LMT MWS Suppressed Over-Gassed Fix? Part 1

Saf3sh00t3r

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  • Feb 10, 2017
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    San Antonio, TX
    Recently while looking for a new SR25/DPMS pattern AR type rifle that would be caliber adaptable, so I opted for the LMT MWS .308. My goal ultimately was to run it suppressed and unfortunately the gun did not have an adjustable gas block, let alone an adjustable gas key…all this I already knew when purchasing it and this sent me on a quest to address the BCG speed and over-gassed issue causing stovepipes when suppressed, but the best thing about my choice was that I could change my barrel with little or no effort and to a totally different round option. I also found it to be a ¼ to ½ MOA rifle @ 100 yards with an SS 20” barrel.

    The gun as of today has received basic improvements to address the BCG speed due to being over-gassed and it’s a better gun to shoot all the way around suppressed and unsuppressed.

    Anyway, here is the rifle so far and below is the story as well as how I got things to work out well.

    IMG_3118_zpskleoqmuq.jpg

    Here is the story:
    In order to address the lack of being able to adjust gas left me with two options 1) replace the gas-key on the BCG to an adjustable or 2) change the bolt carrier to my only option Gem-Tech’s adjustable gas carrier.
    I chose the carrier vs. monkeying around with my existing BCG’s gas key. The Gem-Tech carrier also is very easy to adjust compared to an adjustable gas key that usually requires an allen tool.

    IMG_3109_zpswqprj34b.jpg



    IMG_3106_zpsdajjc3jf.jpg


    The challenge was the BCG component combination, which is when the quest began. The LMT bolt and firing pin worked “ok” on the new BC, the problem was when the bolt release on the lower was pressed the round was picked up and BANG! The round would go off due to being too far forward. The firing pin was protruding a little too much and was not floating very well. This happened primarily when using a leitner-wise retaining pin more so than others. Since this was unsafe, it needed to be fixed.

    Basically the firing pin retaining pin and firing pin were incompatible with the new carrier. The retaining pin kept the firing pin more forward than normal and when the bolt would go into battery a primer strike would happen because the firing pin was not floating well. I found this was because in the LMT firing pin is shorter and the Leitner-Wise retaining pin diameter was larger and different when compared to the LMT captive retaining pin. I tried different retaining pins, such as DPMS, Larue(cotter pin), etc. the item I noticed was the firing pin was still shorter. I obtained a few new firing pins from DPMS, Larue, Knights, etc…the issue with those was the diameter of the pin at the bolt face…which was .080” or so and the LMT bolt is .068”.

    The next option was to use a completely different bolt altogether, so I chose JP Enterprises High Pressure Bolt because it uses a .062” firing pin at the bolt face that would be perfect for the 6.5 CM round as well as the .308 win. The LMT uses .068”, so I figured this would be the best option. See below the differences in firing pin size.

    IMG_3097_zpsmmkwg2o8.jpg


    After checking headspace, I headed to the range and with much surprise the new Bolt and Carrier combination worked quite well. At some point, prior to these upgrades, I had added a heavier buffer and new spring because of the new PRS stock. Here is my target @ 100 yards using Federal GMM 168 grain, which this rifle likes the best so far. The point of impact shift was minimal at about 1 inch, the group below was after re-zero with the Silenceco Harvester Big Bore using an ASR Break and mount.

    IMG_3119_zps1vhrxspj.jpg


    That said, this thing has now a Gem-Tech Carrier, JP Enterprises HP Bolt, and Slash’s Heavy Buffer with rifle spring. I figured this combination would help someone else’s LMT MWS .308 saga.

     
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    Reactions: smg1231
    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/03/2016 Last edited 01/03/2016 by deafsmith

    How much of a variable did barrel length play?



