I still have the stock fore-end grip and like this idea for a light mount. Any experience with it?

Amazon.com: Elzetta Front Sight Base Flashlight Mount for AR15, M16, and M4, Quick-Release Thumb Screw Model: Sports & Outdoors

No experience with one, but the reviews look promising.
I would have two concerns: 1) barrel harmonics - how would it effect accuracy? This wouldn't be an issue if it's strictly a mid to short range defense weapon. 2) I'd prefer something that is quick release. That's just my preference.

I have this on my M&P. I like it because I like to keep the gun slim with nothing hanging off the sides (like most light mounts). No noted affect on accuracy. It does not clamp to the barrel, but the front sight A frame and bayo lug. I put a Surefire 6P with LED in it.

If u want to keep it slim, put a 4 lug rail on the bottom of the hand guard, then get any flashlight and mount u want.
I would be a little concerned with weight hanging on the sure post.
JMO.

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