Could this cause accuracy and consistency issues in an AR10?

[old11bravo]

Well I think I may have finally figured out why I'm not getting the consistency and/or accuracy out of my Mega Maten AR10 build. I was blaming it on a bad Mega barrel until recently. I was removing the muzzle brake because I wanted to try something different and I discovered this!

It looks like a crusty carbon build up has been deposited on the inside of the brake threads. I tried cleaning/removing this metallic concrete type of cruddy build up out of the threads but nothing I've done so far has been successful. I believe this build up occurred because I used a jamb nut to secure the brake to the muzzle of the barrel rather than threading the brake all the way on to the muzzle until it seated flush against the crown of the barrel. The jamb nut effectively left a void section of threads on the inside of the brake. Anyway, that is my theory. Please see the pictures below and tell me what you think.

QUESTIONS.....?

Do you think this deposit occurred because the brake wasn't seated flush with the crown of the barrel (due to using a jamb nut)?

Do you think this crud build up is significant enough to affect and diminish the accuracy of the barrel?

I noticed some of the carbon crud build up on the crown as well. The picture shows a lot of fibers from the cloth I wiped it with so please disregard those. Does the crown of the barrel look like it will be okay for me to install a new brake?

Anyone have any ideas for methods, products or tools that would remove the carbon crud build up seen in the pictures?

I've always held the Mega brand in high regard but became very disappointed with this barrel sometime last summer. It started out satisfactory enough but I wouldn't consider it satisfactory now. The specs on the barrel are listed below the pictures.







Mega 308 Barrel – 18 - $310 ($294.50)
• Manufactured under the strict supervision of Mega Arms.
• Chambered in .308 Winchester
• Machined with a Medium Contour.
• 1:10 twist for accurate overall performance.
• 5/8-24 threaded muzzle.
• .750 diameter gas block seat.
• SR-25/DPMS pattern barrel extension.
• 11° target crown.
• Uses standard AR-15 Mid Length Gas system.
• GUARANTEED TO SHOOT SUB 1 MOA @ 100 YARDS WITH MATCH AMMO!!
• Made from 416 Stainless Steel
• Finished in Black Nitride Coating
• Weight 44.4 oz

Read More

 

[Kruel J]

The bullet shouldn't be touching (and isn't per the pictures) any part of the break. I'm gonna vote no. Have you looked at the crown to make sure its free of any defects?

 

[oli700]

QUESTIONS.....?

Do you think this deposit occurred because the brake wasn't seated flush with the crown of the barrel (due to using a jamb nut)? Yes and no . The gap is common unless you use rockset..... allowing no spacer .

Do you think this crud build up is significant enough to affect and diminish the accuracy of the barrel?
not on the threads

I noticed some of the carbon crud build up on the crown as well. The picture shows a lot of fibers from the cloth I wiped it with so please disregard those. Does the crown of the barrel look like it will be okay for me to install a new brake?
Slightly maybe.... depends if your talking a half inch at 200 yards or several inches..... doesn't look too bad to me but it's not adding accuracy that's for sure . Scrape the carbon carefully or get some amp is bas d cleaner like Barns or another copper/carbon killer or combination of the two... might be layers

Anyone have any ideas for methods, products or tools that would remove the carbon crud build up seen in the pictures?

I've always held the Mega brand in high regard but became very disappointed with this barrel sometime last summer. It started out satisfactory enough but I wouldn't consider it satisfactory now. The specs on the barrel are listed below the pictures.
Should be a good barrel but no one is perfect

 

[old11bravo]

The bullet shouldn't be touching (and isn't per the pictures) any part of the break. I'm gonna vote no. Have you looked at the crown to make sure its free of any defects?

Isn't that the crown in the last picture? What am I looking for? If that is the crown, there is some carbon build up on the surface that faces the front of the rifle. Can you see it?

 

[Kruel J]

Isn't that the crown in the last picture? What am I looking for? If that is the crown, there is some carbon build up on the surface that faces the front of the rifle. Can you see it?

