I am looking at putting together a new carbine upper for my bushmaster. I currently have a flattop bushie upper with a fluted dissipator 16 inch barrel with ak muzzle brake on a colt lower(preban). Stocks are Bushie stubby with extension which works better for me than collapsible , A2, or A1. Sights consist of a trijicon front post, GG&G flip up and AimpointML2 on a ARMS 22m68 mount. This rifle is great shooter but a little muzzle heavy.
Since I have a Colt A2 upper collecting dust I thought I would put a Bushie 14.5 inch M4 barrel with AK74 brake permanently attached on it .  My question is on the handguards and mount for this  setup for my aimpoint.  I was looking at the ARMS 39 but i dont know if they will fit with the M4 handguards.  Other option is Bushies B.M.
A.S. free floating handguards with built in rails and mount the aimpoint to that.  
Whatta you guys think??
I'm a newbie to the site.  I've been a cop for 11 years and Army active and reserve for about 18. I'm a rifle and firearms instructor but I've learned more about AR-15 / m16 reading this sight than anywhere else. Keep up the good work.

Don't limit yourself to just these two choices. There are quite a few gooseneck mounts around; but for the life of me, right now I can't think of who the hell makes 'em. Boy, am I a big help [rolleyes] Anyway, IIRC from reading up on 'em here, the M4 handguards have to have just a LITTLE bit shaved off the top to fit under the ARMS #39 (damned good mount, though). Whatever you decide to buy, I'm going to take the liberty of suggesting you shop with Donnie at [url]http://www.sableco.net/[/url]. Take a look around his website, and e-mail him with any questions you have; he's a good guy (he's also a full-time Sheriff's Deputy), and he'll go out of his way to help you out.