AR10 bolt Rub

The description of your buffer throws up a caution flag for me, so just to verify, what is the actual length of your buffer?

When you say it won’t chamber a round, what exactly do you mean?

Does it pass over the round and not strip it from the magazine? Does it not strip it fully from the magazine and the round gets jammed up on its way into the chamber? Does it appear to have chambered, but the bolt doesn’t fully close/engage the lugs in the barrel extension (that one is particularly scary)?

Also, I don’t see whatever you’re trying to show in the pictures of the bolt.

Someone smarter than me should be along shortly, I’m sure.

The coating on the bolt is being blasted off by the hot gas in the bolt carrier, has
nothing to do with not being able to chamber a round.

Jdowns0415 said:

Hello snipershide, I’m back with another AR10 problem.

I had sent my barrel back to criterion to look at. They bedded the barrel, headspaced the bolt, and gave me a JP high pressure bolt. It was working fine but then suddenly with small base die Handloads and with factory hornady and FGMM ammo it simply will not reliably chamber the ammo. With duramags and PMAGS, the ammo will not chamber every other round or every couple of rounds.

I took the bolt carrier apart (fail zero bolt, JP high pressure bolt and firing pin) and I noticed this weird wear pattern on the top of the bolt. Does this mean my carrier needs to be replaced? I’m thinking maybe it somehow got damaged over the years (it has about 3500 rounds on it) but it isn’t cracked or warped and nothings loose that I can see.

Build list:
Aero M5 recievers
Rifle AR10 extension
Tubb flat wire AR10 buffer spring
KAK 5.4oz buffer
Failzero bolt carrier
JP high pressure bolt, firing pin
Geissele SSA-E
Criterion 20 inch stainless 6.5 barrel
CMT rail
Revival defense brake

Attached are pics of the bolt. Nothing seems to be warped and I can cycle the bolt just fine but ammo will not reliably chamber. I think the carrier is damaged but I wanted to get a second opinion before purchasing a rubber city or other carrier. Thanks! View attachment 8631850

Click to expand...

It's not the gases and you're not having bolt rub, I've spoke about this in a few threads on here.

JP put out a bad batch of QPQ coated bolts a while back, they are well aware of it. Call them up and talk to Dave, send it back and I'll give you a new one.

As an update to my first post, I see what you’re showing in your pictures.

Something I noticed is that you are not running the JP one piece gas rings. Is there a reason for that?

Also, regarding the gun not chambering a round, do you feel that the bcg isn’t coming far enough back to pick up the round from the magazine?

If so, does it lock back on an empty mag?

mudholestomper said:

As an update to my first post, I see what you’re showing in your pictures.

Something I noticed is that you are not running the JP one piece gas rings. Is there a reason for that?

Also, regarding the gun not chambering a round, do you feel that the bcg isn’t coming far enough back to pick up the round from the magazine?

If so, does it lock back on an empty mag?

Click to expand...

The JP one piece gas Rings or Garbage!

I stopped running them about 2 years ago and have switched to SpringCo Gas rings, I never really had any issues until I started running short barrels with exstended gas systems. Some of my Custom Builds started to become finicky with failure to feed and failure to extract for no apparent reason with random factory ammo.

I'm extremely methodical with my custom builds and one of the steps I take on all of them is the seal the gas systems.

I first noticed it with a couple of my custom 6.5 Creedmoor builds that would just dribble the case out of the ejection port with the AGB wide opened, I initially thought it was due to weak Extractor Springs but after replacing them with new SpringCo E-Springs I was met with the same results.

During the same time frame I was having the exact same issues but with more failures on a 14.5" 6ARC with Intermediate Gas System.

Since I couldn't immediately detect the cause of these failures, I assumed it was a bad lot of factory ammo.

During one of my range session I pulled the gas rings from some random builds that i was performing barrel break-in on that had the standard 3 piece gas rings, I installed them on the 6.5CM and 6ARC builds that had the complete JP Bolts.

The 3 piece rings sets immediately rectified all reliability issues. The lid on my Range Box was opened next to my daughters bench six feet away at about 4 O'clock to me and every single piece of brass both 6.5CM and 6ARC landed neatly inside. After shooting 10 round groups out of both rifles I then proceeded to walk around the range wandering around like an idiot because I couldn't find my damn brass.

when my daughter went to grab another box of ammo she yelled out, "Hey Sherlock! is this what you're looking ?" And held up a handful of brass and of course she had perfect timing when nobody was shooting so all the other range goers looked right at me and had a giggle...lol

Until about three years ago the majority of barrel manufacturers would run a larger sized Gas Port for reliability, which worked well but most of us had to resort to using adjustable gas blocks to calm down the gas.

