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Equipment & Gear => Guns and Ammo => Topic started by: lokidog on March 28, 2020, 10:55:36 AM


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Title: Sticky AR bolt....
Post by: lokidog on March 28, 2020, 10:55:36 AM
Not saying that I own an AR, but, for a friend....

Any suggestions on what to check for with a sticky bolt? My "friend" has a newer, slightly used upper, 50-100 rounds through it, that won't close all of the way. The bolt was tried in an upper that functions fine and stuck about 1/4 inch short of closing every time it was cycled.

It was cleaned after shooting the last time.

TIA
Title: Re: Sticky AR bolt....
Post by: Dan-o on March 28, 2020, 11:15:26 AM
This also happened to a "friend" I know.   
Exact same symptoms.

When I.....    I mean when my friend finally throughly disassembled it, I found a small piece of brass jammed toward the front of the bolt.

I would thoroughly disassemble your friends AR.       
Title: Re: Sticky AR bolt....
Post by: jasnt on March 28, 2020, 12:04:09 PM
I’d pull the bolt and inspect lugs and pin groove that allows the lugs to lock. Also check the gas piston thingy can’t think of the proper term.  Make sure those screws are tight. Make sure the lugs turn smoothly as they cycle back
Title: Re: Sticky AR bolt....
Post by: fishngamereaper on March 28, 2020, 12:30:09 PM
Cleaned as in sprayed and wiped down or complete disassembly of BCG, bolt, etc... sounds like the bolt won't rotate and lock into the lugs.

Empty chamber or loaded?
Title: Re: Sticky AR bolt....
Post by: fishngamereaper on March 28, 2020, 12:36:52 PM
Also can you send it home with forward assist or does it stop...
Title: Re: Sticky AR bolt....
Post by: Alchase on March 28, 2020, 12:37:27 PM
This also happened to a "friend" I know.   
Exact same symptoms.

When I.....    I mean when my friend finally throughly disassembled it, I found a small piece of brass jammed toward the front of the bolt.

I would thoroughly disassemble your friends AR.       

That or a primer
Title: Re: Sticky AR bolt....
Post by: Jingles on March 28, 2020, 01:34:57 PM
Experienced a similar problem recommend disassembling the BCG and thoroughly cleaning  possibly something keeping it from completely seating.
Title: Re: Sticky AR bolt....
Post by: TooTallMike on March 28, 2020, 01:40:10 PM
Check your gas key and make sure it's not loose or marred up causing the carrier to hit the gas tube.

Then look at the cam pin. Had a similar issue once and it was a defect from the factory. Swapped it out and worked fine.

Finally check your lugs and disassemble as everyone else said.

Hope you get your "friends" gun up and running.
Title: Re: Sticky AR bolt....
Post by: jasnt on March 28, 2020, 04:12:03 PM
Check your gas key and make sure it's not loose or marred up causing the carrier to hit the gas tube.

Then look at the cam pin. Had a similar issue once and it was a defect from the factory. Swapped it out and worked fine.

Finally check your lugs and disassemble as everyone else said.

Hope you get your "friends" gun up and running.
and there are the terms I was fishing for ealier
Title: Re: Sticky AR bolt....
Post by: lokidog on March 28, 2020, 05:23:28 PM
It worked the last time I shot it. I did not disassemble the bolt for cleaning.

There are no marks or mars except maybe a little rub on the rear left corner of the bolt cam pin.

It will close using the forward assist.

When moving the bolt assembly into the carrier, there is some resistance as the bolt cam rotates back.

All screws seem tight.

I put this, I mean my friend put this bolt in another upper and it actually stuck shut.

