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LR 308 Gas Tube vs AR 15 Gas Tube

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I've been searching around and can't seem to find an answer to my question, so here it is. I'm currently changing some things up with my factory DPMS LR 308 AP4, and decided to change the carbine barrel to a SASS barrel. Well, I need to upgrade my gas tube to mid length when I make the swap. My question is can I use a AR 15 mid lenght gas tube on my LR 308 with my new SASS barrel? I'm just not sure if there's a difference between the gas tubes on a 308 ar and a AR 15. Any help getting this sorted out would be greatful. Thanks in advance.

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  • 2 weeks later...

I remember when I was having a barrel done, being told that the Armalite, AR 10 gas block location differs from the Knights/DPMS by a small amount (around .250") so a gas tube for a rifle length gas system on a Factory built AR 10 would be a little longer (I think) than the rifle length for a DPMS. Now, since your not buying an Armalite manufactured barrel, just because Rainier sells this as being an Armalite pattern barrel, doesn't guarantee that they are going with Armalite GB location, it might just be that they are talking about it having an Armalite compatible barrel extension. Short version here is to call up Rainier and ask them, or just order the suitable gas tube from them along with the barrel.

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  • 2 years later...

I recently bought a DPMS LR308 with 20" barrel, cleaned oiled it up and took it to the range. It short cycled almost every shot. I took the upper off, pulled the bolt carrier out and looked at the gas tube and key. The gas tube looked to be about .25" shorter than the one in my AR15. When I got home I looked through my parts and found a old Armalite gas tube and installed it in the rifle. It looked to come back far enough into the gas key. A couple days later I went back to the range and it cycled perfectly. So even on a factory built DPMS I had to use a Armalite gas tube.

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