View Full Version : KAC mod 2 gas system lengths
Does anyone know what gas systems are used on SR-15 mod 2's and if they are proprietary, how long are they?
The whole system is proprietary. The gas block is locked in with a castle nut and the gas tube has a pneumatic style connector sort of thing.
I think the gas port is like 11.2" or 11.5" from the standing face of the receiver. Very similar to the intermediate length offered by other manufacturers.
Knights calls it “a proprietary mid-length gas system” but as others have stated, it’s more like a intermediate. Below is an excerpt from Knights Armament’s description. The link is at the bottom.
“The Knight’s SR-15 Mod 2 line represents the pinnacle of firearms based upon the Eugene Stoner designed operating system. The Mod 2 update introduces several notable features to the SR-15 IWS line. The chrome lined 5.56mm NATO barrel features a proprietary mid-length gas system that increases reliability and durability while also reducing felt recoil. The Mod 2 gas system minimizes the chances of gas leakage and ensures more consistent operation in harsh conditions. The new gas block is secured with a locking ring instead of taper pins, which increases barrel rigidity and eliminates the need to custom fit the gas block to the barrel.”
https://www.knightarmco.com/4685/shop/commercial-firearms/sr-15-carbine-mod-2-2
Failure2Stop
01-19-18, 11:32
Does anyone know what gas systems are used on SR-15 mod 2's and if they are proprietary, how long are they?
Is there a particular reason that you ask?
I might be able to help cut to the chase.
Want a pic rail on instead of Mlok or KM. I know there are clearance issue with the new gas blocks. I'd like to put a RIS II on it, but if the gas block sticks out or it just doesn't fit, I'll leave it as is probably.
Edit: I am wondering on a 14.5in. Will the RIS II cover the gas block?
pointblank4445
01-20-18, 16:16
Want a pic rail on instead of Mlok or KM. I know there are clearance issue with the new gas blocks. I'd like to put a RIS II on it, but if the gas block sticks out or it just doesn't fit, I'll leave it as is probably.
You'd need to know the size of the top of the gas block where it bolts up and how much clearance the top rib/channel of the rail has to be to allow for the bolt-up gas system. If the rail you intend to use has the same or more generous internal dimensions than the URX4...you'd be good to go. I too have contemplated doing something similar in putting a 3.1 on an ACC and the same on the SR15 with a Mk1 Geissele rail.
Knights calls it “a proprietary mid-length gas system” but as others have stated, it’s more like a intermediate. Below is an excerpt from Knights Armament’s description. The link is at the bottom.
“The Knight’s SR-15 Mod 2 line represents the pinnacle of firearms based upon the Eugene Stoner designed operating system. The Mod 2 update introduces several notable features to the SR-15 IWS line. The chrome lined 5.56mm NATO barrel features a proprietary mid-length gas system that increases reliability and durability while also reducing felt recoil. The Mod 2 gas system minimizes the chances of gas leakage and ensures more consistent operation in harsh conditions. The new gas block is secured with a locking ring instead of taper pins, which increases barrel rigidity and eliminates the need to custom fit the gas block to the barrel.”
https://www.knightarmco.com/4685/shop/commercial-firearms/sr-15-carbine-mod-2-2
Isn't the gas tube connected with a Flare connection?
I too have contemplated doing something similar with an SR25 and the SR15 and a Mk1 Geissele rail.
I didn't consider that, but that would be very interesting. Wasn't there a 13" Mk1? That on a 14.5 would be probably better than what I am thinking :D
pointblank4445
01-20-18, 18:00
Isn't the gas tube connected with a Flare connection?
This is the Mod 2 system:
http://cdn3.bigcommerce.com/s-xock0/products/3356/images/5894/31030-6__88430.1475081954.1280.1280.jpg?c=2
Isn't the gas tube connected with a Flare connection?
AN type fitting, yes
Failure2Stop
01-20-18, 20:48
Want a pic rail on instead of Mlok or KM. I know there are clearance issue with the new gas blocks. I'd like to put a RIS II on it, but if the gas block sticks out or it just doesn't fit, I'll leave it as is probably.
Edit: I am wondering on a 14.5in. Will the RIS II cover the gas block?
It won't fit due to the height of the gas block. That said, you could simply attach rail sections at the 3, 6, and 9 and get the same effect, with no need to wrench on the gun.
It won't fit due to the height of the gas block. That said, you could simply attach rail sections at the 3, 6, and 9 and get the same effect, with no need to wrench on the gun.
Lol @ leaving rail sections without using them. Kinda defeats the purpose of Mlok.
Mr. Goodtimes
01-20-18, 21:35
Why the hell would you want to replace the URX 4 rail? If you want a pic rail go seek out a Legacy rifle.