I'd post photos but I moved locations and did not take his bolt with me. I might have access to it after Tuesday.  ;)

Thanks everyone for the input.
Title: Re: Sticky AR bolt....
Post by: JimmyHoffa on March 28, 2020, 06:02:26 PM
I'll also add cleaning the BCG.  I've had a few instances of the sticky bolt, especially when it is still cold.  Spraying WD40 didn't loosen it or trying to cycle by hand.  Had to clean all that carbon off in the bolt.
Title: Re: Sticky AR bolt....
Post by: fishngamereaper on March 28, 2020, 06:40:41 PM
Strip it down and clean it good. Problem solved.

Some powders will actually mix with some cleaners and a chemical reaction creates a solid..I've dug some nasty stuff out of BCGs.
Title: Re: Sticky AR bolt....
Post by: lokidog on March 28, 2020, 06:48:58 PM
Strip it down and clean it good. Problem solved.

Some powders will actually mix with some cleaners and a chemical reaction creates a solid..I've dug some nasty stuff out of BCGs.

Wish I had taken a photo, it is pretty darn clean.
Title: Re: Sticky AR bolt....
Post by: Dan-o on March 28, 2020, 06:56:11 PM
Strip it down and clean it good. Problem solved.

Some powders will actually mix with some cleaners and a chemical reaction creates a solid..I've dug some nasty stuff out of BCGs.

Wish I had taken a photo, it is pretty darn clean.

Good to know your friend cleaned it well.

I'd still take the BCG down to parts and clean it.

That has also been a cause for my friends' AR sticking in the past.
Title: Re: Sticky AR bolt....
Post by: lokidog on March 28, 2020, 07:17:56 PM
He might try buffing the bolt cam a bit.
Title: Re: Sticky AR bolt....
Post by: TooTallMike on March 28, 2020, 08:18:41 PM
Also consider stripping it and seeing if the carrier itself will slide freely into the upper. Then try it with the charging handle and if they do then it narrows it down to the cam pin and bolt.

Just two days ago I fixed a jacked looking carrier that had LOTS of resistance going through the upper. Turns out it was the staking on the gas key that was causing the while issue. Dremel and 8 seconds on each side and that bad boy was butter.

Title: Re: Sticky AR bolt....
Post by: TooTallMike on March 28, 2020, 08:19:50 PM
Check your gas key and make sure it's not loose or marred up causing the carrier to hit the gas tube.

Then look at the cam pin. Had a similar issue once and it was a defect from the factory. Swapped it out and worked fine.

Finally check your lugs and disassemble as everyone else said.

Hope you get your "friends" gun up and running.
and there are the terms I was fishing for ealier

I'll gladly offer the correct terms when I can. I just appreciate your builds and the INSANE performance of them.

Keep it up 👍
Title: Re: Sticky AR bolt....
Post by: jasnt on March 28, 2020, 09:48:56 PM
Check your gas key and make sure it's not loose or marred up causing the carrier to hit the gas tube.

Then look at the cam pin. Had a similar issue once and it was a defect from the factory. Swapped it out and worked fine.

Finally check your lugs and disassemble as everyone else said.

Hope you get your "friends" gun up and running.
and there are the terms I was fishing for ealier

I'll gladly offer the correct terms when I can. I just appreciate your builds and the INSANE performance of them.

Keep it up 👍
thank you. Will do
Title: Re: Sticky AR bolt....
Post by: lokidog on March 28, 2020, 09:57:49 PM
Also consider stripping it and seeing if the carrier itself will slide freely into the upper. Then try it with the charging handle and if they do then it narrows it down to the cam pin and bolt.

Just two days ago I fixed a jacked looking carrier that had LOTS of resistance going through the upper. Turns out it was the staking on the gas key that was causing the while issue. Dremel and 8 seconds on each side and that bad boy was butter.

