603 (M16A1) and A2 front sights?

Discussion in 'AR-15 Discussion' started by sputnik1988, Jul 5, 2013.

  1. sputnik1988

    sputnik1988 Active Member

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    I'm really into the idea of putting together a retro build and am looking for a bit of advice.

    My first question was, is there any difference between a Colt 603/M16A1 front sight and the standard A2 sight, either functionally or cosmetically?

    My second question is if no difference, would I be better off to find a barrel with the A2 front sight already attached? I want to go as close to correct as possible without too much headache. I realize that AR parts are a bit difficult to come by right now but I can't even find a listing for a pencil 20" barrel with the sight attached. Anybody have any tips, thoughts or suggestions?
     
  2. darthjkf

    darthjkf New Member

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    A1 only has side to side adjustment for sights and A2 has not side to side and up and down.
     

  3. sputnik1988

    sputnik1988 Active Member

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    The front?

    Is there any difference in the dimensions?
     
  4. JonM

    JonM Moderator

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    no. the barrel profile and handguards are the only diff between A1 and A2 barrel assemblies. the A1 can have one of three different flash hiders as well. the A2 only has the half birdcage (best all purpose flash hider for the AR15)

    there currently arent any true 20" pencil barrels being made to my knowledge other than the occasional green mountain http://www.gmriflebarrel.com/milita...barrels/m16-a1--556mm-20--112-twist-20-barrel even that one is sporting M4 cuts. you could try the folks at krieger or white oak.
     
  5. kbd512

    kbd512 Well-Known Member Lifetime Supporter

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    Apart from forging marks (markings varied over time and according to the supplier of the forging), machining the flash from the forging (only done on A1 FSB's), and a different diameter hole for a different diameter barrel (.625" vs .75"), I can't recall any other major differences between A1 and A2 FSB's. There may be some minor geometry differences that I can't recall.

    Functionally, there is no difference between the M16A1 and M16A2 front sight blocks. Both have a sight tower that accepts the same pin, both have a bayonet lug on the front, and both have a sling swivel mount on the rear.
     
  6. sputnik1988

    sputnik1988 Active Member

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  7. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

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    The A-1 sight is a 5 position tapered post. The A-2 sight is a 4 position straight, squared post
     
  8. kbd512

    kbd512 Well-Known Member Lifetime Supporter

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    Forgot about that. The last M16A1 I used was in boot camp.
     
  9. sputnik1988

    sputnik1988 Active Member

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    One more question, If I end up going with an A2 sight, should it be a standard or F marked FSB?
     
  10. kbd512

    kbd512 Well-Known Member Lifetime Supporter

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    The "F" marked sight bases are slightly higher than A2 FSB's and were intended for use with rear sights mounted to a picatinny rail upper receiver.

    Since early M16's, at least those used prior to the 1980's, didn't have picatinny rails on them, there's no need for a "F" marked FSB.