View Full Version : DD RIS II and Intermediate Length Gas System
I’ve searched around and haven’t found anything definite.
I’m wondering if the DD RIS II, the 12.25” model will fit over a barrel with an intermediate length gas system.
I was going back and forth between the Lite 12.0 (12.65") and the RIS II. I like the profile better of the RIS II. The Lite is open at the muzzle end, while the RIS II is partially enclosed. I’m worried this little section which serves to close off the end of the RIS II will make contact with the gas block (Novekse/Vltor low-profile).
I use the Mk18 RIS IIon a DD CHF 14.5" mid-length... Other than about a half inch of projection of the low profile gas block, it fits fine. I think the M4 RIS II will work, and cover the gas block completely. You just need to use a low profile GB...
Do youmeanthe KAC intermediate gas system?
Im looking at photos of a middy with a RIS II M4 and a 16 KAC sr15 and it looks Like you should be just fine. It will be close but it should settle just behind the RIS II's chin.
Worst case scenario, again, purely from photo comparisons, You'll have to dremel the GB's front a bit. Not hard to do and it doesnt take much to clear the chin. I have the same set up as Tom but with a 16 middy and a standard GB which I had to dremel at the rear to clear the rail. Took me 15 minutes max, 10 of which was mostly due to my OCD's serious need to make things even.
What pic are you looking at?
I am talking about the intermediate length gas system, longer than a mid-length, shorter than a rifle.
Its a MSTN/Noveske barrel, but yes, very close if not the same as the KAC gas system.
I was just wondering about clearing the chin (I like your description of it) of the RIS II.
The front of my gas block has a slight angle to it, looks just like the stainless one in the third pic in this thread from TOS...
http://www.ar15.com/forums/topic.html?b=3&f=124&t=521661&page=1
I wasn't aware of the length of the intermediate gas system... but, if it's any further forward than a mid-length then you might run afoul of the rails forward opening or in the case of the RIS, the key-hole. My experience is with a DD low-pro pinned gas block which is fairly minimal in it's footprint on the barrel, and it fits well through the key-hole of the RIS II. I couldn't tell you if the other types of gas blocks would work the same. As the others have stated, you may have to mod the gas block to clear the front opening of the RIS because it is smaller.
the gas port on a noveske intermediate is at 11.5" from the face of the receiver. so a handguard that goes out to 12.0" will cover about half of a noveske/vltor style gas block, the other half will stick out. if it's pinned, it matters not.
There was a pic on militarymorons of a intermediate gas system with one of the 12.0 Lite rails. It looked as if the gas block was about 1/4-1/2" from the end of the handguard.
Where this gets fuzzy is that there are different specs listed of the rails depending on the source. IIRC, the 12.0 Lite is actually 12.65" and the RIS II is 12.25".
I'm thinking if the RIS II fits, it's going to be very close. I had ordered one from Brownells. I may have to call them in the morning and change it to a Lite.
Just in case anyone else decides to try this combo out, it DOES fit. Plenty of clearence between the gas block and rail system. I was worried that the lower lip of the rail would make contact with the gas block. There is actually a decent gap there, where the gas block could pass completley through the opening.
Funny thing is the manual lists the rail as 12.57". Mine was date coded Aug 2010.
Very happy with the rail.
http://img.photobucket.com/albums/v340/roguedemon/IMG_0358.jpg
http://img.photobucket.com/albums/v340/roguedemon/IMG_0359.jpg
http://img.photobucket.com/albums/v340/roguedemon/IMG_0361.jpg
Find ManBearPig!
03-10-11, 18:44
Just in case anyone else decides to try this combo out, it DOES fit. Plenty of clearence between the gas block and rail system. I was worried that the lower lip of the rail would make contact with the gas block. There is actually a decent gap there, where the gas block could pass completley through the opening.
Funny thing is the manual lists the rail as 12.57". Mine was date coded Aug 2010.
Very happy with the rail.
http://img.photobucket.com/albums/v340/roguedemon/IMG_0358.jpg
http://img.photobucket.com/albums/v340/roguedemon/IMG_0359.jpg
http://img.photobucket.com/albums/v340/roguedemon/IMG_0361.jpg
Thinking about getting one... is it worth the extra money and weight over the light rail?