The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.
Title: Re: Sticky AR bolt....
Post by: NitRally on March 28, 2020, 10:34:08 PM
Check the gas rings. The three tiny washers on the end of the bolt make sure all the spaces are equally separated.
Title: Re: Sticky AR bolt....
Post by: NitRally on March 28, 2020, 10:38:32 PM
Had a similar problem, the rings were getting bound in the carrier. Hope this helps. (If they're mangaled they're like 5 bucks for all 3.)
Title: Re: Sticky AR bolt....
Post by: JimmyHoffa on March 28, 2020, 10:40:44 PM
Ammo?
One time, back when I was slightly more of a moron, I didn't fully resize a batch of cases.  The die was just a hair to high, but length was good.  The shoulder was a bit of an issue and was giving problems when trying to send the bolt home.
Title: Re: Sticky AR bolt....
Post by: lokidog on March 29, 2020, 11:32:21 AM
Ammo?
One time, back when I was slightly more of a moron, I didn't fully resize a batch of cases.  The die was just a hair to high, but length was good.  The shoulder was a bit of an issue and was giving problems when trying to send the bolt home.

Factory

Also consider stripping it and seeing if the carrier itself will slide freely into the upper. Then try it with the charging handle and if they do then it narrows it down to the cam pin and bolt.

Just two days ago I fixed a jacked looking carrier that had LOTS of resistance going through the upper. Turns out it was the staking on the gas key that was causing the while issue. Dremel and 8 seconds on each side and that bad boy was butter.



I'm thinking cam pin at this point and will take a look at my friend's bolt assembly in a day or two. The cam pin does seem to slide and rotate more easily on the "working" one.
Title: Re: Sticky AR bolt....
Post by: Yondering on March 30, 2020, 10:54:48 PM

The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.

That would have been a good detail to include in the first post. Way too much of this thread is just guessing without enough info, as is typical of internet problem diagnostics.

If the problem only happens when a cartridge is in the chamber, then it has nothing to do with the gas rings, cam pin, gas key, etc or any of that stuff. You've either got an extractor problem, or something causing the ammo to not fit the chamber (this is the most likely).

Did you switch ammo? Are these reloads? Is the chamber dirty?
Figuring out why your ammo doesn't fit the chamber is the first step. I wouldn't bother with any of the other things suggested here until you do that.

If it's not anything obvious, you can color a cartridge with a sharpie marker (color the entire case and the bullet), then try to chamber it, and look where the sharpie rubbed off. Some scratches on the case neck and bullet are normal from extracting a live round; you're looking for some sort of rub mark or maybe a ring that goes all the way around the case or bullet.

Hope that gets you started in the right direction.
Title: Re: Sticky AR bolt....
Post by: dreadi on March 30, 2020, 11:38:35 PM
Has it been determined that the bolt is the correct bolt for the caliber of the gun?
Title: Re: Sticky AR bolt....
Post by: lokidog on March 31, 2020, 11:20:17 PM
Has it been determined that the bolt is the correct bolt for the caliber of the gun?

Yes


The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.

That would have been a good detail to include in the first post. Way too much of this thread is just guessing without enough info, as is typical of internet problem diagnostics.

If the problem only happens when a cartridge is in the chamber, then it has nothing to do with the gas rings, cam pin, gas key, etc or any of that stuff. You've either got an extractor problem, or something causing the ammo to not fit the chamber (this is the most likely).

Did you switch ammo? Are these reloads? Is the chamber dirty?
Figuring out why your ammo doesn't fit the chamber is the first step. I wouldn't bother with any of the other things suggested here until you do that.

If it's not anything obvious, you can color a cartridge with a sharpie marker (color the entire case and the bullet), then try to chamber it, and look where the sharpie rubbed off. Some scratches on the case neck and bullet are normal from extracting a live round; you're looking for some sort of rub mark or maybe a ring that goes all the way around the case or bullet.

Hope that gets you started in the right direction.

Don't know what to tell without someone asking. ;-)

There is some odd wear on the cam pin corner that turns into the receiver, see pic.

HOWEVER, with a little more research on my "friend's" gun, it turns out to only happen with the HexMags and not the PMags in both receivers. I dug out the micrometer and there are slight differences in dimensions on various parts of the bolt body.

