First post for the FNG!! 
I just bought a Knight’s Armament Company RAS for my DPMS, and am having a hell of a time getting it on. I have put KAC rails on M4’s in Iraq, but those were Colt’s and thy seemed to be made for each other…
Can someone give me some advice/hints on what I may be doing wrong? Or am I SOL, and KAC RAS rails just don’t fit on DPMS AP4 carbines?..
Grappler
They should fit fine as far as I know. Hopefully someone with more knowledge will come along…
Here’s the problem I am having right now. The bottom rail goes in fine, but the top rail isn’t wanting to go in to the ring under the front sight post. There is a clip on the RAS and I can’t remember if the clip goes into the ring or above it…
Try removing the top screw all the way and then getting the latch under the inside of the bbl nut. then reinstall.
The small leaf spring on the front of the RAS goes into the handguard cap not on top of it. It provides tension to tighten up the RAS. There are pictures floating around on TOS of USGI M4s with the leaf spring sitting on top of the handguard cap. While it will fit that way, that is an incorrect installation.
See page 3, subsection 3 on this PDF link:
http://www.quarterbore.com/library/pdf_files/kac_ras_inst.pdf
Thanks for the info guys. I’m currently reading this at work, so I can’t play with the weapon to see if this will work…
Do any of you have a KAC RAS on a DPMS AP4?
I’d like to hear from someone who has actually had to put this type of handgaurd on this type of rifle. I’ve been searching like a mad man to get an answer on this and on another board, I was told I it would not work and that I should go ahead and sell it…:mad:
You’ll not likely find a lot of DPMS owners on this site.
Ahhh…Thanks for the heads up.
Why won’t they fit a DPMS?
Well, I couldn’t get them to fit it, so I took it down to the local gun shop to turn in to the gunsmith who may have to make some modifications to it…:mad:
I’d buy a quality upper before I let some hack screw with my quality gear. From a practical standpoint the RAS is worth more than the DPMS upper.
No worries…He’s going to assess it and give me a price on how much the mods will cost. I’m currently talking to a buddy of mine who is willing to trade the DPMS for his Colt competition H-Bar. So, if that works out, I won’t have to deal with this…
I don’t understand what DPMS could have done that would make it not work-
triangular handguard cap? They should work with those anyway but then again, M4s probably all had round ones when built.
Don’t let that smith Bullshit you either. Make sure you tell us what he says before you let him proceed.
The only other mount point would be the barrel nut and those are the same or should be as well…
Barrel profile?
Lipstick on a pig, Baby!
Ouch…(true however).
There is a spacer on the front of the RAS that sits atop the gas tube and the barrell. This is where the problem lies, as the spacer makes it impossible to get the leaf spring and the lip insert into the handgaurd cap.
The gunsmith is probably going to have to file the space down a bit to the front to go in.
My .03 cents. As an armorer I rarely file or grind anything with exception of crap AK’s and PKM’s. If your gun is new or like new and the KAC RAS is new or like new I wouldn’t be too happy about some gunstore “gunsmith” filing something down. I have installed dozens and dozens of rails on M4’s and M16A4’s with no problems. I have seen issues with BM also not fitting right. Bottom line is you may be better off with a different rail.
SuicideHZ
I don’t understand what DPMS could have done that would make it not work-
triangular handguard cap? They should work with those anyway but then again, M4s probably all had round ones when built.
You dog out Bushmaster, but act surprised over DPMS…:rolleyes:
Spacer? can you post pictures of said spacer? the only spacer i’ve ever seen with the RAS is the M203 adapter that comes with the M5 RAS. is it a silver metal horseshoe shaped piece with two little springs on either ends?
Sorry brother, the wife has the digital camera. Let me see if I can describe it for you…
You have to put the top piece in first, front end first. The spacer is a lower case “n” shape that wraps around, or better yet, goes over the gas tube and sits right on the barrell. That’s where the problem is. Because the spacer is a centimeter(geussing) to big, it will not slide into the front sight, handgaurd cap.