Nowadays most quality Barrel manufacturers have put the R&D into their barrels to find the optimum size gas ports that don't require an adjustable gas block to efficiently run suppressed and unsuppressed.

Jdowns0415 said:

The magazines will feed rounds into the chamber. The bolt gets stuck about 1/4 of an inch from going all the way into battery. They extract fine once fired. If they aren’t fired it’s almost impossible to charge the bolt to the rear unless it’s mortared to the point I feel like I’m going to snap my stock or I stick a screwdriver in to pop the bolt back.

The factory ammo and small base die resized cases do this in the rifle. It’s not having double feeds or anything like that malfunction wise. The bolt locks to the rear on an empty mag no problems.

Click to expand...

List of issues i would address first

(1) Overly tight or dirty chamber, also check your Feed Ramps. ( If the Feed Ramps are rough or if you're seeing chunks of copper, polish with felt Dremel head and green polishing coumpound.)

Next perform a Drop Test, remove BCG and push a factory round into the chamber and make sure it's fully seated. Hold the complete upper barrel up and see if the round freely drops out of the chamber, if the round sticks and your chamber is clean buy a new nylon chamber brush, tightly wrap chamber brush area, not the barrel extension half with a large cotton patch.

Using KG2 or Blue JB compound fully saturate cotton patch with a few drops of CLP or Kroil Oil, using a straight and short bore specific cleaning rod and bore guide, slide brush/rod into bore guide and insert into upper so the tip is just about to make contact with the barrel Tenion. Connect the end of cleaning rod to a hand held drill set to slower speed, if you don't have a steady hand moc something up to rest the drill on so that the rod and brush stay perpendicular and steady, if you see any wobble when you start up the drill make sure your chamber brush and guide rod are perfectly straight ( when lapping a chamber for the first time it's always best to start out with a new chamber brush and cleaning rod to reduce the chances of wobble.

Carefully!!! insert bore scope in through the muzzle end and park it at the beginning of the Case Neck Area, this will prevent Over Penetration.. Giggity , engage the drill and slowly insert brush utilizing the borescope camera to monitor your depth. I do mine in 30 second intervals, after 30 seconds pull the chamber brush and bore guide out and mop out the chamber and inspect with Bore Scope. I repeat these Cycles until I see a clear Improvement in the surface area. When you feel confident that there's been a clear Improvement remove everything and thoroughly clean, perform drop test over again, rinse and repeat if issue still presents itself.

(2) Slightly Undergassed. ( If running an AGB turn up the Gas)

(3) Weak Buffer spring - underweight/overweight buffer. (If running a Large Frame Carbine System, swap the spring out with a Red SpringCo and H2 Buffer. )

Jake

Jdowns0415 said:

I had done that chamber lapping & feed ramp polishing before I sent it into criterion and with their lower the rifle was cycling fine with hornady ammo (Mike was the inspector/tester he bedded the barrel and headspaced that JP Bolt). I think the Tubb flat wire and the rifle buffer may not be strong enough to cycle the bolt despite it being the AR10 spring. I will switch back to the carbine buffer setup i have with the SCS that always cycled and see if that works. I still don't understand why the bolt would be sticking so bad on the cartridge in the chamber to extract once it gets stuck and doesn't close all the way. would that just be the spring binding? or the bolt getting jammed from spring tension?

Click to expand...

Let me get this straight...

So the drop test reliably worked with all factory ammo? And feed ramps a clean and perfectly allied?

And your our bolt is correctly head spac with fresh gas rings, with a professionally installed Barrel?

And after all that you're still getting a stuck case that you have to mortar when it doesn't properly chamber?

(1) inspect your Carrier, and Cam Pin. Also inspect your Upper Receiver with for signs of abnormal wear specifically wear around the cam pin cut out.

(2) inspect the area around the buffer retention detent pin and sides of the buffer tube and lower receiver of impact.

(3) as mentioned above, turn your Gas Up fully opened and make sure your Gas Block in properly aligned to the barrel gas port, also make sure your Gas tube isn't binding in your Gas Key of the BCG.