The "sticky" bolt works with the PMags in both receivers. I found someone that sanded the top edge down a little so decided to try that, seems to be getting better as I shave the top down slightly.

Thanks everyone for the suggestions.
Title: Re: Sticky AR bolt....
Post by: lokidog on April 01, 2020, 12:11:17 AM
So, I reshaped the front of one of the magazines to look more like the PMag. It was a little better, but not a lot. I then noticed that the magazine popped in easily with the bolt open but not so easily with it closed so I shaved the highest point down just slightly and... voila. It cycles nicely now.

I'm still curious about the wear in the previous photo though.
Title: Re: Sticky AR bolt....
Post by: TooTallMike on April 01, 2020, 12:47:37 AM
What upper is it running?

Have you inspected the inside of the upper?
Title: Re: Sticky AR bolt....
Post by: lokidog on April 01, 2020, 07:40:50 AM
What upper is it running?

Have you inspected the inside of the upper?

It behaves the same in both uppers that my friend has....

One upper was a build project, don't remember the bolt or upper maufacturer. That one works with both unmodified magazines. The other is an upper from 22modsforall. That is the one with the issues with the HexMag, and the bolt has those issues in both of the uppers.

There are other people on the internet that have had this issue with the HexMag (gen 2).
Title: Re: Sticky AR bolt....
Post by: Yondering on April 01, 2020, 02:45:24 PM
Has it been determined that the bolt is the correct bolt for the caliber of the gun?

Yes


The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.

That would have been a good detail to include in the first post. Way too much of this thread is just guessing without enough info, as is typical of internet problem diagnostics.

If the problem only happens when a cartridge is in the chamber, then it has nothing to do with the gas rings, cam pin, gas key, etc or any of that stuff. You've either got an extractor problem, or something causing the ammo to not fit the chamber (this is the most likely).

Did you switch ammo? Are these reloads? Is the chamber dirty?
Figuring out why your ammo doesn't fit the chamber is the first step. I wouldn't bother with any of the other things suggested here until you do that.

If it's not anything obvious, you can color a cartridge with a sharpie marker (color the entire case and the bullet), then try to chamber it, and look where the sharpie rubbed off. Some scratches on the case neck and bullet are normal from extracting a live round; you're looking for some sort of rub mark or maybe a ring that goes all the way around the case or bullet.

Hope that gets you started in the right direction.

Don't know what to tell without someone asking. ;-)

There is some odd wear on the cam pin corner that turns into the receiver, see pic.

HOWEVER, with a little more research on my "friend's" gun, it turns out to only happen with the HexMags and not the PMags in both receivers. I dug out the micrometer and there are slight differences in dimensions on various parts of the bolt body.

The "sticky" bolt works with the PMags in both receivers. I found someone that sanded the top edge down a little so decided to try that, seems to be getting better as I shave the top down slightly.

Thanks everyone for the suggestions.

OK, so that's different again from what you said. It sounds like the issue is when a magazine is in the gun, not necessarily when a cartridge is in the chamber. That points to a magazine issue, as you said. It's hard to give accurate suggestions without the correct info. On the flip side of that, beware of people who do give suggestions without having much info; they're probably guessing just as much as you are.

Glad you got it figured out.
Title: Re: Sticky AR bolt....
Post by: lokidog on April 01, 2020, 08:21:47 PM
OK, yeah I guess I didn't say with a magazine and cartridges...   :sry:
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 01:06:04 PM
Having this same problem with my brand new bushmaster upper.  Wouldnt close all the way, i pull back charging handle and cartridge stays in chamber.  I drop charging handle again and push it in, VERY hard to pull back, when it does, the cartridge comes out stuck in the bolt face, scuffed up brass when i pop it off.  Switched ammo types and tried again, only this time i cant pull the charging handle out, its flat stuck.
Title: Re: Sticky AR bolt....
Post by: hunter399 on April 03, 2020, 01:16:19 PM
Having this same problem with my brand new bushmaster upper.  Wouldnt close all the way, i pull back charging handle and cartridge stays in chamber.  I drop charging handle again and push it in, VERY hard to pull back, when it does, the cartridge comes out stuck in the bolt face, scuffed up brass when i pop it off.  Switched ammo types and tried again, only this time i cant pull the charging handle out, its flat stuck.
Slam the butt of the rifle down on something while trying to pull the charging handle,it will come out.

