im trying to decide which quad rail and size that I want to go with for my AR. If I was go with a 12 inch rail, what extra parts would I need to buy to install ?

It depends somewhat on how the gun is currently configured and which rail you buy. I put a longer free-float quadrail on mine and all I had to buy was the low-profile gas block. Oh, I also had to buy an armorers wrench to remove the barrel and flash suppressor, a punch set to remove the gas block and gas tube pins, and a vise block set to hold the receiver while I removed the barrel.

Ok so I do need to order a new gas block for sure

Are you going to get one of the multi-piece rails that don't require disassembly? If you buy one of the "screw-on" types that come with their own barrel nut, you will need an armorer's wrench to remove the existing barrel nut. Some of these are REALLY tight, too. Don't even think of removing this nut without clamping it securely using a vise block. In order to change the gas block, you will need to remove the flash suppressor. You might be able to do this with the right size open-end wrench. Having the proper punches to remove the gas block/tube pins helps greatly. Do you have access to these tools? It's not a complicated job but it really helps to have the right tools!

What M&P do you have? If you have an OR with a rail height gas block, then yes, you need to get a low pro gas block. If you have a front sight post then you have the option to replace it with a low pro gas block or cut the sight post down into a low profile. Either works. If it was me, I'd cut it down. Then you would have to cut off your delta ring and spring as well.

If your going for the look of the 15T, Leapers makes the hand guard used on the 2nd generation T's. You will need a low profile gas block to use this rail system. I have not used an aftermarket handguard from them, but I would think that if you ordered one it would have everything you need for an install.

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15T,15-22,5946 & some not S&W

If you are going to free float go with a Troy Alpha rail. You can place rail segments where you need them and keep the rest of ur handguard clear to hold on to. I would say go as long as you can.

I was looking at the Troy BattleRail Bravo, just not sure what length will be good. Im going to have to wait till I have my riffle in hand from the FLL before I determine that I guess.

OP what rifle did you get in the first place? Does it have a front sight base?
If so I would look into handguards that use the factory barrel nut instead of a proprietary barrel nut, but that is how I feel and it can limit your choices. Not sure about the bravo rails but IIRC the alpha rail uses the factory barrel nut.

I myself had a carbine length gas system with a front sight base, and I chose a rail that did not require removal of the FSB or delta ring.

Free Float with "NO modification"

Mine is the delta rail, but they make a charlie that is the same thing but is a quad rail rather than a mono rail style

I removed my fsb's and put on micro YHM gas blocks. Then I went with full free floating rifle length tubular rails with the ability to put rail segments anywhere. I just dont use them anywhere but the top and a bottom short one for a bipod.

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Grover Oathkeeper

Consider the Samson Evolution, it uses the stock barrel nut.

Sent from my DROIDX

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Improvise, Adapt, Overcome

I too, am looking to modify my M&P (sport model, 16") with a quad rail and have done a fair amount of research online. After looking at a LOT of rails, the one-piece rifle length (12"–13") seems to be the one I keep going back to, even though I don't see very many examples out there. Yankee Hill looks great, but I'd like to stay with the existing barrel nut. Troy looks good too and fits well into my budget, but I'd like a continuous rail for optic placement.

The low profile gas block I have will take care of the carbine gas tube issue and provide a nice clean look (much like the M&P15T). Does anyone know which company provides the rails for the M&P15T and do they have a 12"–13" version? Any suggestions would be terrific!

My 15T is a couple years old but the Quad Rail on it is a Troy. It has a continous mounting surface and uses an AR Barrel Nut.

I am looking for the same thing for my .204 Ruger Upper. It has a Rifle Length Gas System and I need an extended rifle Quad Rail to hide the Gas Block and .936" turned area on the barrel.

nitewatchman

I have an M&P 15 MOE edition. I used this rail:

556 Tactical Evolution Rail Series 12.37"

It is an awesome rail. I had to take off the A2 front site block (Craftsman 6 pc roll punch set, $15). I used a YHM low profile gas block (Primary arms). I removed the D ring with my dremel. I removed the flash hider using a cresent wrench. The rail comes with a thermal bushing that goes around the stock barrel nut and locks the rail in place. It comes with three rail sections you can mount to the rail. The rail is solid, the rifle was easily modified to make the rail fit. Love it. It is a Samson Evolution rail with some modifications.

I agree, good looking rail and this is along the lines that I have been looking for. I think that I will see if I can meet one in person locally. The 12.37" may work and the 15" would be just right on my 24" barrel.

nitewatchman

That 556 rail is manufactured by Samson. They also manufacture the Rainier Evolution rail. I have the Samson Evo in 12.37 on my M&P. Pictured here. Great rail, easy to install (just make sure to install the thermal bushing right side up) and locks on tight.

I also was looking at the Samson Evolution rail but nobody had it in stock. 556 Tactical had their model in stock and I actually liked the look of it better. A bit more expensive but whats $10 right? here is my rifle by the way.M&P 15 2.jpg