18" AR's

RugershooterRugershooter New MemberPosts: 8 New Member
Anyone on here have any firsthand experience with an 18" barreled AR? Specifically and 18" running a mid length gas system? I've mentioned that OBR lite on here a few times and would like to know what others have to say about such a setup.

Replies

  • breamfisherbreamfisher Senior Member Posts: 13,176 Senior Member
    I have a midlength gas system on my 16" AR. What sort of questions do you have? Some might be able to answer them. If you're wondering about reliability or functioning of the OBR Lite platform, it's a LaRue. They have a top-notch reputation.
    Overkill is underrated.
  • alphasigmookiealphasigmookie Senior Member Posts: 8,775 Senior Member
    I've got a stag 3g upper that's 18" but I'm pretty sure it's got a rifle length gas system.
    "Finding out that you have run out of toilet paper is a good example of lack of preparation, buying 10 years worth is silly"
    -DoctorWho
  • RugershooterRugershooter New Member Posts: 8 New Member
    I'm a little concerned about the mid lenght system on the 18" barrel. I had a Stag m3 with the carbine lenght system that I felt was very over gassed. I've done a lot of reasearch on the gas systems v barrel lengths and I dont want to have the same situation where the rifle is beating itself up because LaRue does use the middy on both 16 and 18". I'm curious does anybody know if the size of the gas port on the barrel or the block itself is designed to account for the longer dwell time of the 18"? If not i'm strongly considering switching to the 16". I realize this may be a frivilous concern but this is my first time buying a high dollar rifle and I want to do it right. I appreciate your patients.
  • shotgunshooter3shotgunshooter3 Senior Member Posts: 5,425 Senior Member
    I don't understand why we need the mid-length system personally. Seems like rifle length works just fine.
    - I am a rifleman with a poorly chosen screen name. -
    "It's far easier to start out learning to be precise and then speeding up, than it is having never "mastered" the weapon, and trying to be precise." - Dan C
  • breamfisherbreamfisher Senior Member Posts: 13,176 Senior Member
    I don't understand why we need the mid-length system personally. Seems like rifle length works just fine.
    It's mainly for carbine-length barrels. The carbine-length system was developed originally for the 10" and 11" barrels of the original CAR-15 rifles. It works fine in those barrel lengths, and is slightly overgassed in the 14.5" barrelled M4 and M4geries. It really gets overgassed on the 16" carbines, as you've added 5" to 6" more barrel and that increases the dwell time (amount of time the bullet is in the barrel after it passes the port), leading to more gas getting into the action that come in hotter, with a more violent action. This leads to premature wear of parts, gas port erosion, and more fouling. The mid-length system, with a 16" barrel, reduces that.

    The problem with going to a rifle-length system in a 16" barrel is that there might not be enough dwell time to allow sufficient gas to get into the gas system, leading to undergassing the system.

    Edited to add: now, the Mk 12 Special Purpose Rifle used by the US Navy seems to use an 18" barrel with a rifle-length gas system. Given its users, I'd say it's pretty reliable.
    Overkill is underrated.
  • Gene LGene L Senior Member Posts: 10,313 Senior Member
    And a Douglas SS barrel, a tie in to another thread.
    Not too many problems you can't fix
    With a 1911 and a 30-06
  • LerchessLerchess Senior Member Posts: 550 Senior Member

    The problem with going to a rifle-length system in a 16" barrel is that there might not be enough dwell time to allow sufficient gas to get into the gas system, leading to undergassing the system.

    Edited to add: now, the Mk 12 Special Purpose Rifle used by the US Navy seems to use an 18" barrel with a rifle-length gas system. Given its users, I'd say it's pretty reliable.

    A few companies are making Dissipator rifles which are a rifle length 16". I haven't heard any feedback from anyone who has one though.

    I can verify the MK12 - it is rifle length and it is smooth and reliable. I got one of Monty's uppers a couple of years ago.
Sign In or Register to comment.
Magazine Cover

GET THE MAGAZINE Subscribe & Save

Temporary Price Reduction

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Get the top Guns & Ammo stories delivered right to your inbox every week.