Yesterday I took out an AR to try to sort out questions I’m having with a thermal sight, and ran into troubles with the rifle itself. Several times, I got the dreaded “Click! Fudge!” effect. Or worse, not even a click.

Several times, trying to clear the error, I dropped the magazine and attempted to open the chamber. I had to do some serious yanking on the charging handle to get it to open up. Haven’t experienced that before.

Later, I noticed the bolt wasn’t closing all the way.



So today I removed and disassembled the bolt, cleaning away some carbon and gunk, and put it all back together, including oiling it all.

And what I find now is that if I let the bolt close gently, it does still stick just short of closing all the way. I can tap the rear of the charging handle gently, or smack the forward assist, and the bolt clanks home like it ought to.

I can’t get to the range again today, but I’m left wondering if I’ve got something going on other than jst that it needed a clean-and-lube.



Am I being too gentle today, and just need to let things slam home? Or did yesterday’s symptoms indicate a bigger problem?
I’ve got about a month in which to get this rifle ready for a hog hunt, and I’m kind of excited about that. This unreliability, though, is pretty darned discouraging.

Thanks, all.

Let that bitch rip, unless you're working behind enemy lines and charging the gun surreptitiously.

A few of my guns will do this. I'm also not keen on cleaning or lubing until I see an issue, so maybe that's my problem.

There’s normally a small amount of drag from the gas rings on the bolt rubbing on the inside of the bolt carrier. Did you recently change the rings? Even if you didn’t, it’s normal for a little bit of force to be needed for the bolt to be pushed back inside the carrier. Have you even cleaned the inside of the carrier where the bolt travels?

Let it rip… got it. Thank you, Mike.

Dwill: I haven’t changed rings or anything — this upper has only about 50-60 rounds through it. While I had it apart today, I did make sure the rings did not align with one another, I know that’s a bad thing. I did clean the inside of the carrier today.

As for the drag you mention: I did notice on reassembly that the bolt has some drag — it’s not as if I could hold the bolt and shake the assembly, and watch the carrier slide along it smoothly. Thank you for pointing out that the drag is normal.

quote:

Originally posted by vthoky:
I did make sure the rings did not align with one another, I know that’s a bad thing.

No, not really as gets discussed here from time to time.

Anyway, if my rifles are reasonably clean, I can’t get the bolt to stay open that little bit even when I let it go forward as slowly as possible (for demonstrations of the forward assist). If cleaning helped perhaps there is still some more stuff in/around the barrel extension that could be cleaned out.

But to clarify, does the bolt stay partially out of battery like in the pictures when a round is fired, or just when closing it by riding the charging handle forward? If when a round is fired, the action isn’t going to be any faster and stronger when doing it by hand, and there is an issue that needs correcting.

If you’ve thoroughly cleaned not only the bolt but the barrel extension as well, it might be worth seeing if there is any hesitation when the bolt is placed in the extension and rotated into its normal locked position. Perhaps there is a burr of some sort inside the extension. Check the fit and movement by manipulating just the bolt by hand.

And check your buffer spring. Make sure everything is operating smoothly.

Is this with a round in the chamber? Does it fail to go ‘home’ without a round loaded?

If loaded, what ammo? Reloads?

quote:

Originally posted by sigfreund:
But to clarify, does the bolt stay partially out of battery like in the pictures when a round is fired, or just when closing it by riding the charging handle forward? If when a round is fired, the action isn’t going to be any faster and stronger when doing it by hand, and there is an issue that needs correcting.

Yesterday, I was seeing the bolt stay partially out of battery after firing a round. I’d put two or three rounds in the magazine, fire one, and get held up on the next one. In order to clear things, I’d have to drop the magazine, yank the heck out of the charging handle, reinsert the magazine, and let the bolt slam forward again.

quote:

Originally posted by sigfreund:
If you’ve thoroughly cleaned not only the bolt but the barrel extension as well, it might be worth seeing if there is any hesitation when the bolt is placed in the extension and rotated into its normal locked position. Perhaps there is a burr of some sort inside the extension. Check the fit and movement by manipulating just the bolt by hand.

I have not cleaned the barrel extension today, but can surely do that next.

quote:

Originally posted by YooperSigs:
And check your buffer spring. Make sure everything is operating smoothly.

What should I be looking for regarding the spring? It compresses and extends… beyond that, I’m not sure what to check

quote:

Originally posted by sourdough44:
Is this with a round in the chamber? Does it fail to go ‘home’ without a round loaded?

If loaded, what ammo? Reloads?

Pics (above) were taken today, with no ammo around, though I saw the same effect yesterday after around was fired.

I neglected to mention in my original post that we were shooting with a suppressor.

Ammo was all new — The first 20 rounds yesterday were Hornady Black 208-gr subsonic (80891), followed by five Hornady 80897 125-gr. Difficulties were common across the two types.

Also, a couple of the 80891 didn’t feed properly — I recovered at least one whose red polymer tip had become deformed.

