Shot my co-workers M&P 15T several times, it's traditional AR, through and through. Very light, easy to add accessories. The price when they first came out was around $900.00

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Just like my Sig556, which was around $1200 in Feb 08. Now they are both more. I just wanted something "other" than a traditional AR, and now want an exact duplicate of deepwaters FAL in .308.
However, Sportsman Guide is selling complete Colt M16A1 packages (everything but the lower receiver, and trigger disconnect), for $599.97.
I know your a S&W fan, (so am I), and it is a fine rifle. The Ruger I have seen, held, fondled, but never shot one. So I cannot speak to actual range comparisons.
For the money, the M&P is a great choice. So is getting a complete kit upper from Colt, and throwing it on a DPMS lower, for less money.
Is this going to be a comp. rifle? Or just something to have back in NM? I like the additional weight up front my Sig, and the SR has it stabilizes the weapon (for me), when rapid firing. Especially, when I get the moderators approved Titan Compensator.

(Eric uses his Sig556 as his primary BTW)

Just another .02 cents, for ya'. The Stag is about the same and, as others posted, the same in the M&P category, BUT cheaper.
Please let us know what you decide on.
Take Care.
tw