Ok, I have an issue. I bought my M&P 10 last year and noticed that the MOE hand guard did not completely close together at the receiver side. Under recommendations by different Forum readers, I took a my Dremel to the hand guard and ground off the little nubs inside the hand guard that are suppose to index with the barrel nut.

This weekend, I picked up new MOE M-Lok hand guard and am having the same issue. Further investigation, it appears that the gas tube is not indexed in the center of the teeth of the barrel nut. This would explain why the MOE hand guards will not fit properly.

My question is:

1. What size barrel nut wrench do I need for this rifle? Is it just a standard AR15 barrel nut wrench or something proprietary to S&W?

2. Can I used this wrench and tighten the barrel nut just enough to get the gas tube to index properly in the barrel nut or will this over tighten the barrel nut too much?

3. Should I just take it to a gun smith and let him/her deal with it?

4. Should I just grind out the indexing tabs of the new MOE M-Lok hand guard and call it good?

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That is just wrong. Hopefully you can run the nut down a bit more but you need to set the upper in a vice block setup to do it. They do use standard AR wrench.

spud83672: Ok, I have an issue. I bought my M&P 10 last year and noticed that the MOE hand guard did not completely close together at the receiver side. Under recommendations by different Forum readers, I took a my Dremel to the hand guard and ground off the little nubs inside the hand guard that are suppose to index with the barrel nut.

This weekend, I picked up new MOE M-Lok hand guard and am having the same issue. Further investigation, it appears that the gas tube is not indexed in the center of the teeth of the barrel nut. This would explain why the MOE hand guards will not fit properly.

My question is:

1. What size barrel nut wrench do I need for this rifle? Is it just a standard AR15 barrel nut wrench or something proprietary to S&W? Uses the same wrench as an AR15.

2. Can I used this wrench and tighten the barrel nut just enough to get the gas tube to index properly in the barrel nut or will this over tighten the barrel nut too much? How much torque is on it now?

3. Should I just take it to a gun smith and let him/her deal with it? Your call if (4) below doesn't help.

4. Should I just grind out the indexing tabs of the new MOE M-Lok hand guard and call it good? Don't grind the tabs. This keeps the hand guard (HG) from rotating/twisting. You may need to shave material off the HG square where it meets the barrel nut. A pic would help here. (going by memory here) There is a slot where the barrel nut teeth sit it. I had a barrel nut on another rifle where it was on the +high side of the tolerances. HG would not go on without removing an 'RCH' of material.

I just got a wrench from Brownells markets as fitting AR10 rifles. I never tried others made for AR15s to see if they are the same.

Thanks everyone! I solved my problem. Took the rifle down to "Get Some Guns" and had them turn the barrel nut one notch and fit the new MOE M-Lok hand guard on. I'm a happy camper now!!

My modifications (I think) are complete for now.

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