LMT MRP (non-CQB) upper and different length gas systems

[Spot]

I am very interested in buying a certain LMT rifle I've seen which has the longer MRP upper receiver with 15 handguard holes rather than the CQB MRP version which has 10 holes. It currently has an 18" SS 6.8mm barrel, but I would want to change it over to an 18" 5.56mm. I have read that longer gas systems than carbine-length are desirable for several reasons (which I don't fully understand). As I understand it, there are carbine-length gas systems, mid-length gas systems, and there are rifle-length gas systems.

What are my choices, and what are the pros and cons? I have heard that a mid-length gas system performs better than a carbine-length system. . . so does that mean that a rifle-length gas system will be even better than a mid-length system? What would the most appropriate gas system length be for an LMT longer MRP upper (non CQB) witn an 18" barrel, and why do you think so? Who's barrel would you recommend?

[strambo]

Well...a short quick answer is if you stick with LMT made MRP barrels, there is no choice for you to make. The 14.5" barrels are carbine gas, the 16" and 18" ones are mid-length.

You can also buy any barrel you want, then send it to a company to have modified for an additional $150 plus shipping to fit the MRP.

The mid-length 18" ss 5.56 barrels from LMT have a good reputation for accuracy and mid-length is a solid gas system for them. Rifle length would be softer shooting and less pressure, but could have reliability issues w/ weaker ammo.

I'm sure you would be happy with a rifle length MRP upper and the 18" ss 5.56 barrel.

[ALCOAR]

Strambo already answered nicely, nothing really to add other than no LMT MRP factory barrel option comes in rifle length gas for 5.56.

10.5" CL, 14.5" CL, 16" CL.....carbine length gas

16" CL, 16" SS, 18" SS.....mid length gas

Two different MRP chassis...CQB length and the Rifle length(one your referring to I believe.)

Here is a MRP rifle length chassis and MRP factory 18" SS 5.56 barrel...

http://i888.photobucket.com/albums/ac81/trident1982/DSC01388-1.jpg

[Spot]

Okay, it's really good to know that the 18" LMT SS barrel will automatically be a mid-length gas system (which I have heard is better performing). So, as long as it's an LMT SS 18" barrel, it will be the right match for the rifle.

Okay then, next question: I realize that I will need to change the bolt, the barrel, and the magazines to run it as a 5.56mm. Anything else that will need to be changed (or that should be considered)?

[ICANHITHIMMAN]

Okay, it's really good to know that the 18" LMT SS barrel will automatically be a mid-length gas system (which I have heard is better performing). So, as long as it's an LMT SS 18" barrel, it will be the right match for the rifle.

Okay then, next question: I realize that I will need to change the bolt, the barrel, and the magazines to run it as a 5.56mm. Anything else that will need to be changed (or that should be considered)?

You will have to re zero:D
http://i302.photobucket.com/albums/nn119/ICANHITHIMMAN/0012.jpg
http://i302.photobucket.com/albums/nn119/ICANHITHIMMAN/004.jpg