Hi guys. I'm fairly new to the AR platform, so please bear with me here. I just picked up a new M&P15 Sport and, while I love the rifle, there are a few mods I'd like to make. I just need to know what parts I need, and which brands you guys recommend.
I have the newer Sport model, which comes with the MagPul MBUS flip-up rear sight and the A2 front sight. Since there's no way to adjust the rear sight for elevation, I've had to pretty much lower the A2's sight post all the way down to even get close to the bullseye. NOT a fan of the A2 at all.
So, here's what I'd like to do:
Replace the handguard with a quad rail, so I can attach a foregrip and MagPul MBUS front sight. I'd also like to attach a decent red dot too. I would like to get rid of the A2 completely. Here's a link to a UTG quad rail that I've had my eye on: AR-15 CARBINE MODEL QUAD-RAIL HANDGUARD - AR15Outfitters.com
Will this one work for the Sport model? I know a lot of people aren't fans of UTG, but I've used many of their accessories in the past and they've yet to fail me. If anyone knows of a better quad rail around the same price range, please post pics and links.
Now, for the gas block. I understand that the A2 front sight is also the gas block. I'm assuming that I'll have to pick up an aftermarket gas block, but don't know where to start looking.

I only paid $500 for the rifle, so I'm not really looking to spend hundreds of dollars on parts that I could spend on mags and ammo. Any help (pics, links, advice, etc.) would be greatly appreciated guys.

Did you buy this rifle new, or used? Is the front sight post stock? What distance are you shooting at? Which aperture are you using on the rear Magpul sight? Is the front sight base an "F" marked sight?

Before you make any changes to the firearm, you need to get it working in the stock configuration... otherwise, you could spend your money on a cheap quad rail, a new gas block, and a new front sight and have to put the post all the way down to get to the bulls eye.

Another thought as well... can you describe your sight picture? ... just want to make sure you are using the sight properly.

Rifle was bought from a friend who bought it for his wife. Wife didn't like it, so I bought it. The front sight is stock and is "F"-marked. I've tried both apertures on the MagPul at 25 yards. Sight picture is perfect. I even had a friend who's been in LE and military for 15 years try it, only to experience the same inaccuracy.

Oh, and the link to the quad rail in my OP was the wrong rail link. Here's the actual link: UTG PRO Model 4/AR15 Car Length Super Slim Drop-in Handguard- MTU001SS- Primary Arms

Just to make sure, please describe your sight picture, and where you are hitting. Also, where is your eye in relation to the sight? Are you shooting with your eye close to the sight, like nose touching charging handle, or do you have the stock fully extended where you are back away from the sight?

You said you are new to the AR, so we need to determine if this is shooter or equipment issue. No offense to your friend, but I know lots of folks who are former military and LE who don't know how to shoot.

First of all, welcome aboard! Being new is definitely a fun time learning everything and dealing with grumpy crusty *******s like me.

The reason you can't hit the bull is because of the combination of sights you are using and the distance to target. With a rear sight that does not adjust for elevation and cranking the front post to it's limit, at 25 yards your shot placement will be 1" - 1.2" low of the bullseye (assuming you have no issues getting the windage set properly). If you then take that rifle and shoot at 50 yards, you'll be on the bull. At 100 yards you'll hit slightly high of the bull.

IMO, leave the A2-F front sight post and get a rear sight that is adjustable for elevation. Even better for your wallet, leave the magpul polymer rear back up sight on and calibrate the elevation Kentucky windage in your head. In time, getting the right sight hold for an estimated distance will become instinctual. I took a look at that drop in handguards you linked to. Neither of those will support the removal of the A2 front sight post. Both of those use both the delta ring and the handguard end-cap to mount properly. Removing the A2 front sight post means that your handguard endcap has nothing to push against.

If you're looking to remove the A2-F front sight post, what you want to do is install a free-float handguard. Depending on the free float handguard, it will mount to the standard barrel nut or have a proprietary barrel nut. Nothing touches the barrel.



^ That's a 15-Sport... mostly (Lower, small lower parts, buffer tube & spring, upper receiver, barrel, barrel nut and muzzle device are factory.)

I have a set of Troy folding battlesights on it. Windage adjustment on the rear sight. Elevation adjustment on the front sight. When I shoot at 25 yards, I expect to be anywhere between 1" to 1.5" low of the bull. At 50 it's spot on.

The take-away is that dropping on a free float handguard, keeping the magpul MBUS rear sight you have and installing a magpul MBUS front sight will put you right back where you started: rear sight windage only adjustment, front sight elevation only adjustment.



This is my irons only AR-15. With the A2 carry handle rear sight, I can get it to sight on at 25 yards using a combination of the elevation adjustment on the front sight and rear sight. If you want to use one of those drop in quad rails you linked to, you'd need to leave the front A2 sight post and get a rear sight that is elevation adjustable.

__________________
-John

To answer your question regarding how to install a free float handguard. This is the method in a quick nutshell. If you really want to do this, I can go into more detail or point you to more detailed resources.

Brownells - Installing A Free Float Handguard - YouTube

You'll need a few tools. I may miss a few.

1. Vise
2. AR-15 upper vise block
3. AR-15 Bench Block
4. AR-15 Armorer's Tool
5. Beam type torque wrench
6. Flat head pin punch
7. Roll Pin Starter punch
8. Delta Ring Compression Tool (Not essential but makes removing the old handguards easier)
9. Ball Peen Hammer
10. Penetrating oil

Keep in mind that the S&W A2-F front sight gas block assembly uses tapered pins, and they are driven out opposite from every other manufacturer. I can't remember... right to left? Someone here will remember and chime in.