Remove you handguard and CH, using your finger tips slide your BCG slowly and evenly back and forth first checking for smooth chambering and Lock up, with the BCG fully chambered take a small flashlight and look under the bolt around the feed ramp area and check to make sure your bolt lugs and Barrel extension lugs are aligned properly.

The bolt lugs should perfectly align centered with the lugs of the barrel extension when chambered.

Then shift your focus to the gas tube and gas key interaction if you feel the gas key binding or making a solid impact to the gas tube you don't have proper alignment.

Keep working the BCG back and forth to the point your boat face is just making contact with the tenion don't chamber it, watch the gas tube in front of the Gas tube Port of the upper receiver, as you slide the bcg back and forth was the gas tube, it tell you which way it needs to be tweaked.

(4) lastly swap out your buffer system, if you're using the JP silent capture spring then make sure you're running the H2 tungsten model with the original spring which is the stiffest.

Jake

Jdowns0415 said:

I still don't understand why the bolt would be sticking so bad on the cartridge in the chamber to extract once it gets stuck and doesn't close all the way

Click to expand...

Sounds like headspace to me unless your cartridges are defective/improperly sized handloads.

Jdowns0415 said:

I have to legit pry the bolt with tools to get it unstuck

Click to expand...

It's either headspace or there's something stuck in your chamber or lug area, I had a popped primer get stuck in a barrel extension once

Bigjake83 said:

(1) inspect your Carrier, and Cam Pin. Also inspect your Upper Receiver with for signs of abnormal wear specifically wear around the cam pin cut out.

Click to expand...

Is this what you mean?
Possibly the cam pin gets jammed in the slot of the upper receiver? Maybe when the bolt is pushing the case or the extractor is trying to slip of the case rim?

Bigjake83 said:

The JP one piece gas Rings or Garbage!

I stopped running them about 2 years ago and have switched to SpringCo Gas rings, I never really had any issues until I started running short barrels with exstended gas systems. Some of my Custom Builds started to become finicky with failure to feed and failure to extract for no apparent reason with random factory ammo.

I'm extremely methodical with my custom builds and one of the steps I take on all of them is the seal the gas systems.

I first noticed it with a couple of my custom 6.5 Creedmoor builds that would just dribble the case out of the ejection port with the AGB wide opened, I initially thought it was due to weak Extractor Springs but after replacing them with new SpringCo E-Springs I was met with the same results.

During the same time frame I was having the exact same issues but with more failures on a 14.5" 6ARC with Intermediate Gas System.

Since I couldn't immediately detect the cause of these failures, I assumed it was a bad lot of factory ammo.

During one of my range session I pulled the gas rings from some random builds that i was performing barrel break-in on that had the standard 3 piece gas rings, I installed them on the 6.5CM and 6ARC builds that had the complete JP Bolts.

The 3 piece rings sets immediately rectified all reliability issues. The lid on my Range Box was opened next to my daughters bench six feet away at about 4 O'clock to me and every single piece of brass both 6.5CM and 6ARC landed neatly inside. After shooting 10 round groups out of both rifles I then proceeded to walk around the range wandering around like an idiot because I couldn't find my damn brass.

when my daughter went to grab another box of ammo she yelled out, "Hey Sherlock! is this what you're looking ?" And held up a handful of brass and of course she had perfect timing when nobody was shooting so all the other range goers looked right at me and had a giggle...lol

Until about three years ago the majority of barrel manufacturers would run a larger sized Gas Port for reliability, which worked well but most of us had to resort to using adjustable gas blocks to calm down the gas.

Nowadays most quality Barrel manufacturers have put the R&D into their barrels to find the optimum size gas ports that don't require an adjustable gas block to efficiently run suppressed and unsuppressed.

Click to expand...

I’ve got a JP bolt and rings in my ar10 and it runs like a scalded dog. So does the JP bolt and rings in one of my 556/223 guns. Never a single problem and both guns are easily the smoothest cycling guns I have.

Your example is so full of variables that to claim that a proven design by a high quality manufacturer is “garbage” and the reason all of your brass wasn’t landing in a nearby tool box is…ummm…yeah, call me skeptical.

What did JP tell you when you told them this story?

mudholestomper said:

I’ve got a JP bolt and rings in my ar10 and it runs like a scalded dog. So does the JP bolt and rings in one of my 556/223 guns. Never a single problem and both guns are easily the smoothest cycling guns I have.

Your example is so full of variables that to claim that a proven design by a high quality manufacturer is “garbage” and the reason all of your brass wasn’t landing in a nearby tool box is…ummm…yeah, call me skeptical.

