Want to throw a 13 inch Troy Alpha (or similar) on my M&P1 15 Sport 2. I realize that means removing the A2 sight and installing a low-pro gas block. This is my first AR and although I'm handy (work on dirt bikes, etc.) this is a firearm and I've never worked on one before. Is this a reasonably simple job? Does it require any special tools? Is it a fortune to have a gunsmith do it? I live I SoCal and would have to seek out a gunsmith.

Thanks.

You would need a hydraulic press to remove the front sight pins. A local shop has done these I my area for about $60 plus the gas block. Just keep in mind removing the front sight voids the warranty .

Youtube. Get R Done.

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Here, a grain of salt.

Not knowing the exact configuration that you ultimately want, it sounds like you are talking a modification that would fall under NFA.

It is relatively easy, and affordable, to assemble a separate upper. Tools are relatively inexpensive, as would the required parts.

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Judge control not gun control!

I think OP is talking about a 13" Troy Alpha free float rail, not a 13" barrel, so no worries on NFA rules.

OP I fitted a Geissele SMR to my M&P which is basically the same job and didn't have too much trouble, I'm not a gunsmith or a mechanic, I'm just reasonably handy and have some common sense and that's pretty much all you need to get this job done. You don't need a press but removing the taper pins from the FSB is the most frustrating part of the job for sure, just make sure you have a decent ball peen hammer some nail-set punches and a way of solidly supporting the FSB / barrel (I got some hardwood 2x4 and cut a custom jig in the face of it to save some cash, but you can buy a proper jig at Brownells, just gotta stop it bouncing when you beat on it). Remember they are taper pins so you have to beat them out the correct direction, which on the M&P Sport is the opposite of most rifles - they come out right to left.

Honestly if you don't plan on going back to stock ever I would consider just taking a dremmel and cutting the top off the factory sight post, saves you the hassle of removing the taper pins, means you don't have to worry about alignment and those pinned FSBs are solid as a rock, and saves you $$ on a lo-pro gas block. It's the way to go if you never want to go back.

The only special tools you will need is an AR armorers wrench for the barrel nut, I used a $20 one from Amazon it worked fine, if you plan to do a few more ARs though it's probably worth spending the extra on the Magpul one ($80).


Oh yeah, all of the above will void your warranty blah blah really who cares on a Sport

arnoob thank you very much. You are correct I won't go back so dremelling is the way to go. Great idea!

Unless your new rail uses the existing barrel nut and delta ring, you will still need to remove the FSB to remove the gas tube and barrel nut assembly so that you can install the proprietary nut for the rail. The taper pins should be able to be driven out.

The Troy Alpha says that it "works with standard AR15/M16 barrel nut so I think I'm ok?

...but it is silent on the topic of delta ring...?

I guess you could cut the delta ring and spring off, be careful that you don't damage the barrel nut or gas tube.

I've never needed anything other than a punch and hammer to drive the taper pins out and back in. Try that first. AR15.com has some good tutorials on AR projects.

I'd just cut the delta ring off when cutting down the FSB. The taper pins aren't impossible to remove, but they are pressed in on the M&P so it can be something of a pain, you won't know until you beat on them a few times. One of mine came out no problem at all, the other required a lot of beating and some heat as a little additional persuasion.

Wrong. S&W front sight post/gas block pins are driven in/out opposite of nearly every other rifle. Penetrating oil, a sturdy pin punch, and stout hammer blows are required.

Instead of cutting off a delta ring or cutting down the FSB, why not just buy the required tools to do the job right? Vise block, armorer's wrench, pin punches, penetrating oil, thread anti-seize, a new crush washer for the muzzle device, YHM low pro gas block.

Having the correct tools makes the job easier than hacking away with a cutting wheel on a rotary tool.

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-John

I would search YOU TUBE to see if you can find video. That will help you decide if you can DIY.

If you have any mechanical aptitude, the ability to work in sequential order, the ability to comprehend an exploded parts diagram, acquire the correct tools, then you are most likely capable of doing the job on your own.

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-John

Yes he could do all of that, and I did for mine, but there's nothing wrong with cutting down the FSB, it's better if you can pin the gas block and the holes for the factory FSB are already drilled through the barrel.

You have already learned the most important lesson of gunsmithing:

KNOW WHEN TO STOP/QUIT!

Long ago this was explained to me by an old (93 years) gunsmith.
Knowing you limits is very important.
You have learned to question you abilities and are on the way to learning more about gunsmithing.