DispositionMatrix

I have everything but the barrel. It's been many months, and the LM308B220 20" barrel still does not seem to be available anywhere. Nor is the LM308B218S 18" stainless barrel.

I understood what I posted. It's pretty straightforward.

And that table is wrong. Here is a revised table: Aero Precision Armalite Comparison Buffer tubes Springs Buffers

Comparison of the Armalite AR10REKIT01 and Aero Precision AR 308 M5 Carbine APRH100158C buffer tube kits: Aero Precision Armalite Comparison Buffer tubes Springs Buffers

Has a red hard plastic tip, but yes. From Overpricedbuffers.com.

I have a short one from Brownell's stamped "Heavybuffers.com" for which the following copy was posted: Allows for installation of standard ar15 carbine stock on .308 ARs AR-15 buffers are too long and restrict bolt movement on .308 ARs with AR-15 stocks Simple drop-in installation Modified AR-10 buffer spring is recommended for maximum reliability Reduces felt recoil Compatible with .308 ARs ranging from: Armalite, DPMS, Remington, Knight's, LMT, Larue, POF, Mega, Fulton, And CMMG 5.5 ounces 303 stainless steel w/ a tungsten anti-bounce counterweight

Buffer tube depth: 7.625" Buffer (H3) length: 3.250" It is not any longer than any of my AR15 buffers. I have a couple of short "CAR-10 308" heavy buffers that are the shorter design.

I read that one a while back. Thanks. I'm guessing the internal depth of the buffer tube is going to be 7-5/8" and the buffer length is going to be 3.250". Maybe the comparison pics I get will be helpful to the next poor sap.

Thanks. I will take comparison measurements of the various tubes and buffers I have. Regarding gas ports, given no Ballistic Advantage, Criterion, Fulton Armory, etc. barrels have been available to send out for modification, LMT's LM308B218S or LM308B220 might end up being in stock first, eliminating the guesswork on ports.

AR10REKIT01 finally arrived. Standard carbine-length buffer tube. Standard-length H3 buffer. Is the magic all in the spring?

The problem now is finding any 18" or 20" barrel worth converting. Out of stock.

I was thinking the duration of time the gas affects the round as it goes down the barrel would matter, but a longer barrel with equal gas length as a shorter barrel shows lower average pressure just prior the the egress of the round.

I have one of those AR10REKIT01 kits inbound from Armalite. Thanks for the link. Since D. Wilson has made it clear they don't do the 7.62/.308 conversion I need, I have contacted Nefarious Arms on the advice of someone in this other thread. On the subject of barrels and gasing in particular, am I likely to have better luck getting to a modicum of reliability with 18" or with 20", assuming rifle-length gas for each? Again, this is for use with the LMT FULL-AUTO .308 BCG LM308DA I already have on hand.

Yes, I did. D. Wilson will not do a conversion for the MRP-H MLOK 15.5 LM308BML4A monolithic upper, which is just the long version of the MRP-H MLOK 12.5 UPPER LM308BML1 upper that is used on what LMT used to call their .308 "MWS" series of rifles--now called the "MARS-H 7.62" series. The MRP-H QUAD 12.75 UPPER LM308B1 upper used on the L129A1 REFERENCE RIFLE LM308SSR has the same quick-change barrel mount. I did post in that other forum about it yesterday.

That would seem to be the case. I have it on good authority D. Wilson does not convert barrels for fitment with the LMT MWS (.308) upper. They do conversions for the MRP upper.

I was referring to the outer dimensions of the gas block and the unit physically fitting within the rail, which is 15.5" long. I already have matched the gas block inner diameters to the barrels in the table above.

Here is what I've gathered so far: Barrels with rifle gas length Brand L Description PN/SKU Twist Journal Material Contour MSRP Gas Block Gas Tube Ballistic Adv 18" .308 HEAVY PROFILE RIFLE LENGTH AR 308 BARREL, MODERN SERIES BABL308007M 1:10" .750 4150 CrMoV Chrome $240.00 Ballistic Adv 20" .308 HEAVY PROFILE RIFLE LENGTH AR 308 BARREL, MODERN SERIES BABL308006M 1:11" .750 4150 CrMoV Chrome $250.00 Criterion 18" DPMS PATTERN 308 HYBRID BARREL, RIFLE GAS, NITRIDE 1018S-HYR-N 1:10" .750 SS-416R Nitride $359.99 Badger Ordnance TDX Gas Manifold 0.750″ Stainless Steel BCM Gas Tube Criterion 20" DPMS PATTERN 308 HYBRID BARREL, RIFLE GAS, NITRIDE 1020S-HYR-N 1:11" .750 SS-416R Nitride $359.99 Criterion 18" DPMS PATTERN 308 HYBRID BARREL, RIFLE GAS, CHROME 10180-HYR 1:10" .750 4150 CrMoV Chrome $359.99 Criterion 20" DPMS PATTERN 308 HYBRID BARREL, RIFLE GAS, CHROME 10200-HYR 1:11" .750 4150 CrMoV Chrome $359.99 Criterion 18" DPMS PATTERN 308 HYBRID BARREL, RIFLE GAS, STAINLESS 1018S-HYR 1:10" .750 SS-416R Stainless $339.99 Criterion 20" DPMS PATTERN 308 HYBRID BARREL, RIFLE GAS, STAINLESS 1020S-HYR 1:11" .750 SS-416R Stainless $339.99 Fulton Armory 18.5" .308 AR, Medium Weight, 1x10, Stainless, Match Quality, FA by Criterion FA-TU-003 1:10" .936 410 Stainless M110 $374.95 Gas Block, Adjustable, Low Profile, .936, Clamp On, SLR Sentry Fulton Armory 20" Barrel, 20", .308 AR, M110, 1x10, Stainless, Match Quality, FA by Criterion FA-TU-005-TM-SS 1:10" .875 410 Stainless M110 $369.95 Gas Block, Adjustable, Low Profile, .875, Clamp On, SLR Sentry Fulton Armory 20" .308 AR, M110, 1x10, Stainless, Threaded, Match Quality, Krieger FA-TU-007-SS 1:10" .875 410 Stainless M110 $634.95 Gas Block, Adjustable, Low Profile, .875, Clamp On, SLR Sentry Not sure about the gas blocks for the Fulton Armory barrels fitting in the MRP-H MLOK 15.5 LM308BML4A rail.

