Hey guys im getting my first AR soon and im looking at the M&P 15 sport. Ive heard a few good and bad things but mostly good. What I plan on doing is getting this as a base and getting a Daniel Defense upper receiver and then upgrading the stock barrel and so on. My main question is this. Is the stock barrel and gas tube and and stuff compatible with aftermarket uppers? Im sorry if my info is not good this is my first one and im not 100% sure of all the parts.
Thank you

Why not just save up and buy a complete Daniel Defense rifle

because the sport is 500, the DD upper is 120 and a barrel is 200ish and the DD is 1,400

i don't think the sport is the way to go if you plan on swapping parts right from the get go. I got one but only because i didn't want to spend a lot on a complete. But to answer your question i think you'd be ok

Are you trying to have this eventually become the same as the DD rifle?

im not sure maybe, i just want to kind of build one myself and this seems like the easiest way if that makes sense

Yes, it'll work fine.  My secondary gun is an M&P15 Sport lower, DD upper, MaTech BUIS, DD BCG, DD CH, DD EZ CAR Rails with the M&P15 Sport barrel.  It's been a great weapon, currently 1700rds through it w/no failures.  I really like the Sport's lower and Melonited 5R barrel.  I used all of the M&P15 Sport upper components with another barrel and a Cav Arms CAV-15 MkII lower for a build for my daughter, which has also turned out great.

Then just build one.  Don't buy a complete rifle to use it as a build.  If you don't want to build from "scratch" then buy a complete lower like one from Palmetto State Armory.  Then, buy a complete upper.  

PSA complete lower...$239.00
PSA complete upper...$399.95
FFL and shipping cost...$70 (plus or minus a few dollars)

Total...$710 for a higher quality rifle than the S&W M&P Sport per the specs.  (I don't mean to start a "this rifle is better than that" battle)

as you can see im new to this and do not know what is good and what is not ..are these parts as good as Daniel defense and S&W?

+1

I picked up the Sport when it first came out for $500.  There weren't all of these smoking hot deals from PSA and prices were much higher across the board.  I figured what I used from the Sport for my build to be modestly at $300 for the complete lower and the barrel assembly, as M&P15 complete lowers were going for $300-350 at the time.  With the other components I bought, that put me at $750 for a complete rifle that was better than any of the mid level offerings and just shy of the higher end stuff.  At the time it was about the best you could do for $750, but now you can build a PSA with a better barrel for less, or get a complete Spike's for about $750.  Unless you already have the Sport, I'd have to say that a PSA build is pretty much unbeatable on the low dollar side right now.  (I've built 2 myself )

ok will do ...no i do not have the sport yet im trying to do all this reserch before i spent a bunch of money

Dude (if I may call you that ), I think your plan is fine.  I got a Sport a few months back and I'm quite happy with it.  I bought it with the intention of swapping upper receivers from the beginning.  I swapped to a BCM M4 upper receiver, it was a near-perfect match finish- and fit-wise, and I recommend you consider it.  I've also made a few other mods to it.  I'm using the original non-FA, non-E-port-cover upper for a dedicated .22 upper.  

I have several Colts, so this is a beater, knock-around, training rifle for me.  Nevertheless, I'm impressed by the value of this rifle.
So far, it works the way it's supposed to and I have no complaints.

You mentioned "upgrading" the barrel.  You might want to think about that.  The barrel in this rifle has a lot of features that other folks upgrade to.  It has a 5.56 chamber, F-marked front sight base, M4 extension, 1-8 twist, 5R rifling, medium contour, and is melonited.  What's not to like?

Buy it, change the upper receiver if and when you want to,  put decent furniture and sights on it, and shoot the hell out of it.

JMHO.

ETA:  I spent $540 for my Sport (on sale at Cabelas) and less than $100 for the BCM receiver.  I have no doubt I could have recouped a major part of the receiver cost by selling the original Sport receiver on the EE.  Considerably less than most quality parts guns you'll put together, and I have a factory warranty.

You can read a little more about mine in this thread: http://www.ar15.com/forums/t_3_12/540969_Smith_and_Wesson_MandP_15_Sport____add_pics_of_yours_.html

I haven't used a PSA lower, but they should be fine.  (I will say that i really like the M&P15 lower with the integral trigger guard.)  As far as the PSA uppers, the standard ones I like a little better than the S&W, just because the BCG is a FA BCG, otherwise I'd say they are about the same as the S&W uppers.  Now if you get a PSA upper with a CHF barrel, then you approaching the quality of DD.  Like I said, as much as I like what I was able to build from the Sport, if I had it to do again right now I'd go with a complete PSA build with a CHF barrel.

ETA:  If you still want to go with the Sport as the basis for a build, it's not a bad option, just not the most economical.  You can see what a "DDS&W" looks like here.

You can get almost any DD as a complete rifle new under 1200.

well im going off the msrp prices, also i dont really have a shop around here that sells ARs so I dont know how much things really cost or where to buy them from

I suppose if you wanted to buy the M&P15 Sport and a DD upper I see nothing wrong with that.  That way you would have two separate uppers to shoot with from the same receiver.  I wouldn't want the same two uppers though.  Maybe a 16" and a 20" for example.  On the other hand, if your whole purpose is to buy the DD upper and just shoot that one exclusively, then buying an entire M&P15 Sport to use as your base lower receiver seems like a waste of money.  That is unless you did what I first mentioned.  As somebody else pointed out you can buy a complete lower receiver for a lot less than an entire rifle, no matter how good a deal it is.  I've seen complete lower receivers sell for $200-250 depending on make.  Then all you'd need is your DD upper and you're good to go.  Personally I like the M&P15 and have recommended them a few times to folks on this forum.  They're well built and a great value.  Before you go buying another upper, you might want to go shooting with it to see what you think of it first.  I've seen them sell for $580 at gun stores in my area.

Order the DD upper that you want & build the lower of your choice.

I bought mine and replaced the upper with one from Rainier have shot about 1,000rds with out a problem. I'm building an SBR with another S&W lower and will use the BCG and barrel (will send to be cut to 10.5) from the sport. Great rifle for the money, my .02.