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View Full Version : Removing flash hider from CMMG upper


creampuff
03-12-2007, 1:57 AM
I notice a large number of questions on how to remove the flashhider from the upper. It really is pretty easy, so I am not sure why I am posting this...oh well...here it goes.

Two words of caution:
1. If your barrel is less than 16 in (ie 14.5 in), don't try this !!! Your barrel probably has a permanently mounted flashhider. Nothing good can come from this is you try to remove it with a wrench.
2. I know CMMG fastens their flashhider with standard threads. I can't remember which company uses a reverse thread. Make sure your upper does not have reverse threading, unless you want to ruin the threads on your barrel.

What do you need:
A wrench.
A vise.
A barrel vise.
http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=608967.

Midway sells them for around $15. There are plenty of uses for a receiver vise...this isn't one of them. You don't want to mess up the indexing on your upper. Get a barrel vise.

http://i76.photobucket.com/albums/j36/creampuff464/DSC_4729.jpg


If you can't wait, then get a pair of calipers, measure the outside of the barrel where you will be clamping it, and then get some scrap wood. If the wood is too soft, it might not grab. Clamp them together, it will torque when you drill it, so clamp on all four sides. Drill a hole, somewhat smaller than the outside diameter of the barrel; in my case 5/8" spade bit works.
You will end up using these two pieces of wood, like you would the barrel vise.

http://i76.photobucket.com/albums/j36/creampuff464/DSC_4723.jpg



For my CMMG heavy barrel, and government contour barrel, I ended up using the smaller holes on the barrel vise. Notice how I didn't cover it with leather or some soft but durable material. That was a mistake for this demo. I ended up marring the barrel. Don't make my mistake, use some leather or electral tape to wrap the barrel.

http://i76.photobucket.com/albums/j36/creampuff464/DSC_4725.jpg

Lastly, left loosie, rightie tightie for the CMMG uppers. Get a big ole' crescent wrench, the little ones won't generate enough torque. The flash hiders have a wrench flat, so the wrench shouldn't have any problems grabbing hold of the hider.

http://i76.photobucket.com/albums/j36/creampuff464/DSC_4728copy.jpg

That's it. If you use one of the midway threaded protectors to replace, the FH, you just need hand tightening, no tools. I haven't replaced the FH with a muzzle brake, so I don't know anything about indexing a FH or brake with the barrel. If anyone has any input on that feel free to tack onto this thread.

Now I am off the reblue the portion of the barrel I marked up doing this demo.

FinweElensar
03-12-2007, 8:35 AM
Isn't the flash hider pinned and welded? Don't you have to remove the pin first?

SigShooter
03-12-2007, 9:15 AM
I haven't replaced the FH with a muzzle brake, so I don't know anything about indexing a FH or brake with the barrel. If anyone has any input on that feel free to tack onto this thread.

Now I am off the reblue the portion of the barrel I marked up doing this demo.

Thanks, nice walk through.

If anyone has input on how to index a muzzle break, please share. I had to replace a FH on a RRA upper I got from CWS at the Cow Palace show on Sat and I am having a bear of a time getting the bottom of the MB to line-up with the bottom of the barrel when using the new crush washer. I wind up being almost a full turn away every time. (will a crush washer "crush" that far?) I wound up using the crush washer that was on there with the FH and was able to get it to about 1/4 turn away.

Thanks again...

creampuff
03-12-2007, 9:16 AM
Isn't the flash hider pinned and welded? Don't you have to remove the pin first?

Not on a CMMG upper (>16 in barrel); if it was less than 16 inch barrel, then yes it would have to be a pinned and welded, or fixed in some permanent way.

shark92651
03-12-2007, 9:24 AM
The best way to get the muzzle brake to align properly is to hand tighten the brake until the side you want aligned at the bottom is at the 3 o'clock position. If not, use a file and file down the back side of the crush washer a little at a time, re-checking the hand tightened position until the side you want on the bottom is at 3 o'clock. Then, use a wrench to tighten it down to the 6 o'clock position.

SigShooter
03-12-2007, 9:29 AM
The best way to get the muzzle brake to align properly is to hand tighten the brake until the side you want aligned at the bottom is at the 3 o'clock position. If not, use a file and file down the back side of the crush washer a little at a time, re-checking the hand tightened position until the side you want on the bottom is at 3 o'clock. Then, use a wrench to tighten it down to the 6 o'clock position.

AHHH!! I may try that one. On a side note, is there any harm re-using the crush washer that was on there with the FH if there was no visible damage or excessive wear?

shark92651
03-12-2007, 4:41 PM
I don't think there is any problem with using the existing washer as long as it still has a convex/concave shape.