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Posted by Tom P. regarding the new 2014 Knights rifles-

In light of recent discussions it has become apparent that some observers have not been sufficiently informed of the system alterations that KAC has implemented in the 2014 line. We would like to explain these system updates and what prompted these changes.

The gas system was designed primarily to eliminate gas leakage at the gas block and gas tube/gas block interface. Most issues with function in the Stoner-designed internal inline piston operating system are linked to management of propellant gas pressure. The traditional pinned-in gas tube is susceptible to pressure loss at the gas block/gas tube interface point. This can easily be observed on legacy systems at the gas tube/gas block juncture, evidenced by carbon build up. Inconsistent pressure bleed in the gas system forces the AR system to be intentionally over-gassed to ensure reliable function with a variety of ammunition in varying environments and conditions of fouling. In traditional systems the gas-bleed will eventually self-seal via carbon build-up, resulting in even greater system pressure. Adding a suppressor further increases system pressure and duration of pressure, which can cause other function issues due to increased bolt carrier velocity. The fitting of the gas-tube to the gas block spigot, with positive retention by a specifically torqued nut, eliminates early loss of pressure, permitting the system to reliably operate in the afore-mentioned conditions without over-gassing. Sealing bleed points enables KAC to continue to produce carbines that are soft-shooting and highly reliable while reducing the potential to have the occasional under-gassed carbine reach the consumer. Straight gas tubes can be tightly controlled and are not susceptible to deformation or pinching during production as traditionally bent tubes are. The straight tube aligns with the gas key of the bolt carrier with greater consistency than bent tubes as well, significantly reducing the need to tweak tube alignment.

The castle-nut type of retainer nut was chosen over other retention methods such as taper pins and set-screws. Taper pins are a very secure method of gas-block assembly, however, they do come with some negatives. Taper pins are one-time use items as they are usually deformed during the installation and removal processes. The zero-tolerance fit of taper-pins to the gas block and barrel marries the barrel to the gas block; loss of the gas block for any reason will preclude the use of another taper-pinned gas block unless meticulously selected. Drilling the barrel and gas block for taper pins introduces a possibility of barrel distortion, and while not necessarily noticeable, does impact barrel rigidity. The revised gas system’s gas block is interchangeable without fitting, and the retaining nut can be reused. No holes need to be drilled into anything, and assembly/disassembly no longer comes with potential damage to the gas block or barrel. Set screws can potentially loosen, even if seated in dimples in the barrel, and when torqued and sealed into position have a tendency to strip during disassembly. The castle nut type retainer nut of the revised KAC gas system can bear high disassembly torque, and when properly torqued to design, are not susceptible to loosening during use.

The URX4 hand-guard system stands apart from most other visually similar fore ends in that it is a progression of the Integral Barrel Nut (IBN) concept; a fresh approach to rigidity, modularity, simplicity, and weight reduction. Having the hand-guard and barrel nut as a single unit results in a monolithic-like extension of the upper receiver once properly assembled. The integrated barrel nut of the URX4 virtually eliminates the need for specialized tools to assemble or disassemble the system. The one-piece tubular design is more rigid than multiple joined sections forming the hand-guard, providing less POI deviation with hand-guard mounted sighting systems if lateral forces are applied, and sheds the weight of the assembly hardware. Thermal transfer away from the chamber area is improved with the IBN system, and enhanced with the natural cooling and air-flow of the KeyMod mounting point openings. KeyMod recesses distributed around the hand-guard provide compatibility with industry standard mounts without the weight and bulk of MIL-STD-1913 rails. Mounting points are available on seven sides of the hand-guard for optimal placement of accessories, with the 12:00 portion devoted to a MIL-STD-1913 rail for aiming devices. The outer diameter of the URX4 is very similar to the URX3/3.1, but with a larger internal diameter to enable clearance for indexed suppressors. Weight of the 14.5 inch 5.56 URX4 is lower than that of the 13.5 inch 5.56 URX3.1, giving the user more barrel protection, more mounting options, and longer sight radius with no weight penalty. Clearance for the improved gas systems of the SR-15 E3 Mod 2 and SR-25 E2 have been accounted for and integrated into the URX4 to ensure that the barrel and gas system are free-floated inside the fore-arm.











Some URX 4 keymod accessories-




Ambi charging handles



New QDC cans



More photos can be found here - Knights Armament @ SHOT 2014 by SMGLee


I'm still a little upset that they are depreciating the MOD 1 line though... Can't have everything I guess.
 

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Just can't like the new UXR4, not a fan of the "key mod" reminds me of the shelving interlock system I see a Lowes. I also don't understand why they felt they needed to go with AN style fittings for the gas tube to gas block and a castle nut to retain the gasblock. Just seems like alot for the minor "improvements".
 

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Just can't like the new UXR4, not a fan of the "key mod" reminds me of the shelving interlock system I see a Lowes.
But it does make attaching stuff easier that Troy's fore-ends or similar ones. They're growing on me.

And they're using B5 Systems stocks now?
 

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I wish they didn't discontinue the E3 Legacy. I really wanted one of those.
 

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Just can't like the new UXR4, not a fan of the "key mod" reminds me of the shelving interlock system I see a Lowes. I also don't understand why they felt they needed to go with AN style fittings for the gas tube to gas block and a castle nut to retain the gasblock. Just seems like alot for the minor "improvements".
Agreed but, like it or not, I think we'll be seeing more of it as AR's get "slimmer and trimmer". That's all the rage now....taking them back to where they started, sort of. KAC, and several other high end makers, are really fighting the piston trend tooth and nail.

To the OP, speaking as a person who was making flat top AR's with tube handguards in the mid 80's, I'd take a SCAR 16s over any "legacy" AR.
 

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And they're using B5 Systems stocks now?

LMT SOPMOD still, haven't seen any come with the B5 stocks yet.


I tried the Noveske NSR rail and just wasn't a fan, ultimately I like the KAC URX 3.1 and the Geissele MK4 style but I'm also pretty happy with the RAS FF and Daniel Defense sh!t.
I get alot like the thinner profile and the ease of the "Key Mod" attachments, I feel it more a marketing deal, easier to make and only slightly stronger or an improvement.
 
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