length between gas block and receiver on mid length system?

[Armed-RN]

I am building my first DPMS .308 and have one of the POF uppers with the 11" rail attached, that's 11" from the front of the receiver to the end of the rail.  I need to know what length of gas system I need so that the 11" rail will cover the gas block so I can order the barrel.

Thanks

[Jgun]

I don't know how the different barrel makers decide gas block locations, so this may not apply for other brand barrels. I have a Noveske 7.62 Afghan barrel on one of my guns. Noveske discribes this as a barrel with a carbine gas system. The distance from the font of the receiver to the back of the gas block is around 9.400" , which puts the front of the gas block at 10.400" assuming your using a 1" GB and not one of those long GB's. the 1" GB would be covered by a true 11" long rail with approx 1/2" to spare. The rifle length GB for the 7.62 is approx. 12.725" from the recceiver to the back of the GB so you'd need a 14" rail to cover that. I know that Armalite has a different length (by about .250") but I don't know of any other standard gas block locations in between those two, so I guess your looking at a carbine gas system if you want the GB covered by your 11" rail.

[Armed-RN]

That's the info I was looking for. Now I just have to find an 18" barrel with a carbine length gas system, or get one with a mid length gas system and use a flip up front sight gas block.

Thanks for the reply

[Jgun]

Just for my information, If 9.4" is cabine on a 7.62 gun anf 12.750" is rifle length, what is the location of the back of the GB on a mid length gas system?

[98Z5V]

The 14.5" Noveske Afghan barrel has a mid-length gas system - you sure on yours, Jgun?  A mid-length gas tube is 9.5" long.  Just sayin'...

[Jgun]

here's where things always get confusing to me. The way it was explained to me when I first started building .308 instead of 5.56, was that 5.56 mid length was considered 7.62 carbine. The reason that I describe the Noveske 7.62 cal 14.5 " Afghan barrel as carbine length is because that is what they call it on their website. I also have a 5.56 cal 14.5" Noveske Afghan barrel on another gun and as far as I know Noveske describes that as a mid length gas system (7.5" being 5.56 carbine length) That was why I was saying that I was unaware of a mid length gas setup for 7.62. If I go by their specs and call 9.4" carbine length for the 7.62 then a 5.56 carbine gb location would have to be considered Pistol or SBR for the 7.62 cal.  Obviously what really matters is getting it straight with your barrel maker (if having a custom barrel made) so he puts the port and GB mounting dia in the right place for you. I always wonder about whether you could cut down/modify the gas tube to locate it where you wanted, because that seems to be the thing that limits us as to where we can locate them, (fitting one of the standard gas tube lengths).

[toshu]

The DPMS 7.62 SASS barrel is identified as having a mid length gas tube, but no dimensions are given

http://www.dpmsinc.com/store/products/?prod=4865&cat=1763

[98Z5V]

It's gonna be a standard AR-15 midlength gas tube (approx. 9.5").  If Noveske is really doing this, then they're the only ones doing it.  Noveske is also primarily Armalite components, and Armalite gas systems are slightly different from "the norm" anyway.

Don't get wrapped around the axle over this gas tube/gas system stuff, guys.

[Jgun]

It's just another example of why building the .308 AR's is so much more "interesting" than building the 5.56 guns because of there being no industry standard for them.

[Jgun]

this is the barrel on my 7.62 Mega. As you can see it's described as 7.62 carbine gas system, but I can assure you the gas block is located where I said.

              noveskerifleworks.com/cgi-bin/imcart/display.cgi?item_id=b-145-762&cat=160&page=1&search=&since=&status=

and this is the 5.56 Afghan barrel. as you can see it's described as being mid

length.

        noveskerifleworks.com/cgi-bin/imcart/display.cgi?item_id=b-145-556&cat=158&page=1&search=&since=&status=

                 

[imschur]

I think we need a 98Z5V gas length system. It's 2'' shorter than a carbine but it's as fat as a Blunt

[98Z5V]

I think we need a 98Z5V gas length system. It's 2'' shorter than a carbine but it's as fat as a Blunt

And it can handle the pressure...  <lmao> <munch>  It's all in the girth, not the length...  <thumbsup>

[imschur]

And it can handle the pressure...  <lmao> <munch>  It's all in the girth, not the length...  <thumbsup>

308AR.com "Short stroking isnt always a bad thing"

[98Z5V]

Damn, I can't even come up with a smartassed reply to that...  :-[ <laughs>