A lot of places are cutting chambers so quick these days. :dunno:

Did you ever cancel that bear crk rifle or does your bear crk rifle work better than your new bushmaster upper :chuckle:
Title: Re: Sticky AR bolt....
Post by: lokidog on April 03, 2020, 01:27:43 PM
Bango, did you drop your magazine? this helped when mine stuck a couple of times while trying to figure it out.
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 01:28:11 PM
Having this same problem with my brand new bushmaster upper.  Wouldnt close all the way, i pull back charging handle and cartridge stays in chamber.  I drop charging handle again and push it in, VERY hard to pull back, when it does, the cartridge comes out stuck in the bolt face, scuffed up brass when i pop it off.  Switched ammo types and tried again, only this time i cant pull the charging handle out, its flat stuck.
Slam the butt of the rifle down on something while trying to pull the charging handle,it will come out.

A lot of places are cutting chambers so quick these days. :dunno:

Did you ever cancel that bear crk rifle or does your bear crk rifle work better than your new bushmaster upper :chuckle:

Well, that was easy hitting the butt on a stump to pop the charging handle out, and this time the cartridge didnt stick to the bolt doing it this way.  Heres a pic showing the chewed up brass on the rim of the cartridge.

The bca rifle works fine.  I just built a new lower, and im about to do my. 223 wylde upper for it, but first i popped this complete 450 upper on to try it out.  Not going so well.  But wanting to make sure i didnt screw up my lower build, never having done it before, i took my upper off my bca rifle and put it on my new lower, and it worked properly.
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 01:28:30 PM
Bango, did you drop your magazine? this helped when mine stuck a couple of times while trying to figure it out.

Yeah
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 01:34:37 PM
Didnt expect to have problems here, its not a cheap upper.  Next level armament.  Has a tromix barrel.
Title: Re: Sticky AR bolt....
Post by: hunter399 on April 03, 2020, 01:40:51 PM
@Bango
I'm gonna urge ya to just go with a ar10 ,with some of that 💰. Ar15 is very addicting,but once you bump up to ar10 YOU wont  play with them anymore.Been seeing 243,6.5,308 are popular these days.
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 02:18:35 PM
Im not looking to buy an ar10.  This upper should work.  It was 800 dollars and took a month to get it.  Pretty bummed.  Cant find anything stuck in the chamber, dont know what the deal is.
Title: Re: Sticky AR bolt....
Post by: JimmyHoffa on April 03, 2020, 02:38:51 PM
Thinking the chamber wasn't cut right?
Are you able to unscrew the barrel?
Title: Re: Sticky AR bolt....
Post by: Yondering on April 03, 2020, 03:05:39 PM
@Bango
I'm gonna urge ya to just go with a ar10 ,with some of that 💰. Ar15 is very addicting,but once you bump up to ar10 YOU wont  play with them anymore.Been seeing 243,6.5,308 are popular these days.

Do you even own one?

You've been giving a lot of suggestions about ARs on this forum that are questionable, at best.
Title: Re: Sticky AR bolt....
Post by: hunter399 on April 03, 2020, 03:16:50 PM
Im not looking to buy an ar10.  This upper should work.  It was 800 dollars and took a month to get it.  Pretty bummed.  Cant find anything stuck in the chamber, dont know what the deal is.
:yike: :yike: :yike:
Wow -Holly smokes
I put my my whole ar10 together for less than that.There probably is ways of fixing it .but for that money I would get my money back.
Title: Re: Sticky AR bolt....
Post by: hunter399 on April 03, 2020, 03:18:51 PM
@Bango
I'm gonna urge ya to just go with a ar10 ,with some of that 💰. Ar15 is very addicting,but once you bump up to ar10 YOU wont  play with them anymore.Been seeing 243,6.5,308 are popular these days.

