Does anyone have an accurate measurement of an intermediate gas tube length? Would be nice to 3 decimal places. i.e. 13.625"
Thanks
Measuring mine on my rifle, a rough measurement puts it between 13 5/8" and 13 3/4". So somewhere between 13.625" & 13.75".
I’ll see if I can find something tomorrow to get an exact measurement. On a folding ruler, it’s close to 13 5/8" and the difference between that and a rifle length looks very close to 1 1/2".
1.5" shorter than the rifle
Someone please correct me if I am wrong. Noveske has an intermediate gas tube and so does KAC. Both are slightly different as I recall. So which one are we referring to? I think I remember seeing the number 13.16" somewhere.
I was looking at my notes and saw reference to the Noveske as being 13 9/16 inches.
Looks like the KAC is about .4" shorter than the Noveske gas tube.
I have a Noveske intermediate gas tube sitting in front of me on my desk, and it’s just a hair shy of 13 11/16"
The KAC gas tube is their SR25 gas tube. Not sure about the length though.
It’s the older SR 25 length, they don’t use them any more on any commercial gun I’ve seen in the SR 25 line in years.
Maybe this will help - I am trying to put together a rudimentary blue print for basically 5 standard bbl lengths; 14.5", 16.25", 18" Mk12 w/ rifle length gas systems, 18" Mk12 w/ “intermediate” length gas systems and the standard 20". I wanted to stick this on the wall next to the lathe for quick reference when doing bbl work.
Some of the lengths are derived via extrapolation. The 1.5" shorter than a rifle system indicates a 13.625" gas tube.
So, to be perfectly clear about my own lack of information - I don’t know what would be correct on and 18" bbl with an intermediate gas system - a Noveske or a KAC or…more to the point, if they vary, how does that difference effect the port location on the bbl? What was changed?
Looking for some hard data -
I can post the drawing if folks would like to comment or add data. Some of it was derived from actual prints, other from physical measurement and some from extrapolation. Let me know and I can post the drawing.
Hope that helps.
Yes, that helps.
The critical dimension is NOT the gas tube length, but the distance on the barrel between the torque shoulder (at the extension) and the gas block shoulder.
Everything else stays the same.
An 18" 5.56 barrel can work with MID, INT and RIFLE length gas systems.
Given that, either of the INTs will work, it’s just a matter of sourcing the proper tube.
I’d stick with the Noveske Length (rifle - 1.5") because it is a known quantity and finding gas tubes is likely to be easier.
ETA
From memory, the shoulder-shoulder distances are:
CAR 6.75"
MID 8.75"
INT 10.625"
RIFLE 12.125"
Clint,
Roger - I’m tracking on the gas tube length not driving the other dimensions - but rather the gas tube length as a result of where the gas port is because of different barrel lengths.
One dimension that appears to be constant is the CL of the gas port is .295" forward of the shoulder for the gas block/FSB.
Another interesting dimension is that when any bbl is measured from the bolt face to the CL of the gas port, that dimension is always 1.955 shorter that the corresponding gas tube length.
I am assuming that KAC moved the shoulder back at the gas block area to account for the shorter tube? (and this is specific to ONLY KAC intermediates?)
I have attached the somewhat crude print for comment - open to all for thoughts or corrections.
Thanks in advance.
The gas tube protrudes past the bolt face into the upper so that it mates up properly with the gas key. It doesn’t look like you accounted for that extra length.
When I design a barrel, I usually use the 0.295 from shoulder to port center when using a long (~2.00) journal, as it will likely have an FSB and needs a 0.030 space between the FSB and the shoulder for the handguard cap - however, if I am designing a barrel with a ~1.00 journal… which will not hold a handguard cap, I usually eliminate that space and the center of the port hole is located 0.265 forward.
Yes.
Neal0124,
Yes - thanks - well aware of that!! The drawing isn’t to scale - just representations - the critical issue is the actual measurements.
I’ve been building / turning / chambering bbls for 25+ yrs - my request for info is geared to the intermediate systems - specifically the linear measurements of the step downs and the relationship to OEM 20" bbls I have in stock; carbine bbls, M-4 bbls and 20" bbls - along with the attendant gas tubes - I don’t have the the mid-length or intermediate length gas tubes to measure. I was able to find actual measurements of a mid-length tube, but nothing on the intermediate. In searching, I learned that the (if I am getting my facts correct) Noveske & KAC intermediate tubes are each different - hence my posts.
All very interesting and actually very cool as it opens up significant performance possibilities.
K.L.
Great stuff - thank you (& Clint).
The .030 / .265 vs .295 dimensions - salient to turning a new bbl. I will incorporate that into other drawings. When I repurpose a bbl - I am stuck with the .295 dimension. I have done other bbls - speccifically in AR10 platforms where I moved the gas port forward 4" and had to custom mfr a longer gas lube. In instances like that - i completely did away with the allowance for a H/G cap and moved the shoulder forward as well as sizing the length of the journal to match my gas block.
That relocation effort yielded stunning results in a 6mmx22-250 wildcat AR10.
The focal point of the OP is really in identifying dimensions that I must work around when I re-configure/contour a repurposed bbl.
Your input is very much appreciated.
Well gentlemen, What about the Ranier 18" SS barrel with an Intermediate length gas system.
https://www.rainierarms.com/?page=shop/detail&product_id=2910
My guess is that it uses the Noveske length tube @ 13.625" Based on what I am told / seen / researched, the KAC intermediate is unique to them and may not even be in use anymore.
The KAC tube is used on all SR15 rifles 14.5" or longer. It is the old SR25 length tube. Current SR25 rifles appear to be using a rifle length tube.
I have a question about your project. If you were designing a barrel around the Noveske intermediate length, where would you get the actual gas tube? Are they available for purchase?