KAC URX III 8" rail cover panels

[everyusernametaken]

I've been trying to find the answer to this question to no avail. There are scraps of info scattered around, but I just can't find a definitive answer.

With the URX III 8" handguard, the 3, 6, and 9 o'clock positions are just short rail segments at the forward end of the handguard, and the rest from there back is a shaved-down flat space with screw holes every couple inches. Anyone familiar with these will know what I mean.

So what if I wanted to install a full-length (11-rib, I think) KAC rail cover panel over the 3, 6, and 9 o'clock "rails" of this handguard? I realize they make different cover panels specifically for the URX III shaved rails, but I don't particularly like them. I really like the standard KAC rail covers.

The reason I am wondering if this idea will work is because KAC sells these short Picatinny rail segments that attach to the shaved sections of the rails on this handguard with screws, very similar to the Magpul MOE rail segments. If I attached one of these to the shaved part of the rail, would a rail cover panel fit across both the permanent front rail segment and the removable rail segment to the rear of it?

I'm basically just trying to extend the rail back over the part that is normally shaved flat, just for the purpose of mounting a full-length rail cover over the entire length of the handguard.

[WillHines]

I've been trying to find the answer to this question to no avail. There are scraps of info scattered around, but I just can't find a definitive answer.

With the URX III 8" handguard, the 3, 6, and 9 o'clock positions are just short rail segments at the forward end of the handguard, and the rest from there back is a shaved-down flat space with screw holes every couple inches. Anyone familiar with these will know what I mean.

So what if I wanted to install a full-length (11-rib, I think) KAC rail cover panel over the 3, 6, and 9 o'clock "rails" of this handguard? I realize they make different cover panels specifically for the URX III shaved rails, but I don't particularly like them. I really like the standard KAC rail covers.

The reason I am wondering if this idea will work is because KAC sells these short Picatinny rail segments that attach to the shaved sections of the rails on this handguard with screws, very similar to the Magpul MOE rail segments. If I attached one of these to the shaved part of the rail, would a rail cover panel fit across both the permanent front rail segment and the removable rail segment to the rear of it?

I'm basically just trying to extend the rail back over the part that is normally shaved flat, just for the purpose of mounting a full-length rail cover over the entire length of the handguard.

KAC makes a part that will allow you to do what you want in a more elegant manner.

http://www.operationparts.com/KAC_Knights_SR_16_AR_15_M4_URX_Carbine_Length_p/25124-3.htm

[everyusernametaken]

KAC makes a part that will allow you to do what you want in a more elegant manner.

http://www.operationparts.com/KAC_Knights_SR_16_AR_15_M4_URX_Carbine_Length_p/25124-3.htm

I would definitely prefer to use that rail, but I'm picking up an AAC 9" 300 upper, and unfortunately, it comes with the URX III. It really sucks, because that is the only issue with an otherwise good setup. I was hoping to avoid the need to assemble the upper, and the special KAC wrench and vise clamp, so I don't want to change the handguard on an upper I just bought complete.

I just don't see why they would have shaved the rails on an 8" handguard. Really, how much weight is that saving? I'd much rather have normal rails over a few ounces saved.

[WillHines]

I would definitely prefer to use that rail, but I'm picking up an AAC 9" 300 upper, and unfortunately, it comes with the URX III. It really sucks, because that is the only issue with an otherwise good setup. I was hoping to avoid the need to assemble the upper, and the special KAC wrench and vise clamp, so I don't want to change the handguard on an upper I just bought complete.

I just don't see why they would have shaved the rails on an 8" handguard. Really, how much weight is that saving? I'd much rather have normal rails over a few ounces saved.

I'm not sure its entirely about weight as much as some people preferring the slim grip of a tube style handguard.

As to your original question, though, I've got a URX 2 and 3 and the various bolt-on rails and rail cover stuff. I'll give what you're describing a try and post up the results.

[everyusernametaken]

I'm not sure its entirely about weight as much as some people preferring the slim grip of a tube style handguard.

As to your original question, though, I've got a URX 2 and 3 and the various bolt-on rails and rail cover stuff. I'll give what you're describing a try and post up the results.

Thanks! I appreciate the help.

[WillHines]

No problem, here's what I came up with.

Parts used:


URX 3.1 (I forgot that my URX III upper is with Marvin Pitts, but relevant dimensions are the same)

KAC Deluxe Panel Kit for URX III and 3.1 (rail sections and grips)

URX II

KAC 11-rib rail covers


Bottom line, using the 11-rib panels with a bolt-on rail section and the integrated rails won't work.

http://i1188.photobucket.com/albums/z401/Will_Hines/1.jpg

The add-on rail section is 0.234" off of the handguard plane, vs 0.115" for the integrated rail section.

http://i1188.photobucket.com/albums/z401/Will_Hines/2.jpg
http://i1188.photobucket.com/albums/z401/Will_Hines/3.jpg

The add-on rail section also doesn't have the cut-out to retain the 11-rib panels. If you were to cut one yourself, disregard the integrated rail section, and use the 11-rib covers only on the add-on rails, you'd end up with a pretty wide handguard.

