRIGGER: I have read a few places that the Rock River Arms trigger (the one I have installed) can contact the bottom of the bolt and impede the movement, robbing it of it's momentum. If this is the case, I believe it would result in the issues I'm having.

BUFFER SPRING: I also read where the wrong buffer spring may cause issue. I removed mine and noticed it was only 10 1/2 inches long with 35 coils, more suited for an AR pistol. The rifle buffer spring calls for 11 3/4 -13 1/2 inches with 41-43 coils. If the stouter buffer spring is stopping the buffer and bolt sooner than it should, I believe it would also result in the issues I'm having.

UNDER GASSED: Obviously this is the more complicated of the three. I purchased a completed upper from CBC, so the gas tube and block were already assembled. Before I call them and ask for assistance, I want to eliminate all variables and work on the two issues above.

As always, any suggestions the members may have are appreciated. I'll keep everyone updated as I move forward.
 
Seems pretty clear that you are just short enough gas/momentum to get full rearward travel. I'd try a more appropriate spring and see if that solves it. You never shared which gas system length it has that I've seen....
 
If you have a buddy that has a different trigger group in his lower use it and see if that eliminates it. Also,if he will let you,pull his spring if it is rifle length and put it in yours and see what happens
 
Springer, I just measured the factory CBC complete upper gas system length and from the front of the gas block to the end of the port tube is about 15.5 inches.

So, Yotekiller and Springer have both picked up on the buffer spring issue. After further investigating, it looks like I definitely have a carbine length buffer spring in the rifle. The coil number for that spring is 37 coils. It looks like I need a rifle length buffer spring with 43 coils.

Trigger issue: I have searched for a few days and have not seen any mention of the RRA trigger having issues in an AR build except once through an old post here, so I'm thinking that is not a problem.

I'm now ordering a new rifle-length buffer spring and report back when I take it back to the range.

Thanks again!
 
The trigger hammer is suppose to ride on the underside of the bolt Carrier Group. Is the hammer trigger you have, one of the ones that has the big hook on the back or one of the ones without. Sometimes the big hook on the back bottoms out inside receiver. If it's a RR I doubt its the trigger group.
 
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MG, thanks for the advice. The trigger hammer is rounded, no hook. I read someplace where the RRI trigger may be an issue, but after a thorough on line search, I'm with you, I don't think that's the problem.

A new Tubbs, flat wire buffer spring is on the way. If that doesn't solve the issue, I'm moving on to the gas block and gas system.
 
Oil the crap out of the BCG... Also lube the buffer tube... Might help being its a new build also..
 
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Thanks to everyone who has sent me PM's suggesting fixes for the my first AR 15 build. Here are the specifics of the issue after the last two range trips.

Rifle specifics:
.223 Wylde 20-inch upper and Black Rifle Works BC
Shooting only factory .223 ammo
Brass looks clean
Ejection: 3:00-4:00 consistently.
Have used three different magazines, all Magpol.

Rifle will not cycle more than one round and the bolt fails to stay open using the one round test.
Replaced buffer spring with a Tubbs flat wire tube. This DID NOT solve the problem.

In the spirit of trying to figure out the problem, I have decided to make a single fix/adjustment between each range trip to see if I can pinpoint the problem. Note: I do understand that trading out parts (BC, upper and lower) with another AR will eliminate certain parts, but I do not have another AR and my buddies build will not be completed until later this week.

Most recent trip: With the new Tubbs buffer tube, I headed out with three different magazines and two different types of factory .223 ammo. As I suspected, the new spring did not solve the problem.

I conducted single round mag checks and all three mags did the same thing. After charging and picking up the only round in the mag, the rifle fired perfectly and ejected the brass in the 3:00-4:00 range consistently. However, the bolt did not remain open like it should. It does travel back enough to reset the trigger, but not far enough back to engage the bolt catch.

I loaded one shell in all three mags and did the above exercise a total of four times (a total of 12 rounds)and in all cases the bolt did not remain open and the trigger was reset.

I took the rifle apart and noticed that the underside of the BC had some wear on it, as did the hammer of the trigger. To me, this wear seems a bit excessive for a rifle that has been charged and checked 20 times during the build and firing 30 rounds through it. See attached photos.

I am running a RRA trigger and there has been some discussion that the large hammer may rob the momentum of the BC when traveling back, essentially keeping it from fully traveling back to either grab another round or engage the bolt catch.

I would like to say that Dave, from Black Rifle Works has been beyond helpful and assures me that we'll figure it out, even calling to discuss the issue.

My next action will be to trade out parts with my buddies AR and pinpoint the issue. Before I start taking down metal of the RRA hammer, I want to see if my buddies lower (different trigger) will ride smoothly. Again, thanks for all the advice and I hope that the steps I'm taking will help someone else down the line.

The new flat wire spring at the top and the one I replaced on the bottom.


Noticeable wear on the underside of the BC.


Noticeable wear on the hammer of the trigger.


My buddy is running a different trigger and as soon as we can trade out parts, I should be able to eliminate some problems and hopefully pinpoint the issue.
 
do you have a way to measure the diameter of the gas port on the barrel? check the port for restrictions/burs? or possibly thread on a krinkov device to add back pressure to test function.

I had a barrel that had all the same symptoms and the problem ended up being an undersized gas port.
 




That is a carbine buffer in your picture. From your previous posts, you are running a rifle buffer tube and spring so you need a rifle buffer. Change that out and you will probably be in business
 
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Also try some different magazines. I had some Magpuls that would not lock the bolt back. Use your buddies magazine if it's metal. If not order a metal magazine and see how it operates.
 
Is the bolt catch latch free. I had one that had a small burr on it. Filed it off and it worked just fine. Of course that will not fix the failure to feed, or will it???????????
 
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