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Mr. Goodtimes
01-20-18, 21:37
Lol @ leaving rail sections without using them. Kinda defeats the purpose of Mlok.
It’s a lot less stupider than wasting the time, money, effort and brain cells to replace a perfectly good rail system off a perfectly good rifle and replacing it with another rail system that literally does the exact same thing.
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pointblank4445
01-20-18, 22:15
It won't fit due to the height of the gas block.
The top rail/upper doesn't sit any higher on a KAC than any other AR (unlike say an HK 416)...just how much more clearance does the URX4 have given that some others on the market are rather generous. I always wished KAC were more forthcoming with their dimensions and specs...
Why the hell would you want to replace the URX 4 rail? If you want a pic rail go seek out a Legacy rifle.
The legacy stuff is stupidly priced on the open market. In my case, I could have bought an ACC, a URX 3.1, and pay Marvin handsomely to change it out for what an ECC would have cost. Or how bout a nice used Mod 1 for $2.7k (https://www.gunbroker.com/item/739926012)? I also enjoy seeing what some of the Grade B EMC's are being priced at when they turn up from time to time...
I really like what KAC has going on under the hood so to speak in terms of barrels/BCG's and what not, but I have issues with other aspects...one being the URX4. Just because YOU don't understand something doesn't mean the concept is any more or less valid. But you are right though...ultimately trying to cram the square peg in a round hole just wasn't worth it.
Lol @ leaving rail sections without using them. Kinda defeats the purpose of Mlok.
Says the genius that wants to replace an MLOK rail with pic...
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I don't like Mlok or keymod
Mr. Goodtimes
01-20-18, 22:34
I don’t like you. How dare you bastardize Eugene Stoners masterpiece.
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I forgot about the time he made Mlok or Keymod
Mr. Goodtimes
01-20-18, 22:57
I forgot about the time he made Mlok or Keymod
I hope the ATF kicks down your door and takes your SR-15’s.. You don’t deserve them. I hope they screw up your lawn too.
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This is the Mod 2 system:
http://cdn3.bigcommerce.com/s-xock0/products/3356/images/5894/31030-6__88430.1475081954.1280.1280.jpg?c=2
There's a meme for unnecessary complexity out there somewhere...
I don't like Mlok or keymod
So you’re crying about defeating the purpose of MLOK, but you don’t like MLOK so you want to switch it to something that will achieve exactly the same endstate, minus the option to easily change it back?
If you didn’t like MLOK, why’d you buy the gun?
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So you’re crying about defeating the purpose of MLOK, but you don’t like MLOK so you want to switch it to something that will achieve exactly the same endstate, minus the option to easily change it back?
If you didn’t like MLOK, why’d you buy the gun?
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I don't have one. I have a RIS. I wanted to know if the gas block would be too long and stick out, or if it would fit at all. I may not like mlok, but I don't see why I would just leave rail sections on at all times. I like pic rails because the rail sections are one piece with the rail, and then whatever you want is clamped onto that. In my experience it has been considerably more solid using a good quad rail than pretty much anything else.
Jack, thank you for your help. I'm glad you are so active on this and other forums.
This is the Mod 2 system:
http://cdn3.bigcommerce.com/s-xock0/products/3356/images/5894/31030-6__88430.1475081954.1280.1280.jpg?c=2
And YES, it is a flare fitting on the tube. This to me makes way more sense than a pinned tube. A flare fitting is a proven method to withstand large amounts of pressure.
http://www.operationparts.com/knights-armament-mid-length-gas-tube-for-the-sr-15-14-5-16-mod-2-11-7-8-long-long/
49951
49952
And YES, it is a flare fitting on the tube. This to me makes way more sense than a pinned tube.
Yes and no. If carbon gets in the threads, it will make removing the AN fitting more difficult. Yes, carbon CAN work its way into the threads. Yes, there are steps that can be taken to prevent this.
I forgot about the time he made Mlok or Keymod
And the time he invented picatinny.....
There's a meme for unnecessary complexity out there somewhere...
Naw......it’s a better mousetrap
The top rail/upper doesn't sit any higher on a KAC than any other AR (unlike say an HK 416)...just how much more clearance does the URX4 have given that some others on the market are rather generous. I always wished KAC were more forthcoming with their dimensions and specs...
I think the point he was trying to make is that the height, width and radius of the Mod 2 gas block will not work with a non URX4 rail. Internal structure of the older rails is the factor that limits the use.
pointblank4445
01-21-18, 12:46
I think the point he was trying to make is that the height, width and radius of the Mod 2 gas block will not work with a non URX4 rail. Internal structure of the older rails is the factor that limits the use.
I know that; I thought I made that clear in the portion you quoted.
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