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Posted: 3/6/2005 7:10:33 PM EDT
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Will an original Colt M16A1 (light barrel) sights align properly with an A2 upper receiver (Bushy) Thanks All!! |
They should be, but you never know, especially with Colt. They are the masters of odd configurations. The changes in FSB height came along with the flat top upper receivers and their carry handles - the infamous "F" stamped FSBs. 
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According to my measurement YMMV. From center bore of bbl. to machined flat on sight base where the frt. sight scews in. The pencil bbl is .0325 shorter than gov profile.(all Colt) This is how I measured it right or wrong. O.D of pencil bbl between legs of sight where pinned to bbl. .625 divided by 2 for bore center, then added measured height from same bbl. surface to the flat surface where sight is installed on sight base. Did the same on the A2 gov profile .750 divided by 2 for bore center and added measured height of base. Subtracted the pencil bbl total from A2 gov profile bbl. total for If there is any other better way to do it I can try. other than pounding out the pins and removing sights. Hope this helps. |
| Thanks for the help! As you have probable guessed by now, I am building a pencil bbl configuration with an A2 upper hoping to make it fairly light weight overall. I do realize that there or other ways to lighten but these are the parts I have on hand so I thought "why not put them to use"? Guess I'll have the final answer when I try to zero it!! Now I found an extra A3 upper in the parts pile... hummmm?? |
| I popped a laser bore sighter (chamber type) in it and it looks pretty close. Again, once I get to the range I'll know. I do apprreciate your measurments. This Colt A1 light used to shoot about 1 MOA with ball M193 if I remember correctly. One of the few that ever shot that tight for me! |
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