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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/03/2016
    (1 vote)

    The rifle has a 20 inch barrel stainless steel primarily. Shot with both the 16 inch barrel and a 20 inch barrel, both caused issues shooting suppressed. Meaning that the LMT BCG speed was a challenge. Now with the updates described on this post, the cases eject about 3 to 4 o'clock vs 1 o'clock with little recoil. Was out today and I shot to 700 yards hitting 7 inch steel plates consistently. Suppressed muzzle velocity was 2660 ft/s using 168 grain Fed GMM.

    Also gas to the face was minimal. I assume because it's a harvester big bore and barrel length. I'm a novice so that's just my guess.
    galaxyknucklesXSergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/05/2016

    cool, good info, when I first mounted a can on my 16 inch, bolt speed was a major issue when using the JP silent capture spring, in short couldn't get a combo to work reliably with a can, went back to the original buffer and it works reliably, but I do feel the gun is recoiling more, but reliably.

    when I tried the JP silent capture solution, the gemtech carrier was just coming on the market, so I may have to give that a try, would also like to revist the JP silent capture spring with this combo,

    How is reliability shooting the MWS in the suppressed setting without a can mounted? I know LMT likes to run redline for reliability so I think that this combo could dramatically improve recoil impulse?
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    wjm308
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/05/2016

    I had similar issues with my LMT MWS when suppressed, but never tried the BC with adjustable gas key, certainly looks like it works for you! I got so frustrated with my LMT that I sold the rifle to a friend who didn't intend to shoot it suppressed and then proceeded to build my own, while my new build shoots much smoother suppressed than the LMT, I have been unable to get my new rifle to group better than 1.5MOA and my expectation was better than 1MOA. Seeing your groups make me cringe at selling the rifle. Is that group 3 rounds or 5 rounds, it looks to be 5 but just want to make sure.

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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/06/2016 Last edited 01/06/2016 by saf3sh00t3r

    Hey Galaxy...if you use the Gem-Tech BCG in without a can and suppressed setting, you will only get 1 round out after releasing the bolt catch, but does eject the spent case. You will have to pull the charging handle for another round.

    I have an LWRC REPR and a SIG DMR 716 that when the suppressed setting is on, they do the same thing, 1 round at a time, so the BCG doesn't go far enough to pick up a round, but does eject the spent case. Just not enough gas to work the BCG and pick up a round from the mag.

    The rifle without a can and the "unsuppressed" setting on the GenTech BCG is very good, no issues FTF, stuck cases, etc.. It is very little felt recoil as well, much less than when I use the factory LMT BCG. It may be because as I mentioned in the original post I have a slash heavy buffer with rifle spring along as well.

    Don't know if you're aware but you need to take the gem tech BCG out to change between suppressed and unsuppressed. Its very simple to do, you can do it with a spent round case if you have to.

    The best thing about this setup, is little recoil suppressed and unsuppressed. Little to no Gas to the Face when suppressed.
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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/06/2016 Last edited 01/06/2016 by saf3sh00t3r

    Bill, yes that is 5 shot group, the widest of the range session. This one is the second group I shot that day at a 100 yards for a total of 5 groups (25 rounds total) all were pretty similar in size. Honestly, it was my first time shooting the new setup and was concerned about mixing and matching parts, so my groups could have been better I think.
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    galaxyknucklesXSergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/06/2016

    hmmmm, good stuff, there are a number of ways to address the issue, it appears the gem tech BC is one of them,

    I wonder what its bolt speed is compared to the LMT?

    I am also thinking about having my 18 inch barrel cut back and rethreaded to 16 with rifle length gas system all KAC m110k1

    but I want to do some testing as my 18 inch SS barrel is new and I don't even have a load worked up yet,
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    wjm308
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/06/2016 Last edited 01/06/2016 by wjm308

    saf3sh00t3r wrote: Bill, yes that is 5 shot group, the widest of the range session. This one is the second group I shot that day at a 100 yards for a total of 5 groups (25 rounds total) all were pretty similar in size. Honestly, it was my first time shooting the new setup and was concerned about mixing and matching parts, so my groups could have been better I think.​
    That just makes me want to cry
    frown.gif
    By the way, your rifle looks great!

