i have a knights rail m4 but it seems to sit a little higher than my flat top a3 and seems to be off cant a little if looking fron the chmber to muzzle seems like it needs to go a little left how can i get this to line up
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i have a knights rail m4 but it seems to sit a little higher than my flat top a3 and seems to be off cant a little if looking fron the chmber to muzzle seems like it needs to go a little left how can i get this to line up
We had somebody here just recently with a similar problem Is the gas tube lined up straight?
if the rail is canted then the barrel nut isn't lined up correctly as well (unless you have a defective RAS but I dont think this is the case)
I remember the other guy who posted this too.
I still don't see how it's mechanically possible. The gas tube goes in the upper at top dead center. The barrel nut has to line up to the gas tube hole. And the KAC rides the gas tube with the latch straddling the tube on either side.
The gas tube hole in the upper would have to be off center for any of this to get out of whack.
you guys talking about the larue rail? i was really hoping to get my hands on it... but now i'll just have to dissassemble one to try to duplicate. going from memory, and the diagram of larue's installation instructions, i just dont see how it's possible either..
it's kind of driving me nuts
HOW off is it? can you get a pic of the rails long-wise? i've never done a KAC rail, so i don't know how they attach.. but generally, if it's just off by an emem or so, just loosening up the screws or lockring or whatever holds it on, bridging the gap with a rise or mount or something, and tightening it back down will fix it.
:confused:only problem I had with my KAC hand guard was I didn't have a hand guard tool top rail went in fine after I removed the locking screw. The bottom rail I cursed for about 2 hours before it finely slipped in very next purchase was the hand guard tool [ I am not going through that mess again if I can help it]
markm right i would think that the barrel nut not being timed right would bend the gas tube and cause a problem with the gas key.
This is not an airsoft kac rail is it. Just asking ..
What profile is the barrel ??
I think the KAC is only designed for the GI profile barrel.
http://www.bushmaster.com/images/cat...-BBL-14M4A.gif
http://www.bushmaster.com/images/cat...BBL-145AKA.gif
Bushmaster uses a couple of different profiles is it thin or heavy
The barrel nut needs to be reset a little bit at a time until the RAS affixes to the rifle in top dead center.
The gas tube has enough flexibility in it that the barrel nut can still be off by +/- a few degrees.
Did you make sure the latch that markm is talking about--the one that straddles the gas tube--is correctly underneath the delta ring? Take the screw out of the top rail completely and install the top rail in a top up, horizontal fashion rather than holding the rifle vertically on a table to depress the delta ring. This should allow gravity to pull the latch down to clear the delta ring (as long as you have it pushed forward enough of course). I installed one on a bushmaster without a problem, but given their "issues" YMMV.
In the past I had tried to install some KAC's on Bushmasters and there was a slight fitting problem. Not sure where the issue was.
Have you contacted the MFG (KAC) to see if it is a KAC problem or a BM problem? There is a KAC rep on this board you know.
Do you perhaps have another rifle you can try it on?
Very very true.
Companies that do not get our M4 or M5 RAS on them generally do not take a great deal of time ensuring the barrel nut is clocked 100% - it will work fine for a plastic handguard, but not necessarily so for a railed handguard.
The other issues is we make our rails for a MILSPEC barrel -- Colt and FN (us, LMT and Sabre too I beleive) since BM is not a 1st article producer - it is impossible to tell what profile they have decided to use.
While in Iraq contracting, I saw many many manufacturers rifle and carbines that would not take a USGI KAC rail, despite their claims to the companies that bought them...
thanks for the info direct did you see the article on kac info here that is posted
https://www.m4carbine.net/showthread...0&goto=newpost
A bushmaster barrel should be able to accept a KAC handguard as their barrels are profiled to the Colt pattern.
As a side note, you probably don't want to use a rail mounted front sight on the M4 RAS anyway. The rail is pretty secure, but it will move no matter how well of a fit there is. Even if it were completely secure, you would have a shortened sight radius. You might want to get a barrel mounted sight or FF RAS instead.
Dustin
I think I have the same issue the OP has.
My upper's by Stag, but the height difference is very minimal. I'm starting to think it could be the barrel nut being off by a few degrees, but the RAS is securely attached.
Fortunately, this isn't really an issue since I don't bridge my optics from the upper to the RAS.