AR15.Com Archives
 Is this normal (handguards and upper not on the same plane/height)?
JohnCrighton  [Member]
5/5/2009 2:03:54 PM EST
Just installed a pair of brand new DD Lite 7.0 handguards on my flat-top AR. The flat-top's rails are .064" higher than the DD Lite rails. Is this normal? Are there discrepancies in the height of flat-top upper receivers that cause this sort of issue?

Can't recall what manufacturer my upper was made by - either RRA or Bushmaster or perhaps Ameetec. Can't seem to recall off hand. No markings on it that I can see other than a small weirdly contoured letter that looks like an "H" that is wider at the bottom than at the top, and a triangle above the top.
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EDM4  [Member]
5/5/2009 3:05:46 PM EST
If you have a straight rail handguard it should be flush with the rails of your upper. My DD lite rail 7 is straight and level with my upper reciever's rails.
JohnCrighton  [Member]
5/5/2009 3:53:52 PM EST
Originally Posted By EDM4:
If you have a straight rail handguard it should be flush with the rails of your upper. My DD lite rail 7 is straight and level with my upper reciever's rails.


I do have a straight rail handguard, but it isn't flush with the rails of my upper.

One or the other aparently isn't exactly to spec. But my YHM FF handguards that I took off the rifle to replace weren't flush with the flat-top rails either.
EDM4  [Member]
5/6/2009 12:20:03 AM EST
Hmm...maybe your upper is out of spec? If you tried another brand of handguard rail and you got the same problem, I would say the upper is at fault. I have seen gaps between the handguard rail and the upper but they are always on the level. Leveling is needed since sighting systems that will be mounted in these rails needs to be kept aligned and leveled.
nicholsmf  [Team Member]
5/6/2009 2:16:08 AM EST
There was another thread about a DD rail not lining up on here recently. I don't remember what the outcome was. It should line up. Wish I could be of more help but I only use LaRue handguards so I don't know
ManDown  [Team Member]
5/6/2009 2:38:54 AM EST
If you've tried two different rails and they are both above or below your uppers rail, then your upper seems to be the problem. Although it is possible that both rails (forearm rails) are out of spec, but that is just too big of a coincidence.
Strongbow  [Member]
5/6/2009 3:06:40 AM EST
Originally Posted By JohnCrighton:
Just installed a pair of brand new DD Lite 7.0 handguards on my flat-top AR. The flat-top's rails are .064" higher than the DD Lite rails. Is this normal? Are there discrepancies in the height of flat-top upper receivers that cause this sort of issue?

Can't recall what manufacturer my upper was made by - either RRA or Bushmaster or perhaps Ameetec. Can't seem to recall off hand. No markings on it that I can see other than a small weirdly contoured letter that looks like an "H" that is wider at the bottom than at the top, and a triangle above the top.


Who made the upper? It should be flush. Do you have some sort of "Optics Ready" AR with a raised upper receiver rail?
Redtazdog  [Team Member]
5/6/2009 6:43:03 AM EST
Your upper receiver is a older make, before hanguards had rails.
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