PDA

View Full Version : AR-15 Flash suppressor removal causing front sight rotation.


fatmanforprez
07-08-2009, 9:29 PM
I hope this isn't covered elsewhere, I did some searches but found nada. I am kind of a newbie to AR-15 clones as well as this forum in general so pardon my ignorance.

I have a CMMG upper I recently acquired with an A2 device (I just read enough threads that I don't care to name it) on the muzzle. The barrel is 16" so my understanding is it should not be pinned and welded, though I am considering this as an option because I have heard they can hide these things and my difficulties have been numerous.

I put my upper in a vice block (a Model 1 Sales upper block [no thats not the source for the upper]), applied counter clockwise force to the A2 device, and my front sight base visibly rotated (counter clockwise of course). I was able to turn the A2 device clockwise and the whole shebang righted up (didn't remove the A2 device though, obviously).

Now my understanding is this is not the way it works, there was nothing touching the front sight base, and it moved with the barrel that should not be rotating either. It should be noted that my gas tube did not seem disturbed and my bolt has no problem seating over the gas tube. Though these are hardly scientific, though no one would mistake the FSB for being anything but crooked in that position (probably 10-15 degrees from level at it's worst).

This makes me think the barrel itself rotated in place, I did not think this possible, and am not sure how worried I should be about this.

Has anyone bought a CMMG flat-top upper with a 16" barrel marked "CMMG WASP 5.56 NATO 1/9" that can tell me if it is pinned and welded?
Has anyone seen something like this before?
How worried should I be?
What can I do to safely get that A2 device off?

technique
07-08-2009, 9:33 PM
Uhhhh....you may have cracked your upper where the barrel meets the receiver.

Or it may have come that way....I have seen one CMMG come from them like that....they over cranked it.

Either way...take it all the way down and inspect it. DANGEROUS!

xr650r
07-08-2009, 9:38 PM
clamp the barrel, not the upper receiver.

Brutish
07-08-2009, 9:42 PM
I hope this isn't covered elsewhere, I did some searches but found nada. I am kind of a newbie to AR-15 clones as well as this forum in general so pardon my ignorance.

I have a CMMG upper I recently acquired with an A2 device (I just read enough threads that I don't care to name it) on the muzzle. The barrel is 16" so my understanding is it should not be pinned and welded, though I am considering this as an option because I have heard they can hide these things and my difficulties have been numerous.

I put my upper in a vice block (a Model 1 Sales upper block [no thats not the source for the upper]), applied counter clockwise force to the A2 device, and my front sight base visibly rotated (counter clockwise of course). I was able to turn the A2 device clockwise and the whole shebang righted up (didn't remove the A2 device though, obviously).

Now my understanding is this is not the way it works, there was nothing touching the front sight base, and it moved with the barrel that should not be rotating either. It should be noted that my gas tube did not seem disturbed and my bolt has no problem seating over the gas tube. Though these are hardly scientific, though no one would mistake the FSB for being anything but crooked in that position (probably 10-15 degrees from level at it's worst).

This makes me think the barrel itself rotated in place, I did not think this possible, and am not sure how worried I should be about this.

Has anyone bought a CMMG flat-top upper with a 16" barrel marked "CMMG WASP 5.56 NATO 1/9" that can tell me if it is pinned and welded?
Has anyone seen something like this before?
How worried should I be?
What can I do to safely get that A2 device off?


You already screwed up by clamping the upper receiver in a vise and not the barrel. You may have damaged your receiver.

The proper way to set up the upper for removal of the muzzle device is to put the barrel in a barrel vise and then remove the muzzle device.

I hope you didn't hurt your upper receiver.

AlliedArmory
07-08-2009, 9:50 PM
clamp the barrel and not the receiver. Use towels in the vise if you don't have a proper barrel vise.

hopefully you didn't damage your receiver

fatmanforprez
07-08-2009, 10:08 PM
Thanks, I knew something was wrong, now it seems such a stupid mistake to make. Thanks for all your assistance guys. I am gonna go see if I need a new upper.

rabagley
07-08-2009, 11:26 PM
If your upper is damaged, just order the bare upper for about $100 and transfer everything over.

Fate
07-09-2009, 9:23 AM
I use two scrap pieces of 1/8" thick leather to pad my FSB and clamp that in the vise when swapping out muzzle devices. Works great and no barrel rotation issues.

Sorry to hear that you might've messed up your upper.

ar15barrels
07-09-2009, 11:03 AM
Sounds like the barrel nut is not very tight or it's indexed at the minimum of the torque range.
It's always better to clamp the barrel if possible, but in most cases, simply removing or installing a muzzle device does NOT cause sight bases to move.

shark92651
07-09-2009, 1:03 PM
I hope this isn't covered elsewhere, I did some searches but found nada. I am kind of a newbie to AR-15 clones as well as this forum in general so pardon my ignorance.

I have a CMMG upper I recently acquired with an A2 device (I just read enough threads that I don't care to name it) on the muzzle. The barrel is 16" so my understanding is it should not be pinned and welded, though I am considering this as an option because I have heard they can hide these things and my difficulties have been numerous.

I put my upper in a vice block (a Model 1 Sales upper block [no thats not the source for the upper]), applied counter clockwise force to the A2 device, and my front sight base visibly rotated (counter clockwise of course). I was able to turn the A2 device clockwise and the whole shebang righted up (didn't remove the A2 device though, obviously).

Now my understanding is this is not the way it works, there was nothing touching the front sight base, and it moved with the barrel that should not be rotating either. It should be noted that my gas tube did not seem disturbed and my bolt has no problem seating over the gas tube. Though these are hardly scientific, though no one would mistake the FSB for being anything but crooked in that position (probably 10-15 degrees from level at it's worst).

This makes me think the barrel itself rotated in place, I did not think this possible, and am not sure how worried I should be about this.

Has anyone bought a CMMG flat-top upper with a 16" barrel marked "CMMG WASP 5.56 NATO 1/9" that can tell me if it is pinned and welded?
Has anyone seen something like this before?
How worried should I be?
What can I do to safely get that A2 device off?

You can bring it by our shop in Costa Mesa if you want us to take a look at it for you.