Do you even own one?

You've been giving a lot of suggestions about ARs on this forum that are questionable, at best.
Didn't see you giving him advise on how to get his stuck round out of the chamber .You got a better method maybe chime in next time.
Title: Re: Sticky AR bolt....
Post by: hunter399 on April 03, 2020, 03:24:09 PM
Im not looking to buy an ar10.  This upper should work.  It was 800 dollars and took a month to get it.  Pretty bummed.  Cant find anything stuck in the chamber, dont know what the deal is.
Yondering seems like he knows what he is talking about he can give ya advise.
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 03:32:55 PM
Thinking the chamber wasn't cut right?
Are you able to unscrew the barrel?

The brass is getting scuffed all the wsy down, so maybe, but the barrel came dirty so it had to be test fired  :dunno:

Having never put together an upper, im not going to take this one apart.  Yet.  I just finished my first lower, and now im about to put together a 223 wylde upper.  Once i do that, and see how all the bits and pieces go together, then ill consider breaking the 450 upper down.  But i dont have headspace gauges for the 450, so i dont kniw what i could accomplish as far as determining whether or not the chamber is out of spec.
  From what i can see, when putting a cartridge in the chamber with the bcg removed, the cartridge sits flush right here, where the taper starts.  Dont know if this is normal, or if its supposed to sit deeper.  This is all new territory for me. 
Title: Re: Sticky AR bolt....
Post by: JimmyHoffa on April 03, 2020, 03:48:09 PM
That would look fine to me.
Title: Re: Sticky AR bolt....
Post by: hunter399 on April 03, 2020, 03:53:45 PM
For the money you paid,I would expect any upper to function flawless and not have to tear it apart. :twocents:
That's my only advise.
I could tell look here ,do this,but should not have too .
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 04:08:58 PM
For the money you paid,I would expect any upper to function flawless and not have to tear it apart. :twocents:
That's my only advise.
I could tell look here ,do this,but should not have too .

My feeling exactly.  Should be plug n play, bang away.  Im not happy.
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 05:04:45 PM
With the bcg taken out, i can drop a cartridge into the chamber and drop it out no problem, no friction. Wouldnt that indicate that the problem is with the bolt, not the chamber?

The bolt has no markings on it to indicate which caliber it is intended for, and one thing of note is that NLA's explanation for why it was taking so damn long to ship was that they were waiting on BCGs
Title: Re: Sticky AR bolt....
Post by: JimmyHoffa on April 03, 2020, 05:11:05 PM
In one of your pictures, the extractor marks don't look like they went far enough over the rim.  Is the ejector jammed forward? 
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 05:13:14 PM
No, i can push the ejector in and out
Title: Re: Sticky AR bolt....
Post by: JimmyHoffa on April 03, 2020, 05:17:11 PM
Dang.  You drug me down your rabbit hole.
I did come across this.  Maybe interesting?
http://bulletin.accurateshooter.com/2014/08/ar-ejector-mod-for-improved-reliability-with-larger-cartridges/
Title: Re: Sticky AR bolt....
Post by: Bango skank on April 03, 2020, 05:20:53 PM
Dang.  You drug me down your rabbit hole.
I did come across this.  Maybe interesting?
http://bulletin.accurateshooter.com/2014/08/ar-ejector-mod-for-improved-reliability-with-larger-cartridges/

Interesting, my ejector is square face, but was clearly beveled, which i was wondering if that was damage.  Seems pretty hoaky for an 800 dollar upper to have a ghetto rigged ejector instead of just the proper rounded one.  Im thinking this is just going to get returned.
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