RAM Engineer
03-10-11, 18:49
Thinking about getting one... is it worth the extra money and weight over the light rail?
To me, the best thing about the RIS II over the Lite Rail is the tucked up 6 o'clock rail. They also have anti-rotation stops and removable lower rails if those things are important to you.
KAC RIS/RAS
Larue Tactical
DD RIS II
^^^These are the only rails that have bottom rails tucked up close to the barrel. I like 'em.
Find ManBearPig!
03-10-11, 18:52
To me, the best thing about the RIS II over the Lite Rail is the tucked up 6 o'clock rail. They also have anti-rotation stops and removable lower rails if those things are important to you.
KAC RIS/RAS
Larue Tactical
DD RIS II
^^^These are the only rails that have bottom rails tucked up close to the barrel. I like 'em.
So, how would you say the DD compares to the KAC rails? Also, will I ever actually need the removable bottom?
So, how would you say the DD compares to the KAC rails? Also, will I ever actually need the removable bottom?
your barrel WILL rust underneath the handguard, if you never clean and oil it.. so removable bottoms are great just for being able to jam an oily rag up in that bitch and wipe 'er down.
even for stainless barrels, it's good to be able to oil it from time to time. no steel is truly 100% "stainless"
Find ManBearPig!
03-10-11, 18:56
your barrel WILL rust underneath the handguard, if you never clean and oil it.. so removable bottoms are great just for being able to jam an oily rag up in that bitch and wipe 'er down.
even for stainless barrels, it's good to be able to oil it from time to time. no steel is truly 100% "stainless"
Great point. I think this answers all my questions about the DD RIS II besides how it compares to the URX. Thanks for the help.
Worth is kind of subjective. The DD rail is only a few ounces heavier, but about twice the cost. The DD RIS-II is a beautiful peice of machine work. The bolt-up system it uses, IMO, is vastly superior to the TRX.
Unless you are obsessed with going as light as possible, the DD offers a lot more capability. I like the DD RIS-II more than the TRX Extreme, but there are plenty of people who are happy with the TRX.
The DD Lite series are not much heavier than the TRX...the RIS-II being slightly heavier than the Lite.
Find ManBearPig!
03-11-11, 20:04
Worth is kind of subjective. The DD rail is only a few ounces heavier, but about twice the cost. The DD RIS-II is a beautiful peice of machine work. The bolt-up system it uses, IMO, is vastly superior to the TRX.
Unless you are obsessed with going as light as possible, the DD offers a lot more capability. I like the DD RIS-II more than the TRX Extreme, but there are plenty of people who are happy with the TRX.
The DD Lite series are not much heavier than the TRX...the RIS-II being slightly heavier than the Lite.
Not sure who asked about the Troy, but I generally don't compare the DD rails to the Troy TRX, as I see the DD is a full on rail system, while the Troy as more of a really nice modular handguard that you can mount optics on. Of course, the DD mount does seem superior.
Anyhow, excellent points none-the-less. I may need to go to my local AR shop, and after asking them why they sell RRA bolts as standard with their uppers, get my sweaty palms on the rails to examine them individually. I wish I could own a bunch AR's with a bunch of different rail systems on them and shoot them regularly, but then again we all do. :D
Anyhow, I appreciate the thoughts on the rails from you guys. I'm still not sure what I want on the upper I'm still conceptualizing, and this helps alot.
english kanigit
03-11-11, 20:32
While this topic is up...
I assume that a FSP shaved down would fit under a RIS without issues? Would the bayonet lug and sling swivel holes need to be whacked off as well?
Thanks,
Ek
There are a few different RIS-II systems.
The M4A1 FSP will fit the full un-changed FSP.
https://danieldefense.com/rail-systems/ris-ii/m4a1-fsp-rail-interface-system-ii-ris-ii.html
The M4A1 (the one I have pictured) is meant for a low profile gas block. From looking at mine, I don't think you'll have enough room for the bayonet lug etc.
And of course the MK18 one, which is a shorter 9 1/2" rail, otherwise the same as the longer M4A1.
Some places selling them call them all RIS-IIs. I scoped mine up because I was looking/waiting for quite a while to find one in black.
english kanigit
03-11-11, 20:51
I understand the difference between the rails, I was planning on installing the same model you have.
