i noticed at the gunshow alot of the upper receivers had the same marking as my S&Wx, does smith outsource their uppers or was i switched? i will post pictures asap camera is being difficult at the moment.

well the keyhole mark i was talking about is a cerro forging mark, either they are making them for smith or smith is using there forms, not sure but this is what i have found out so far.

According to Patrick Sweeny in GunDigest, early S&W ARs were assembled by S&W mainly with parts from CMT.

Initial serial numbers were three digit. Mine is four digit, SN 25XX.

Serial number prefixes (SN, SW, SM) may or may not have relevence to how early a production date. Anyone know for sure?

i have 5 digits sn 19xxx, sounds like urs must be a real early build not sure, does urs start with sn,sw,or sm

SN is the prefix. Sweeny states that he saw four digit serial numbers and the serial numbers were "roll marked" in contrast to the early three digit number (223) he tested. In a picture of that model, 5.56 is clearly marked on the lower. Mine only has 5.56 on the bbl. He said that S&W might eventually make their own parts but the early ones were assembled by them and fine tuned for their quality standards. Parts were probably selected from bins by S&W QC folks and assembled at S&W so quality was (at least in that timeframe) kept very high. CMT is/was the supplier for parts to many manufacturers with varying QC standards so just the parts maker tells little other than capability to produce high quality.

im thinking that the ones marked sn with 5 digits are the newest builds, cableas got a shipment of some in aug starting with sn and around the 15xxx numbers

I just returned from a large chain bookstore where I bouht a Valentines card for my wife. they had a "S&W catalogue" for sale that I looked through and (book dated 2006) states that the M&P15 serial numbers begin with SW. Possibly the first batch of lowers were produced by an outside supplier and identified with the SW prefix. I know folks with M&Ps a few years old that have SN like mine with higher numbers than my (new in Dec 2010) example. I am pretty sure mine is new "old stock" and my ex LEO friend FFL dealer told me that Bud's , where I bought mine from, often buys large batches of weapons from other distributors or dealers who have financial problems. He could not buy the 15 OR from his supplier for what I paid including shipping from Bud's. He was good enough to transfer for me for 25 dollars, five of which went to FDLE for the background check.

I think if the equipment is correct on yours you should just relax and enjoy shooting it. The only ones I would not want to speculate on , quality wise, are the new low priced and down graded versions which some even state have some advantages (twist rate, questionable to me) vs. downgrades (lack of chroming on bbl. and cheaper components in some cases).

Mine is SW i got it in 2008