Rifles and parts to build rifles are very limited right now, if you wait a bit, that will improve.. however there are rifles and parts available, but they are at a premium, and if you go to "Gunbroker", you will be competing with every other so and so that thinks he must have the rifle you are bidding on..

Armlist is also a good source to buy from individual's but they have recently gone to a pay to join format, and it run's about 6 bucks a month..

Smith and Wesson, Rock River, and Armalite, build their rifles with proprietary parts, which will not interchange with other brands. In fact parts for the 308 AR can be divided into 3 major groups with variations on these 3 platforms.

AR-10 is Armalite, only Armalite builds an "AR-10".

DPMS Pattern Rifles, the DPMS pattern rifles come in either a "High or Low pattern" rifle, the most common is the High pattern rifle, so handguards must match the receiver as either High or Low pattern.

The Smith and Wesson MP-10 is a DPMS platform rifle, it is a very good rifle and has few problems, but several posters in the past have reported serious issues with their particular rifles.

I suggest you read the M&P 10 thread here on Smith and Wesson Forum, it is dedicated solely to the M&P 10, although other members have been very helpful to me, although I ended up with a different brand 308 AR..

I would also suggest you join 308 AR Forum, they are very knowledgeable and very helpful, a little colorful, but very nice generous guys that love the 308 AR...

I ended up with a particular brand because I wanted a billet receiver and no forward assist, I've been very happy with my rifle and it weighs around 7.5 lbs without mounts and scope..

Some 308 AR's are very heavy, especially with a longer barrel, I went with an 18" barrel and a carbine stock, its very handy, but it is solid, and as I said, weight and balance are very important.

If you are having difficulty, I would suggest calling Smith and Wesson and enquiring as to availability, and which stocking dealers might actually have them in stock and ship it to your FFL.

Feel free to PM me with any questions, I'm also Billy Magg on 308ARforum and Texas Hunting Forum which I joined because I built a 300 HAM'R on a small frame...

One final thought, Armalite was the original AR-10, it would use the M-14 mag with a few mods, the B pattern is completely different, and uses newer style mags..

Most DPMS rifles will run with P-Mags, Lancer Mags, and SR-25 pattern Mags... and if you intend to modify your rifle down the road, you will need to make sure that the rifle you buy will take those mods:

There is NO 308 AR milspec, as their is with the AR-15, do your research! sorry for the book, but I don't want someone who want's a 308 AR platform rifle to have to learn the hard way..

I am very happy with my rifle, and I really enjoy shooting it much more than the 5.56/.223 simply because I can actually see what I'm hitting on my range.

I did also build a small frame 300 HAM'R as it is so much handier to carry around the farm.. and in .30 cal...