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Posted: 2/25/2015 3:15:01 PM EDT
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I bought a CMMG rifle a year ago and have been using a 1-4x scope on the upper receiver. I want to train with my new iron sights so I took the scope off. I noticed that the hand guard was not in line with the upper and this will affect the sight alignment since the front and rear sights are mounted to separate parts. The hand guard was slightly canted and I could feel the edge of the top rail where it protruded out from the receiver rail. Also, this is a 15" hand guard so I could see a change in angle at the connection point. I checked and there was a gap at the bottom and flush at the top so that put the front sight above alignment. Of course I could adjust the sights but first I want the rails aligned. I loosened the two retaining screws and realigned the hand guard. Before I tightened the screws, I attached my one piece scope mount where it would hold the two parts together.
After this adjustment it looked good. There was no catch where the two rails met. So I went out in the rain and blasted 28 rounds and they all hit target. When I cam in I inspected the rails and the hand guard was off again, not visibly but I can feel the overhang between the two rails again. I cranked down on the screws tight. Should I Lock-Tight it next time? This is my fore end |
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Quoted:
I bought a CMMG rifle a year ago and have been using a 1-4x scope on the upper receiver. I want to train with my new iron sights so I took the scope off. I noticed that the hand guard was not in line with the upper and this will affect the sight alignment since the front and rear sights are mounted to separate parts. The hand guard was slightly canted and I could feel the edge of the top rail where it protruded out from the receiver rail. Also, this is a 15" hand guard so I could see a change in angle at the connection point. I checked and there was a gap at the bottom and flush at the top so that put the front sight above alignment. Of course I could adjust the sights but first I want the rails aligned. I loosened the two retaining screws and realigned the hand guard. Before I tightened the screws, I attached my one piece scope mount where it would hold the two parts together. After this adjustment it looked good. There was no catch where the two rails met. So I went out in the rain and blasted 28 rounds and they all hit target. When I cam in I inspected the rails and the hand guard was off again, not visibly but I can feel the overhang between the two rails again. I cranked down on the screws tight. Should I Lock-Tight it next time? This is my fore end Yes. I personally use blue loctite for that application. |
| I have never been a huge fan of this style of fore end retention for this reason. I would re-install the screws with loc tite. I keep blue on my bench for this kind of stuff. I don't know if they give any information on how much those screws should be torqued but I would get them nice and tight with the blue stuff on and let it do its job. |
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I have never been a huge fan of this style of fore end retention for this reason. I would re-install the screws with loc tite. I keep blue on my bench for this kind of stuff. I don't know if they give any information on how much those screws should be torqued but I would get them nice and tight with the blue stuff on and let it do its job. Right after I posted this, I contacted CMMG. I got a response the same day. Justin at CMMG did not ask any questions. He told me to send him a picture of the connection point along with my shipping address. Next day he said the part is on the way out. I didn't buy this rifle directly from CMMG and am not even registered with them and they stand behind the product. Best service I have ever seen in any industry. I'll let you know if they send out an identical part or if they have made some modifications. Might be why he wanted a picture to see if I had a mod part or original. The aluminum is getting wallered out each time I tighten the bolts. I would like to use some sort of retaining compound where it slides onto the barrel nut sleeve but I am concerned about disassembly in the future. Loctite blue is for threads but I was thinking about loctite green or 3m makes a product for this application but they seem permanent. Edit: That was fast! I emailed CMMG Asking about installing the new part. Before I posted the above, he responded saying this: "Yes you should receive a vial of green loctite in the kit when it arrives. Just put two lines of that loctite down the outside of the barrel nut on each side of the gas tube then also on the ends of the T25 screws and you should be good to go." Fabulous! |
| Go sparingly on that green shit (this is exactly what the stuff was made for, slip fit retention not thread locking and it does it exceedingly well), once those screws are tightened down and it sets it should definitely not move anymore. Also use blue on the screw threads. |
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Go sparingly on that green shit (this is exactly what the stuff was made for, slip fit retention not thread locking and it does it exceedingly well), once those screws are tightened down and it sets it should definitely not move anymore. Also use blue on the screw threads. Yeah I was afraid the barrel nut and hand guard will become one unit. Depending on what specific green stuff it is, it may break free only after heating above resistance. |
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Go sparingly on that green shit (this is exactly what the stuff was made for, slip fit retention not thread locking and it does it exceedingly well), once those screws are tightened down and it sets it should definitely not move anymore. Also use blue on the screw threads. Hey where did you hear it was for slip fitting a handgauard to a barrel nut? I'm curious because JPRifles set me up for use as a thread locker for an adjustable gas block. Yes, the screw threads for the clamp on JP adjustable gas block. Ttheir service dept. did not recommend it as a slip joint adhesive in referrence to the slip fit of the barrel in relation to the inner diameter of the gas block. I have since removed it without too much trouble after a bit of the heat gun treatment. Thanks 
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Quoted:
Hey where did you hear it was for slip fitting a handgauard to a barrel nut? I'm curious because JPRifles set me up for use as a thread locker for an adjustable gas block. Yes, the screw threads for the clamp on JP adjustable gas block. Ttheir service dept. did not recommend it as a slip joint adhesive in referrence to the slip fit of the barrel in relation to the inner diameter of the gas block. I have since removed it without too much trouble after a bit of the heat gun treatment. Thanks
Quoted:
Quoted:
Go sparingly on that green shit (this is exactly what the stuff was made for, slip fit retention not thread locking and it does it exceedingly well), once those screws are tightened down and it sets it should definitely not move anymore. Also use blue on the screw threads. Hey where did you hear it was for slip fitting a handgauard to a barrel nut? I'm curious because JPRifles set me up for use as a thread locker for an adjustable gas block. Yes, the screw threads for the clamp on JP adjustable gas block. Ttheir service dept. did not recommend it as a slip joint adhesive in referrence to the slip fit of the barrel in relation to the inner diameter of the gas block. I have since removed it without too much trouble after a bit of the heat gun treatment. Thanks
Justin at CMMG said to use it. I told him about my handguard shifting Friday and a new part will get here Tuesday with a vial of Loctite Green. My handguard contacts the the barrel nut sleeve in four places so I will put a thin line at those spots. Then I will take care not to clamp down too tight on the bolts to keep from from reaming the aluminum. |
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Just got the new RKM hand guard. As suspected, CMMG is replacing the original hand guard with one that has been redesigned. The tabs that contain the retaining bolts are thicker, making the gap smaller. I have yet to install it but I imagine that it is going to be machined to tighter tolerances with the barrel nut. The installation instructions suggest a rubber mallet to aid in installation. I expect it to be tight and difficult to get on.
See the difference? |
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