URX 3.1 with add-on rail plus 11-rib panel is 2.73" wide.
http://i1188.photobucket.com/albums/z401/Will_Hines/4.jpg

Compared to 2.46" wide for a URX II with 11-rib panel.

http://i1188.photobucket.com/albums/z401/Will_Hines/5.jpg

And 2.23" for a URX 3.1 with KAC bolt-on panels and 1.93" bare.

http://i1188.photobucket.com/albums/z401/Will_Hines/6.jpg


I know you don't want to change the handguard on a brand new upper, but you might consider this: the price difference between the 7" URX II and the 8" URX III would probably cover the cost of the installation if you were to swap handguards and sell off the URX III.

[rjacobs]

So you just want rail sections to mount rail panel covers to? Seems like a bit overboard(maybe not the right word) when KAC makes grip panels that bolt to the empty sections on the URX III handguard. I wouldnt want to have to try to grab bolt on rail panels plus plastic rail cover panels, would be WAY to big of a diameter for me. I just got a set of the grip panel covers from Operation Parts for like 45 bucks(http://www.operationparts.com/KAC_Knight_s_Armament_Panel_Kit_URX_3_3_1_p/30408.htm). I dont have a pic of mine, but here is one from the 300blk picture thread. Check out post 131 and 133.

https://www.m4carbine.net/showthread.php?t=92862&page=7


I think they are (almost)perfect. My ONLY gripe, and its small, is that I wish the hand stop was further back, possibly back at the rear mounting screw with the screw sunk down through the hand stop. It seems to push my hand a little far forward to where my grip on the side rail panels is pretty far forward and the front of my hand is off of the grip panels, although just barely. I also have a Streamlight TLR1 mounted on the left side and it kinda jams my hand and everything in a bit tight. I may have to move the TLR1 up top and move my BUIS back a few notches, although I would prefer not to. Might move it to the bottom and see how that works out. Or I may just get used to it and figure out a hand position that works better for me. They include a panel that doesnt have the hand stop on it, but I really want to try to make the hand stop workout. It felt better yesterday moving the gun around with the handstop than it did prior to having the grip panels on.

I honestly dont see why KAC doesnt just include these with the rail system personally. I can kind of understand why they dont include all the rail sections(to me they arent needed and are probably WAY more costly to produce), but these grip panels simply finish off this hand guard perfectly.

[everyusernametaken]

Thank you for the very helpful info and pictures. That is precisely what I was hoping to do, and precisely what I worried the result would be! :D

I didn't realize the carbine-length URX II is only 7". I like the AAC 9" upper for the perfect combination of 9" barrel and 8" handguard, and pretty much no gap to the suppressor. I think I'd have to give this priority over the rails. Maybe I should just give the upper a try with the URX III that it comes with, and see if it grows on me.

Wish I could get the best of both handguards, but looks like I have a conundrum. :confused:

I really appreciate the help! The detailed pictures and measurements were exactly what I needed. I would never have found one near me to check it out myself.

[genofromreno]

Sorry to hijack...................

WillHines this question is for you (maybe you might know):

I'm looking to upgrade my KAC SR-15 M4 (SBR'd to 10.5in) that currently has a KAC FSGB and KAC M4 URX Carbine Length. I want to swap out the KAC M4 URX Carbine Length (7 3/16ths Length) for the KAC URX3 8.0 (8" Length).

1. Do you know if this will work? There is a small gap now between the FSGB and URX.

2. Would the front of the KAC URX3 8.0 have to be shortened or the rear "timed" quite a bit?


I haven't seen anyone use the URX3 8.0 on a carbine yet, and I'm hoping that I can.

Thanks in advance, Geno

[WillHines]

I'm sorry, I can't say for sure. Like you, I've never seen a URX III / FSB combo. Thinking aloud, though, it would be an interesting project needing a fair amount of work.

I can't imagine the gap between the URX II and the FSB is 13/16ths wide and you won't want contact between the two, so you are probably looking at nearly an inch of metal removed.

Marvin Pitts or Wes at MSTN would probably be better able to answer URX cutting questions.

[genofromreno]

I'm sorry, I can't say for sure. Like you, I've never seen a URX III / FSB combo. Thinking aloud, though, it would be an interesting project needing a fair amount of work.

I can't imagine the gap between the URX II and the FSB is 13/16ths wide and you won't want contact between the two, so you are probably looking at nearly an inch of metal removed.

Marvin Pitts or Wes at MSTN would probably be better able to answer URX cutting questions.

Thanks Will for the reply, I shot out a few emails yesterday and got some replies back and it's looking like it may not work.

A) cuts on the front wouldn't work aesthetically with the position of the rail vent holes. (still possible, just may look odd).

B) and doing some extreme timing would interfere with the barrel nut and its positioning to the bottom of the forend for installation.

I haven't totally given up yet, all the parts are waiting for me back home (I'm in Afghanistan right now), but it would be nice if it works out. Thanks again.

[WillHines]

I haven't totally given up yet, all the parts are waiting for me back home (I'm in Afghanistan right now)


That's the worst! I had all the parts waiting for a couple projects for months before I got home to work on them. The silver lining is, by the time you get home, you'll have forgotten you ordered a couple small things. Its like opening presents. :D

Stay safe, man.

[genofromreno]

Awesome, thanks man!