Front flip sight on a gas block ?

Discussion in 'AR-15 Discussion' started by ktmboyz, Jul 14, 2009.

  1. ktmboyz

    ktmboyz New Member

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    Sorry for another dumb question but I'm not sure and this is my only reliable place to turn.
    I have a S&W M&P 15 optics ready which has no iron sights just a pic rail on the flat top and the front gas block. I purchased front and rear flip sight and a rear carry handle. I can't get the sights even close to dialed in :mad:
    My question is are there different flip sights for a gas block mounted vs a front rail mounted ( height difference) A guy at a local show was telling me they were different. I got my sights from the dealer where I purchased my ar thinking he would know what to sell me.
     
  2. dog2000tj

    dog2000tj New Member

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    I do believe the front flip up sights are different for a gas block vs a rail mount. Check the manufacturer's site for the sights you have, see if they offer 2 different front sights.

    When you say "not even close", how far off are you? What distance are you working with? I would suggest starting at 25yds at first.
     

  3. ktmboyz

    ktmboyz New Member

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    I have checked the S&W site and doesnt say anything, it doesnt even list them for sale. I called them a couple months ago and inquired about the oem ones but they were like $200 each so I went with utg sights from the gun shop where I purchased it.

    When trying to sight it in I had to get to prob 10 yds to get them on the target. I would say prob 12" low at 10yd. I have the front screwed amost all the way down and even if I bring the rear all the way up it doesnt even come close still, which is what makes me think the sight has got to be wrong.
     
  4. dog2000tj

    dog2000tj New Member

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    From what you are describing it sounds like your sights are mismatched. It sounds like your front sight is too tall, causing the rifle to aim low when you aim. Can you post a picture showing your front sight, top rail and rear sight?

    If you check out Midwest Industries sights you will see that they differentiate between rail and gas block sights.

    I would suggest going back to the shop and discussing this with the smith there. They should be able to recognize the problem right away. If it is mismatched sights than it is a simple fix - install correct sight.
     
  5. ktmboyz

    ktmboyz New Member

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    ok thanks, thats what I thought the problem was, but was unsure if they made two different heights. I will call the shop and see if they will swap it out
     
  6. RL357Mag

    RL357Mag New Member

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    UTG makes an A2 style gas block mounted front sight. This will work with the standard carry handle rear sight. If using a rail mounted rear sight, the lower profile flip type gas mounted front sights should work fine. You can't mix and match.
     
  7. ktmboyz

    ktmboyz New Member

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    I am getting the same results with either my carry handle or the rear flip sight thats why I assumed it would be a mismatched front sight. I'm gona try and call S&W today.. (last time I called about their oem sights he told me about an aftermarket brand that would work on it but I don't remember which it was)
     
  8. RL357Mag

    RL357Mag New Member

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    That's very strange. I ordered a front and rear sight combo from UTG for my flat-top DPMS LR308. The front sight is of the same height and design as a standard A-frame A2 sight, and the rear is a typical rail mounted rear. My rifle's receiver rail is slightly higher in elevation than the front gas block rail, but the centerline of the rear aperature and the top of the front post is level with, and in the same plane as an imaginary line running through the bore. This is all that is necessary. If you remove the bolt and carrier you can insert a long cleaning rod in the barrel which is long enough to pass through the barrel and the receiver, you can measure from the top of the cleaning rod to the top of the front post, and then the top of the cleaning rod to the center of the rear aperature. These measurements must be close to equal when the sights are at the mid-point of their adjustment range. Some rifles make the receiver rail with a slight upward angle to allow bullet drop compensation at extended ranges, but with the sights set at their mid-point adjustment range, the measurement between bore centerline and sight centerline should be almost exactly equal.
     
    Last edited: Jul 15, 2009
  9. indy_kid

    indy_kid New Member

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    Laser!

    Spend $25 or so for a laser boresight. Will save you a LOT of time, effort and ammo. You should have it almost dialed in with the boresight before you get to the range.

    If you use the muzzle type, just remember to remove it (link) before shooting.
     
  10. RL357Mag

    RL357Mag New Member

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    A cleaning rod and a ruler doesn't cost anything, and with an AR, bore sighting is easily accomplished without using ANY tools except your eye's, the way it's done with a bolt action. Separate the upper from the lower, pull the bolt carrier out so you can look down the bore, place the upper on the bench and look down the barrel -center the target in the bore. Without moving anything, look through the scope/sights and see where they are in relation to the target - then adjust sights to place them on target. Done! It may not be as accurate as a laser boresighter, but it will put the first shot on paper...
     
  11. dodge

    dodge New Member

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    Yankee Hill makes a set of sights that will work on your MP 15. They run about $90 apiece. This is what I have on my Stag Model 3 which is pretty much the same thing as the S&W and they work great. You can get them from Brownell's as well as several other places on line.
     
  12. ktmboyz

    ktmboyz New Member

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    Thanks to all for the help!!! I went to a friends shop the other night and he had a couple diff ones there so we matched em up and sure enough there are two different heights. The next day I went back to the store I purchased the gun and sights at and they actually had the one I needed this time and swapped it out no charge. I was kinda surprised because I had bought a utg for $40 and he swapped for a bushmaster one that was $89 and said have a nice day!
    Any way it all worked out for the best, I was able to take my combative rifle class today :D