To reiterate, if the bolt is left out of battery as pictured when firing ammunition, then there is definitely an issue that needs to be corrected. As I say, it’s difficult to even set the bolt carrier in that unlocked position when I’m trying to demonstrate the use of the forward assist. When the BCG is pushed forward by the action spring its inertia should easily be enough to close it into the locked position even if the action spring is a little weak for some reason.

When I clean an AR and insert the BCG along with the charging handle, light finger pressure is enough to lock the bolt into the barrel extension.

To clarify what I was referring to about testing the fit of the bolt in the barrel extension, do that with the bolt by itself, not in the BCG. You should be able to feel any resistance when doing that by hand. It may be a little tricky to get the bolt lined up correctly, but then it should go into the extension and rotate relatively freely.

As you probably know, if the gun is somehow managed to be fired without the bolt being properly rotated and locked into the barrel extension, that is a very dangerous situation for not only the gun but the shooter as well.

What caliber is the gun? What caliber is the ammo? lol

Once upon a time that was difficult to do. Now days not so much.
I was rather frustrated this winter when my 6ARC ammo wouldn't chamber in my .22ARC.

quote:

Originally posted by sigfreund:
To clarify what I was referring to about testing the fit of the bolt in the barrel extension, do that with the bolt by itself, not in the BCG. You should be able to feel any resistance when doing that by hand.

Thank you. I can try that later this evening.

quote:

Originally posted by cas:
What caliber is the gun? What caliber is the ammo? lol

Both are .300 Blackout.

I would also check to be sure the gas tube is not rubbing on the gas key if this a direct impingement upper.

McGregor: your post led me to a search that led me to this video.



Is that the effect you had in mind? The “stall” shown in the video looks a lot like what I saw this afternoon.

I did replace the gas block last week, installing a Superlative Arms adjustable block. Could I have jacked up the gas tube position in the process?

I also found this video:



Based on that, it appears I did the gas block installation correctly. I didn’t have the nice gadget he’s got for holding the block while installing the roll pin, but with a vise and a small punch I got it done….

quote:

Originally posted by McGregor:
I would also check to be sure the gas tube is not rubbing on the gas key if this a direct impingement upper.

Thank you. That is not something I had ever heard of to consider.

After more surfing…

Did I do the wrong thing by putting the gas tube into the gas block before installing the block onto the barrel?



- - - - -

ETA:

Perhaps I didn’t mess up: RTFM, vthoky!

Though I did miss that part about the .025 gap between the shoulder on the barrel and the back of the gas block.

I’ll take it apart tomorrow evening and get that gap.

vthoky, yes the gas tube bind is what I was thinking of.

Now I'll have to check a recent build of mine in reference to the .025" gap between the gas block and the barrel shoulder though I did use a borescope to line up the the barrel and gas block holes.

I don't think you did it wrong by putting the gas tube in the block before installing the block on the barrel. This is what I did so as not to potentially upset the block location on the barrel.

I would also be curious about the barrel extension being slightly clocked. It's not terribly uncommon. I would inspect the bolt lugs for peening or other damage and do some really deliberate slow hand cycling with a clean gun to see if there's a chance the lugs are colliding with part of the barrel extension. This is the kind of issue that might not appear until the gun is dirty or dry.

The .025" gap from the barrel shoulder is only needed if your gas block was designed to go against a handguard end cap. With the current market of free float, low-profile gas blocks it's a tossup as to whether yours is or not, and there are a lot of brands who wouldn't be able to tell you if you asked. I would start with asking if you're not sure.

If you do pull the gas block there should be a pretty obvious witness mark as to any overlap or misalignment. If your gun is ejecting fine and locks back at the end of magazines I wouldn't think you have a gassing issue from something like a misaligned gas block.

The video of the gas tube misalignment is mostly correct, but I wouldn't perform the diagnosis with the bolt present, and would go a step further and perform the following test instead of the subjective feel shown;
1. Remove the bolt, cam pin, firing pin from the carrier, and charging handle from the upper
2. Place the upper receiver on a flat surface pointed down, resting on the barrel
3. Slide the carrier into the upper until it's 1/2" from contacting the gas tube
4. Drop the carrier onto the gas tube

If the carrier drops and seats fully, and contacts the barrel extension you don't have any alignment issues, regardless of how the engagement feels. If it hangs up on the gas tube or seemingly hits a ledge you do have alignment issues. This is assuming there is no evidence of wear on the two parts and they're in spec.

If your bolt is contacting the barrel extension there should be evidence. The bolt will peen over, or at the very least have some finish wear. The same for the barrel extension. Even if it's shiny, hard surfaces like chrome and NP3 there will be some marking from a misaligned bolt.

The bolt's gas rings can hang up on a messy bore of the BCG. The fit of the cam pin to the bolt/carrier could be loose. You could have a blown primer hanging out in your barrel extension (had that happen before and presented the same way).

There could be further issues, a combination of several, not very easy to diagnose over the internet.

Thanks for all that, Rustpot; good information.