What did JP tell you when you told them this story?

Click to expand...

Okay Junior go back and focus on your reading comprehension and reread my post in it's entirety.

Now let me grab some crayons and see if I can color this out for you so you can understand the topic at hand.....

Obviously you don't know me or what I do.
I probably own more JP Rifles than anybody on the Hide and have conducted many reviews on their Rifles and individual parts, I have done a unrecollable amount of custom builds utilizing JP products and complete rifles since 2007.

I'm not even trying to boast these are just the facts.

JP has been having QC issues off and on for a while now with their QPQ Coating and Gas Rings specs, I've spoke with Dave several times about these issues.

Two months ago I had to send in a Grendal Bolt and a HP .308 bolt for Warranty replacement for these very same reasons, I built a couple High End Precision Uppers for customers and had to replace their Bolts because after one range Session the QPQ coating came off.

The fact is there isn't a Firearms Manufacturer on this planet that hasn't had QC problems from time to time , Shit happens!!.

The issue and why one piece Gas Ring sets are Garbage!! Is because like most firearm parts they have to be within a certain spec, and if QC falls off just little reliability starts to suffer and if One Piece Rings fall out of spec you're going to have failures plain and simple.

But do you know what has a extremely wide effective operational window???

That's right the good old fashion 3 piece gas rings design! Quality 3 piece gas ring sets and one piece gas rings are all disposable wear parts with a lifespan.

A few years ago I was helping a buddy through his first local PRS Gas Gun Match, on the 3rd stage he started to have failures to extract. After doing a quick cleaning and inspection I saw that his Gas Rings were basically smoked, not having any spare gas rings on me cuz I wasn't competing that day I removed his gas ring from the bolt stretch them out, reinstalled them and he finished the match with 100% reliability.. let me see somebody do that with a JP one piece gas ring....

Nuff said!..

Bigjake83 said:

Okay Junior go back and focus on your reading comprehension and reread my post in it's entirety.

Now let me grab some crayons and see if I can color this out for you so you can understand the topic at hand.....

Obviously you don't know me or what I do.
I probably own more JP Rifles than anybody on the Hide and have conducted many reviews on their Rifles and individual parts, I have done a unrecollable amount of custom builds utilizing JP products and complete rifles since 2007.

I'm not even trying to boast these are just the facts.

JP has been having QC issues off and on for a while now with their QPQ Coating and Gas Rings specs, I've spoke with Dave several times about these issues.

Two months ago I had to send in a Grendal Bolt and a HP .308 bolt for Warranty replacement for these very same reasons, I built a couple High End Precision Uppers for customers and had to replace their Bolts because after one range Session the QPQ coating came off.

The fact is there isn't a Firearms Manufacturer on this planet that hasn't had QC problems from time to time , Shit happens!!.

The issue and why one piece Gas Ring sets are Garbage!! Is because like most firearm parts they have to be within a certain spec, and if QC falls off just little reliability starts to suffer and if One Piece Rings fall out of spec you're going to have failures plain and simple.

But do you know what has a extremely wide effective operational window???

That's right the good old fashion 3 piece gas rings design! Quality 3 piece gas ring sets and one piece gas rings are all disposable wear parts with a lifespan.

A few years ago I was helping a buddy through his first local PRS Gas Gun Match, on the 3rd stage he started to have failures to extract. After doing a quick cleaning and inspection I saw that his Gas Rings were basically smoked, not having any spare gas rings on me cuz I wasn't competing that day I removed his gas ring from the bolt stretch them out, reinstalled them and he finished the match with 100% reliability.. let me see somebody do that with a JP one piece gas ring....

Nuff said!..

Click to expand...

I love your enthusiasm and I always appreciate it when an old head shares what they know. I’d love to see some of your collection.

Despite your compelling argument (and spirited typing skills), I will agree to disagree that the JP one piece gas rings are “garbage” or that their mere presence makes a gas system less efficient or reliable, or that they are a hindrance to an otherwise well gassed, good running rifle.

Now back to Daddy Trump’s speech…

mudholestomper said:

I always appreciate it when an old head shares what they know. I’d love to see some of your collection.

Click to expand...

I'm sure you would, and I'm 41 Dick!...lol

Bigjake83 said:

I'm sure you would, and I'm 41 Dick!...lol

Click to expand...

Lol I’m 9 years older than you .

Being an old head refers to experience, not age.

Now get back in your lane, youngster!!