Want to build a Dissipator upper. Am looking at a S&W M&P15 on a local forum that has a 16in melonited 5R heavy barrel (no M4 cuts).

My question is, on these barrels, what is the diameter between the front sight and the muzzle? I'm trying to see if I can add a clamp on FSB at rifle length position.

Thanks in advance.

Standard heavy barrel FSBs are .750.

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Hold my beer and watch this!

Right, I expected .750 under the carbine length FSB that's on there stock.

I'll be cutting that down so a rifle length handguard goes over it. And putting a second FSB (no gas to it) at the rifle length position to hold the front of the rifle handguard and give me rifle length sight radius.

So what I am trying to find is what diameter is the barrel further up where I'll be putting the new/second FSB. Maybe there isn't any step down and it is .750, I don't know....

I thought it was .740?

Thanks. IF its .750 under the FSB, then .740 is what I would have guessed. Hoping someone with a Sport or other model with the 5R barrel has digital calipers to check for certain.

I just measured my Sport and it's .740 from the FSB to the muzzle.


-Bill

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- Bill

EXCELLENT. Thanks everybody!

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