I advise spraying the tapered roll pins with a little penetrating oil. You're going to have to use very stout hammer blows to drive the pin out.

Quick and dirty steps...after removing the stock handguards....

1. Install upper into vise block
2. Install into vise.
3. Use the armorer tool to remove the flash suppressor.
4. Be sure to save the crush washer.
5. Remove upper from vise.
6. Put front sight gas block into bench block.
7. Hammer out tapered pins.
8. Slide off FSB/Gas block off barrel. Set aside. Make sure not to bend or kink the gas tube.
9. Put upper back into vise block, back into vise.
10. Remove the barrel nut using the AR-15 armorer's tool.
11. Remove the Delta Ring
12. Remove barrel.
13. Go back to the FSB/Gasblock.
14. Tap out the small roll pin that affixes the gas tube to the FSB/Gas Block.
15. Remove Gas Tube and set aside.

Once you got it all apart, check the instructions that comes with whatever free float system you choose. Some free float handguards use proprietary barrel nuts. Some utilize the stock barrel nut.

When reinstalling the barrel. Set the torque wrench to 35 lbs. Torque until the wrench reads 35 ft/lbs, loosen, torque to 35, loosen, torque to 35. You'll then have to time the barrel nut so that the gas tube can pass through. Do not exceed 80 ft/lbs.

YHM makes a clamp style low profile gas block. I have one installed on my 15-Sport.

__________________
-John

I must also put out this caveat. I am in no way an AR-15 armorer, M4-gery expert, gunsmith, long gun distance marksman, or anything of the sort. I'm just an average old firearms enthusiast. If anything I put out there is wrong, the other guys will correct me and I will be gratefully humbled.

That's all I got. It's been a long day at work non-stop troubleshooting computer issues. My brain is fried.

__________________
-John

I understand that the UTG Pro handguard won't get rid of the A2 front sight. I had considered installing said handguard and replacing the A2 with a flush railed gas block, maybe a Rousch, like this one: Amazon.com : Rousch® Regular Profile Flush Mount Picatinny Rail Height Block +Stainless Steel Roll Pin .750" Model 15/4 .223 5.56 7.62X39 300 AAC Blackout .22 etc.. : Sports & Outdoors@@AMEPARAM@@http://ecx.images-amazon.com/images/I/41yNF%2BKxn9L.@@AMEPARAM@@41yNF%2BKxn9L.
Accuracy aside, I simply can't stand the A2 front sight. It bumps into and gets caught on everything, so it has to go. Also, I was under the assumption that I was limited to 'carbine-length' handguards. But, from the pic of JaPes' M&P Sport, I'm beginning to think that I am wrong.

JaPes, I do love what you've done with your M&P Sport. What brand/model/length of FF handguard is that in the pic?

Even with out elevation adjustment on the rear, he should be able to get on at 25 yds... but it might take your front sight to the lowest setting.

Like JaPes said, take it out to 50 yards. Get it on at 50 and you will be within 2 inches +/- out to 200 yards or so.

JaPes has a Troy Alpha on his rifle. They are available in various lengths. If you free float the barrel, you are not limited to carbine length only hand guards.

As far as bumping and getting the A2 front sight hung on something... replacing it isn't going to change that for you... that is muzzle control. Instead of hitting the A2 sight on something, you will just hit the new sight, or the barrel on something instead.

^ What he said.

I installed a Troy Alpha rail. It's considered old tech now. The newest generation are the slimmer, lighter keymod handguard systems. Midwest Industries makes some nice and relatively affordable stuff.

Midwest Industries: Lightweight KeyMod Series One Piece Free Float Handguard

The Troy rail was good for it's time. It's a PITA to affix rail sections to the holes in the handguard. I could only affix rails as far as my fingers could reach. I almost needed four hands to get the job done. It took me a while and a bit of swearing to get it done.

If I were to install a free float handguard now, it would be a keymod type.

ALSO... A BIG ALSO... don't go buying random parts of Amazon. Even some of the "sold by amazon" can be counterfeit parts or just utter garbage. If you want a good gas block, check out YHM.

Gas Blocks - Firearms Accessories | Yankee Hill Machine

__________________
-John

One more tip. Accessories, especially MagPul branded items, have very convincing counterfeits on auction sites, Amazon, etc. They're nearly impossible to discern when buying off places like this on the internet.

Don't let a brand name + a too good to be this low price fool you.

I've given up buying Magpul items on the net. The only way I know I'll get the real deal is by going to the store and examining it before buying it.

__________________
-John

Oh, don't worry. I'd never buy anything except (maybe) a foregrip from Amazon or eBay. I'd only buy serious parts straight from the manufacturer or something like Cheaper Than Dirt. I just needed to use that link as an example of the type of gas block I was talking about.

However, I am looking for a gas block that fits a .750" bore diameter, correct?

I'm looking for the same thing. How about this one?

Yankee Hill Machine Gas Block Flip-Up Hooded Front Sight & Bayonet Lug

This is fine if you're sticking with a carbine length hand guard, but if you're adding a free float hand guard longer than 9", you will need the low profile gas block and a rail mounted folding or fixed front sight.

__________________
SFC, US Army, Retired

tried the link in bold no sucess
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I put a Midwest Industries free floating quad rail on this PSA upper assembly with a Spike's lower- I know this isn't a S&W M&P-15 Sport or Sport II, but the exercise is the same.

The hardest part was removing the A2 sight/gas base- if you think knocking the pins out to slid off the sight is easy, it's not unless you have the proper jig. I used a 2 x4 block and it was slow going, but I got those pins out.

Here's the link to my thread on making the swap:
Error | Northwest Firearms - Oregon, Washington, and Idaho Gun Owners

Geno