I'm thinking about getting a new AR this spring. I have narrowed it down to
either the S&W M&P 15 sport and the Ruger AR 556. They both go for around
600 bucks.
What will you be using the AR for? If it's just for plinking I don't see a big enough difference between the two to say one or the other. I think they'd both do just fine for that and it just comes down to which one feels better to you.
I would go for the Ruger only for the following reasons. It was my understanding that the M&P Sport didnt have the forward assist or dust cover. However, many will say they are not needed.
Is the ruger the gas piston? I thought the ruger 556 was? But I also thought is was closer to $1200? Maybe I'm thinking of a different model... If it is the piston model I would definitely go with the ruger.
All other things being equal, I'd probably just get the one closest to the fit and finish you like.
My M&P sport has a 1:8 twist and I love it. No forward assist or dust cover, but I'm not patrolling Baghdad with it. I was able to squeak out sub-moa at 100yds, and that was my first time ever shooting at that distance. I think it was 69gr hornaday match. Yeah twist makes a difference. A 1:9 would probably be better for the lighter varmint rounds, but realistically I'd doubt you'd notice a difference between the two. They both will adequately stabilize the majority of the "box" ammo you can get. I'd stay away from the heavier stuff (69and up) if you go with a 1:9. Yes I'm sure there are lots of people that shoot heavy/long rounds through a 1:9 all day. But the majority of the ammo designed for 'yotes is in the 45-55gr range, or even lighter.
I'd go with the ruger hands down. That's my .02...
Why don't you build an AR? You can easily build one for $500ish. I bought my first AR complete. I built my 2nd and I will never buy a complete rifle again. It's more fun to build it!
I have no experience with the new Ruger AR, but I have an M&P 15 Sport that was gifted to me, and I must say I dig it! Integral winter trigger guard is a plus. Factory trigger is pretty darn good, for a $600 rifle!
I am a bit of a Ruger fan, so I hope the AR556 stacks up to the M&P! As was said, I doubt you can go wrong with either!