It is. Hard to tell, but any defects, low spots, high spots, burrs, or anything else that isn't uniform.

 

[Kruel J]

The threads of your break are so far away from the bullet's travel path that they should have ZERO effect on accuracy. Let me ask this, what glass and mount are you using? Is the mount ONLY on the receiver rails or is it splitting the gap to the hand guard? Did you lap the mount/rings? Checked that it's tight? Torqued properly? Tried different weight bullets? Different projectile types? I ask because I had this happen with an RPR and after having my one piece mount professionally lapped and using 168 grain Sierra Matchking ammo I figured out what made it shoot like it should.

 

[old11bravo]

Started out with a US Optics MR10 in a Badger mount. Currently using this in a Bobro mount .....

Never had either lapped. Not really even sure what "lapped" means although I've heard the term plenty.
I've tried many, many, many different types of factory ammo (I don't reload), both match and cheap stuff.

 

[oli700]

It could be a great many things... you're running good gear and that carbon isn't much.

 

[Member 34319]

Simple solution.

Shoot it without the brake.

Honestly though. So many things factor in accuracy.

Only a handle factors in precision.

Start eliminating the factors for accuracy and you'll see if it is in fact a factor of precision.

 

[oli700]

I would look at copper fouling

 

[DirectDrive]

Simple solution.

Shoot it without the brake.

This ^^^
That's the first thing I would do.
If nada, then you might want a GS to check the muzzle ID and crown.

Then the brake and that jamb nut.
How tight are you torquing it ?

Muzzle devices are not favored on competition rifles.
The last couple of inches of the barrel and its crown are sacred territory.
Just the act of threading a muzzle can cause it to swell.
Machinists/gunsmiths have measured this.

USGI torque spec for the flash hider with crush washer is 15-20 ft lbs
So you don't want to go Full Bubba with your torque at the muzzle device.

Good Luck

 

[Kruel J]

Started out with a US Optics MR10 in a Badger mount. Currently using this in a Bobro mount .....
View attachment 457733
Never had either lapped. Not really even sure what "lapped" means although I've heard the term plenty.
I've tried many, many, many different types of factory ammo (I don't reload), both match and cheap stuff.

Super long thread, but maybe worth a read?

RPR .308 accuracy issues RESOLVED

 

[Ura-Ki]

I have run into the exact same issues, bolt actions and semi's alike, the Problem I have found, most breaks are ether not threaded deep enough, or the barrel threads are not set back enough to match the break! I took my last bolt action apart and discovered that as the round count went up, so did the carbon build up, and is acts sort of like a false crown ( if that makes any sense) basically its by passing the rifles original crown, creating a void for deposits to build up, and then disrupting the air which should be as smooth and uniform as possible. This particular rifle was set up with a Vortex long 3 prong flash hider, and I set the barrel threads back to close the gap, and removed the rifles crown, making the inside of the flash hider ( same idea with a break) into the crown between the prongs! My accuracy issues went away once this was done! I just did this on my FAL and it also made a difference!

 

[Kruel J]

I have run into the exact same issues, bolt actions and semi's alike, the Problem I have found, most breaks are ether not threaded deep enough, or the barrel threads are not set back enough to match the break! I took my last bolt action apart and discovered that as the round count went up, so did the carbon build up, and is acts sort of like a false crown ( if that makes any sense) basically its by passing the rifles original crown, creating a void for deposits to build up, and then disrupting the air which should be as smooth and uniform as possible. This particular rifle was set up with a Vortex long 3 prong flash hider, and I set the barrel threads back to close the gap, and removed the rifles crown, making the inside of the flash hider ( same idea with a break) into the crown between the prongs! My accuracy issues went away once this was done! I just did this on my FAL and it also made a difference!

This guy knows what he's talking about!

 

[v0lcom13sn0w]

i used to use jam nuts on all my AR barrels. never had a problem and yea my brakes built up carbon too