Need a little advice, and thought I'd turn to the experts...I've also posted this in the "Build It Yourself" column.

I'm planning on purchasing an M4 upper (either Colt or Bushmaster) to "replace" the existing upper on my pre-ban Colt. I do have a couple of concerns vis-a-vis getting a flattop model versus the "original."

"Correctness" of the military version compared to my final product aside, which is better suited for mounting of a Trijicon Reflex II sight? Will the existing front sight post/gas block interfere with the field of view of the sight? Or is this just a mounting "thing," and the problem's solved by the height of the mount on the Picatinny rail?

Additionally, any recommendations on brand (Colt vs. Bushmaster) would be appreciated as well.

Thanks in advance

You are correct in assuming that the height of the Reflex mount will solve the problem of the front sight base blocking your view. With things set up correctly the dot will rest just above the front post. As a matter of fact some very accurate shooting can be done when a rear back-up sight is used in conjunction with the Reflex. Looking thru the appreature really focuses the dot for me when trying for accuracy over speed of picking up the target. I don't think it matters which upper manufacturer you choose, but if it was me I'd try to keep things of like make as much as possible.

If you use the RX14 mount, you won't have any sightline issues.  

Thanks, gentlemen - I appreciate your guidance.

You've satisfied my concerns, and I thank you.

Not trying to put you off the Trijicon, but this post might shed some lite on other options available to you.

www.ar15.com/forums/topic.html?id=96611

Mike

I dumped the RX14 mount and put on the ARMS#15 mount with two #15S spacers.  This is a throw lever QD mount and the spacers put the dot over the top of the post.  One spacer puts it right on top of the post.  Very solid.

I have a Reflex on a flat top M4 look a like and like it alot, but if I was to do it all over again with what is out there now I would go with an EOTECH 551 or 552.

I would go with a Bushmaster M4 upper myself. The quality is superb and the price is far below that of a Colt.

DK

Quoted: I would go with a Bushmaster M4 upper myself. The quality is superb and the price is far below that of a Colt. DK

Considering that I built a whole AR for the price that Bushmaster charges for a M4 upper, I would HATE to see what Colt charges... course considering you are using a pre-ban lower perhaps the cost would be worth it.

I am going to wait for 04' before I get my next AR, (hell it will take that long to save up the money) seeing all these guys on the news and in BHD with the M4 has convinced me that I really need to get one  Seeing the SpecOps guys in Afganistan- and more to the point the Settlers and off-duty servicemen in Isreal- just going around with a M4 or CAR dangling at their side like it was a purse.  I'm going "Damn that beats the hell out of a handgun" and since I live in the great state of Arizona with its wonderfully broad definiton of "concealed weapon" and legal open carry in unincorporated areas...