Hello,
I would appreciate your input Guys since I'm new in the rifle world.
I own a couple of long rifles I picked up this year. Other than add ons like scope, grips, bipod I have done nothing else to them. I haven't or ever have changed the handguards on them. I wanted to leave those as is with the stock handguard.
I just purchased another one though, this one I plan on doing more work on, definitely changing the handguard for a rail.

Can you tell me what is the longest rail I can put on my stock SW AR15 Sport 2 without any barrel mods?

I've seen some long ones but I think they are extending the barrels which is not something I want to do right now.

I would like it to come just short before the beginning of the bird cage muzzle brake.

Your responses would be helpful, Thanks!

Not sure what you mean by extending the barrel. Barrels can be replaced but not extended, no need to do this for fitting a longer handguard. Your barrel is 16" long so generally you don't want a handgaurd longer than 15". Personally I like 12" hand guards on a 16" barrel but it's personal preference. The standard handguard is carbine length (6.75-7").

There are a couple of different types of handguard, snap-in that use the existing barrel nut + delta ring and the FSB handguard cap, these are the easiest to fit as no tools are required you just pull the delta ring back and snap-off the old handguard and snap in the new one (they are two parts). However they contact the barrel which can have an impact on accuracy, although in an AR it's debatable how noticeable it is.

The second type of handguard is free-float, fitting one of these generally requires removal of the standard barrel nut, delta ring, and FSB and replacing them with a handguard specific barrel nut and a low profile gas-block. This is not that hard but does require tools and a bit of mechanical common sense, doing it wrong will cause your rifle not to function so if you're not comfortable go to a gunsmith. There are a couple of options (Troy) that use the original barrel nut so you don't have to remove it but you still have to remove the FSB and fit a low profile gas-block. Advantages are the handguard doesn't touch the barrel except at the barrel nut so in theory the rifle should gain some accuracy, you can also put an iron sight much further forward on the barrel to give yourself a longer sight radius and you can fit any length handguard you want without worrying about the front sight base.

If you want a long handguard you can fit yourself and aren't worried about the free-float advantages, there are some semi-snap in handguard options that have a cut out for the FSB that you might consider.

GAS BLOCK CUTOUTS: Samson Manufacturing (I have no experience of this handguard).

My preference is to go with the free float barrel, my favorite being the Geissele SMR 12".

Great, great advice. I'm a fan of free floats too, but like them a little longer. Love a 15" rail on a 16" barrel.

There are a few longer drop in rails that require no modifications to the front sight/gas block, but they are few and far between. @arnoob gave you some products to look at, I did notice thought that they are expensive!

Here is another cheaper option, but it won't be as quality as the others. Still, it would accopmlish what you want. Qualifier, I have never bought any of these products so I have no experience with them.

Leapers UTG PRO 15" SuperSlim Drop-In Handguard - MTU015SS - 4717385550278

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Still carrying my S&W 642

I have been looking for this through google searchers for 6 hours... THANK YOU!

Are there gas blocks you would recommend? I'm hoping not to break the bank but don't want to have a rifle that doesn't function.

If you would be willing to help me out, I would appreciate if you could help me understand this product: Leapers UTG PRO Model 4/15 Rifle Length, Super Slim Free Float Handguard, 15" - MTU019SS - 4712274526211

It specifically says it works with a standard gas system. Does that mean I can keep the gas block as is?

Sorry for entry level questions, I'm still quite new!

No worries.

No, that's a free float rail that needs a low profile gas block. The A2 front sight on your Sport has the gas block built into it, but that's not what they are referencing when they say standard gas system.

Do yourself a favor, do a lookup on YouTube on freefloat rails and removing the A2 front sight post and watch them. It will help tremendously and you'll better understand the gas system and how it works and what parts it needs to operate. You need to understand how your rifle works with its current parts first before looking at parts to swap out. You got lots of fun ahead of you.

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Still carrying my S&W 642

Thank you! My biggest frustration has been that the YouTube videos tend to assume a certain starting point that I just haven't reached yet. I watched three or four videos that literally said "and then you put in the gas block" and one video that the guy was drilling into the barrel without mentioning it was a custom build instead of a refit.

Either way, I'm getting there and it's been a ton of fun learning! Thank you for your help!

I've installed a free-floating 1-piece quad rail on an A2-equipped barrel before- you need the proper tools, patience, and the ability to use them without damaging the finish on the barrel. If you're a beginner and you just want the free float, quad rail look w/ no A2 sight, you're probably better off getting a M&P-15T- quad rail factory installed by S & W. Factor in the cost of a quality quad rail and gas block as well.

Yes, this model is a bit more than the Sport II version, but has the Magpul MBUS sights, as well as the Armonite-coated 16" barrel with 1:8 twist and the free floating quad rail. If you are planning to mount a scope on your rifle, flip down sights are preferable to the A2 sight blocking your line of sight- the M&P-15T offers an optics -ready platform out of the box.

Geno

These are great insights! I actually do not have a sport, but this was the only thread I found with the info I needed. As far as I can tell it's a standard M&P-15 (811000).

TMI: A little under a year ago I needed to purchase a new handgun while my shield was in for 3 months of repairs and found a BEAUTIFUL used M&P-15. Bought the 9c and 15 for around $1,000 combined (with spare optic and spare mag for the 15) and have been gradually upgrading since then.

The M&P-15 is a great basic rifle- if you found it for a good price, it's worth upgrading as you see fit- put a better handguard on it, swap out the A2 sight/gas block with a low profile gas block, add flip-up sights, better stock and grip on it. The furniture upgrades do add up, but then you end up with a rifle you really like and is comfortable to shoot.

I've built 2 AR-15's from parts and assembled uppers- at this point I'd rather buy whole ready -to shoot rifles and just make tweaks on them, like replace stocks, add rail covers and maybe a bi-pod or flashlight. Most guys start with a M&P-15 Sport or Sport II, add a keymod or quad rail, but then again you're getting into the gunsmithing to make it happen.

Geno

If you are sure you will add a front sight to the rail on your handguard or use a scope or dot sight, get out your hacksaw and cut off the top of the front sight. Instant low profile gas block. I did one years ago and didn't even remove it from the barrel. Hacksaw cut got smoothed over w/ a flat file and colored w/ a marker. Doesn't need to be perfect as it will be hidden inside the hand guard.

Use the hacksaw for the sling loop too

Good advice, the only issue is making sure the handguard you buy will fit over the cut down A2, there are some slim handguards that won't fit over it or only fit over it if you really shave down the A2 a lot.

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Still carrying my S&W 642

Does anyone know if the UTG, referenced above, will fit the M&P optics ready model?