Right now it has an 12.0 OMEGA-X FSP. The issue is that the flash hider is perm attached. Fortunately DD uses the same barrel nut for all of their rails. I'm planning on pulling the barrel assembly, installing the lockup plate for the RIS and then re-installing the barrel assembly and slapping on my new rail. I'm just trying to think ahead for how much of the FSP is going to 'sacrificed'.
Ek
When I first fitted my carbine with a Mk18 RIS II, I shaved every non-essential piece of metal away from the original FSB. Luckily, I work in an aviation shop and we have access to some useful tooling... pencil grinders w/ cobalt burrs and industrial belt grinders as well as media blast cabinets... after I finished, it looked like the skeleton of its original form. Then i had a buddy that has a setup for redoing the manganese phosphating so, it looked factory after it was done. It had a lot of room inside the rail and there was never any issue of it coming in contact with the rail. Iraqguns is now the owner of that barrel and I have since changed out for a 14.5 chf midlength gas system barrel from DD. It can be done if you have some basic tools and a way to refinish the project once you are done, and you won't have to worry about your gas block turning.
Not sure who asked about the Troy, but I generally don't compare the DD rails to the Troy TRX, as I see the DD is a full on rail system, while the Troy as more of a really nice modular handguard that you can mount optics on. Of course, the DD mount does seem superior.
Sorry, when you said light rail I assume your meant lightweight TRX style not the DD Lite. Brain fart.
I've owned both the DD RIS II and the Lite, in addition to the TRX. For what it's worth, I like the RIS-II the best so far.
Find ManBearPig!
03-11-11, 22:48
Sorry, when you said light rail I assume your meant lightweight TRX style not the DD Lite. Brain fart.
I've owned both the DD RIS II and the Lite, in addition to the TRX. For what it's worth, I like the RIS-II the best so far.
All is forgiven. :D
Thanks for the advice. Looks like the best option is still going to go to my local shop, tell them to stop including RRA bolts with their uppers, and screw around with the rails I'm interested in... if they would only stock KAC, and if only KAC would let them...
If anyone is interested in the place, here is a link. http://www.parallaxtactical.com/store/
I want them to do well, and the last time I went there is when I was uneducated about AR's, so I'll see what's changed. They have started a AR based store in Kommifornia, and for that, they have my utmost respect. However, I'll have to see what they say when I ask why they are not using better barrels, better parts, or at least DD or BCM bolts, something they should easily be able to get and are not much more money than RRAs. They could at least buy a MOACKS if it came down to that...
Sorry to stray of topic. Just wanted to vent that. Hope no one minds.
Do the 203 hangers have to be removed for a midlength gas block?
Intermediate is not the same as mid-length.
That being said, the M203 hangers have to be removed to clear the gas block on the intermediate (11.5" from receiver). The M203 hangers are just at the rear of the gas block.
You will have plenty of room with the shorter mid-length gas system (about 9") if you leave the hangers installed, but I see no reason to leave them installed. Unless you have a M203 of course....Something else to become loose.
Intermediate is not the same as mid-length.
That being said, the M203 hangers have to be removed to clear the gas block on the intermediate (11.5" from receiver). The M203 hangers are just at the rear of the gas block.
You will have plenty of room with the shorter mid-length gas system (about 9") if you leave the hangers installed, but I see no reason to leave them installed. Unless you have a M203 of course....Something else to become loose.
Just coming across this and a little late I guess, but I just installed a RIS II on my mid length gas system. I used my fsb shaved down for the gas block and I had to remove the M203 hangers because they just touched the front of the gas block. I think if I'd gone with a smaller low profile gas block they would have fit with a little room to spare though. Just an FYI for anyone else reading this.
jonconsiglio
07-26-11, 13:44
Glad you brought this back to life as I'm seriously considering replacing the URX II on my SR15 with the M4A1 RIS II after getting a mk18 RIS II.
I reall like the RIS II over just about every other rail on the market.
Noveske barrels, Vltor upper receivers and DD rails...a few of my favorite things...
It's amazing how accuratley the DD RIS-II mates up with a Vltor MUR. Just shows how dimensionally perfect both are.
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