I read https://308ar.com/ar-10-308-ar-compatibility-reference-guide/ and https://308ar.com/ar-10-barrel-extension-ar308-barrel-extension/, but I am still unclear on which barrel extensions are common to which manufacturers and bolts. I need to match my LMT MRP-H MLOK 15.5 LM308BML4A monolithic upper and LMT .308 BCG (LM308DA). On Criterion's site, I am still trying to decode "DPMS PATTERN 308 HYBRID BARREL." Also, what is ".308 hybrid" in reference to barrels?

I appreciate the link. By "will work" do you mean it will work, will most likely work, or will put me on the correct path to working? Also, from a technical standpoint, what specifically makes the AR10REKIT01 kit correct/superior for, say, the mass of my full auto .308 BCG (LM308DA), assuming the gassing (ultimately) is correct? Is it the length of the tube, the spring, or the buffer size and weight? Is the tube, +3/4" like the .308 EXTENSION TUBE LMP259C or standard length? I noticed it's advertised as 6-position and not 7, like the LMT .308 EXTENSION TUBE LMP259C Is the included buffer spring a unique rate/stiffer/weaker/progressive? Is the buffer standard AR15-length or shorter? Is it 5.4oz or some other value? Additionally, am I to understand that the the Armalite AR-10® 6 POSITION RECEIVER EXTENSION KIT (NO STOCK) you are recommending is a better choice for this LMT .308 build than the LMT MWS BUFFER TUBE KIT LM308BTK included in LMT's premanufactured rifles? I am not questioning your expertise but am curious about the details. I may pull the trigger on the Armalite AR-10® 6 POSITION RECEIVER EXTENSION KIT (NO STOCK) to start the >3 month wait. Of the 3 barrel brands you mentioned, there is not much out there in rifle-length gas, which I gather is what I need, based on earlier reading, for an 18" or 20" barrel. I would also be curious as to whether low-profile gas blocks are available for them that actually would fit under the MRP-H MLOK 15.5 LM308BML4A rail. Based on this section of my build doc, I suspect I need to somewhat match these twist rates if sourcing a Ballistic Advantage, Criterion, or Fulton Armory barrel: LMT 20″ 7.62 NATO LM308B220 20" chrome-lined DI 1:10" LMT 20″ 7.62 NATO LM308B220S 20" stainless DI 1:11.25" LMT 18″ 7.62 NATO LM308B218S 18" stainless DI 1:11.25" I really appreciate the feedback.

Thanks. That's a lot to digest, and now I'm trying to see how that comports with the relevant pricey LMT parts I've already acquired, such as the full auto .308 BCG (LM308DA).

I found this forum after reading this post in /r/AR10 on Reddit within the LMT MWS Compatibility thread: If you're new, I would HIGHLY recommend learning the difference between an AR 10 and a AR 308 ( LR 308, SR 25, etc.) But I have been reading here prior to joining. I have also read this guide: https://308ar.com/ar-10-308-ar-compatibility-reference-guide I am doing a build, covered here: https://forum.308ar.com/topic/21203-lmt-mws-assembly/

Non-purist content warning. I am in the process of assembling an LMT MWS hybrid between what is now marketed as a "MARS-H 7.62 (MLKMWS-MARS)" and a "MARS-H 7.62 DMR (MLKMWSK-MARS)" in that I want an 18" or 20" DI barrel but with the longer MRP-H MLOK 15.5 LM308BML4A monolithic upper. (The low-profile gas block fits under the rail.) Lower is a MARS-HS. At this point, theoretically I have everything needed to get to the range except for a barrel. I realize building from LMT parts gets me around a lot of the knowledge that normally would be required to build an AR-10. Sights are Troy Micro MR556A1-style. The LMT components were more than expensive. Admittedly, I did cheap out on some of the back end lower components--generic A2 grip, AERO PRECISION - AR .308 M5 CARBINE BUFFER TUBE KIT*, and B5 SOPMOD stock from Brownell's in place of a currently-unavailable $300 .308 DMR BUTTSTOCK DMR308 from LMT. I went with a Geissele G2S trigger because it was available and cheaper than all the other triggers. *I am notably less solid on the buffer tube, spring, and buffer. Based on LMT's marketing material, I might instead want the .308 EXTENSION TUBE LMP259C (out of stock everywhere) to give me an extra 3/4" of length, which allegedly would allow for a standard AR15-style H3 buffer. Otherwise, it would appear I could use the Aero Precision milspec tube I bought along with the short, LR-308-style H3 buffer that came with it. At this point I have accumulated an assortment of LR-308-style (short) and AR-10-style (dimensionally equivalent to AR-15) H and H3 buffers. To simplify things, LMT does manufacture a MWS BUFFER TUBE KIT LM308BTK that appears to come with an AR-10-style (dimensionally equivalent to AR-15) H3 buffer, which _suggests_ it uses the .308 EXTENSION TUBE LMP259C. I'm even shakier on sourcing recoil springs separately, but have assumed the Aero Precision spring included with the kit I bought has the _correct_ spring for the included buffer. I'm open to suggestions.