colt sp1 ar15 preban questions

[TRK2AJK]

local dealer has a colt 1r15 preban lower, unidentified upper with colt bolt and bolt carrier.
lower- has sling attatchment points on either side, it is marked ar15. it is in like new condition with a l/new 4 position collapsible stock.
bolt shows little to no wear, i marked with C, carrier is marked with C

The upper is the catch. i t has no markings other than an "so3" or "so2" on the front sight tower. barrel is unmarked as to twist, mfg, anything. also has the 5.5" flash hider. it is in like new condition, it is an A2 upper
i am sure the bottom and bolt are colt, any ideas on the upper.
some one once told me colt did not use the 5.5" flash hider.
any places to check for mfg markings.
thanks, tommy

 

[dfariswheel]

Just below and in front of the rear sight, on the carrying handle, is a reduced area.
There should be a makers mark there, on the right side.

Colt uppers will usually be marked a "C" for Colt, and an "H" for a Colt-Hartford forging, or a "M" for a Colt-Martin Marietta forging.

 

[DMK]

An SP1 carbine should be a lightweight barrel no? Those aren't very common and only made by Colt, Bushmaster (which should be clearly marked B MP 5.56) and Model 1 Sales I believe. If it's chrome lined, it isn't the latter. But then again, if it isn't, it could still be a Colt.

 

[Harry Tuttle]

sounds like someone had a pre 94 lower and did the post 1994 "upgrade" to a CAR

check out this post for what an intact olde SP1 should look like

http://www.thehighroad.org/showthread.php?t=128569