I:E BUSHMASTER,ROCKRIVER ARMS,COLT,??????     WHO MAKES THE BEST PREBAN FLAT TOP UPPERS.

If you are talking about uppers only, as in stripped uppers, I would say their isnt a great amount of difference in them at all. But they all do have small differences that may or may not matter much to you.

Bushmaster does use a grey dry lube finish on the inside of all their uppers, which is a really nice touch.

Rock River used to have a problem with out of spec flat tops, but Im supremely confident that is taken care of now.

New Colt upper will have the extended feed ramps cut into them to correspond with the M4 feed ramps on Colt barrels (and only Colt barrels).

If you are talking complete uppers... again, they are all somewhat close, but contain small differences;

Complete Bushmaster uppers will have the dry lube coat on the inside as noted, will have 1/9 twist chrome lined barrels made with 4150 milspec steel.

Complete Colts will have the M4 feedramp cuts with a chrome lined chamber (and bore of you get it with a M4 or A2 barrel). Barrels will be 4150 sttel and will probably be 1/7 twist.

Complete Rock River's will have your choice of 5.56 chrome lined or .223 Wylde non-chrome lined barrel. But both will be made with non-spec 4140 steel.

Colt will be much more expensive than Bushmaster of Rock River. Bushmaster will be a little more expensive than Rock River.

Damn new-arguy, you are on the ball. 5x5.

No, just really bored with nothing much else to do today other than cruise the site...

Here is a tidbit on the Bushmaster dry film lube.  


FROM BUSHMASTER:
The finish on the inside of the receivers is a dry film lubrite coating that is sprayed and then baked on. It is very similar to the finish on the G.I. magazines. It does not last like the hard coat anodized finish and is intended to help with the break-in of the rifle. Some solvents can remove it. We use the same coating now on our receiver extension tubes.



I intend to use Perma Slik to do the inside of my Colt M4 upper before I have the upper built.  Then I get both the extended feed ramps and the feed ramp cuts.  You could also pay to have the feed ramps done on a Bushmaster after assembly by a gunsmith... but I wanted 1x7 twist.  I figure the parts of the finish that remain will help prevent corrosion in the upper reciever and the cost to do it will be negligable.