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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/06/2016

    Bill...I am sorry man, when researching the combination and issue, I came up with saw your posts and rifle.

    Tons of posts, but It seemed as if no one had an answer for the issues we were having. So I began trial and error, it was a pain in the butt to be honest which is why I decided share it on the forum.

    Thanks for your kind comments about my rifle.
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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/06/2016 Last edited 01/07/2016 by saf3sh00t3r

    Galaxy... I can tell you that with the factory buffer and spring as well as BCG from LMT. The ejection pattern was 2 o'clock as brass was ejected without a suppressor. Suppressed, it caused a ton of issues and ejection was closer to 1-1:30 o'clock.

    The heavy buffer moved the pattern to 2:30 o'clock at best, making it better in terms of slowing down the carrier and making it more reliable in feeding new rounds.

    The Gem-Tech and Heavy Buffer, cleaned it up completely. So, you won't go wrong with at least a carrier upgrade if you plan to suppress. I used the BCG upgrade with LMT factory Buffer and it worked very well, but the heavy buffer is just a nice add to further reduce recoil.

    I think with your rifle, the only thing you will get is less muzzle velocity not much else from 18" to 16". 18" is a good length for .308.

    Anyway...Gem-Tech ran this test using a high speed camera to figure out the benefits of the carrier. It may help answer some of your questions.

    http://www.gem-tech.com/store/pc/pdf/BoltAnalysis.pdf
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    nedceifusXSergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/08/2016

    Thanks for posting up this info!!!
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    SNIPERS4DUMMIESXFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/09/2016

    Great post and thanks for the heads up, I was going to run the factory LMT bolt on the Gemtech Carrier.
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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/10/2016

    SNIPERS4DUMMIES wrote:

    Great post and thanks for the heads up, I was going to run the factory LMT bolt on the Gemtech Carrier.​
    No problem, if you have any questions let me know. I tried a ton of things with no success. One thing to note, the JP bolt uses rings that will make the bolt appear loose in terms being "worn-like" as it moves in the Gem-Tech carrier. The test of standing the carrier on the bolt will not work. This is normal for the JP bolt. I verified with JP tech support, those guys know their stuff. It seems odd, but on my rifle it works just fine. Used reloaded ammo today with no issues at all as well.

    Will continue to provide updates on this forum post.

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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    01/24/2016

    Update: After about 200 rounds shooting suppressed I started having some issues with the bolt going into battery on the first round from a newly loaded mag as I push the bolt catch release. At times I've had to pull/release the charging handle, then all is fine. Once the bcg is cleaned the problem goes away, the problem returns at about 200 hundred rounds. Again this only happens when loading the first round of a mag if the bcg is dirty and somewhat dry from suppressed shooting.

    No issues like this at all shooting unsuppressed. At least I have not experienced it after 440 rounds without cleaning in between.
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    nedceifusXSergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    02/01/2016

    Have you had a chance to get any more rounds threw this gun since your last post? A good running MWS suppressed is kind of a unicorn & I am intrigued.
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    saf3sh00t3r
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    XFirst Sergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    02/01/2016 Last edited 02/01/2016 by saf3sh00t3r

    nedceifus wrote: Have you had a chance to get any more rounds threw this gun since your last post? A good running MWS suppressed is kind of a unicorn & I am intrigued.​
    Hey Ned, yes I have...The gun in this config works so far with no cycling issues or anymore problems going into battery as reported earlier due to being dirty...have switched to Slip2000 EWL from CorrosionX oil, which seems to have addressed the problem...This MWS pink unicorn seems to be so far so good and actually flying on top of a dragon over a rainbow.

    Just as follow up, when the issue happened all I had to do is get that first round into battery the rest of the rounds in mag cycled fine suppressed.

    I went from having to do a simple wipe-down of the BCG and lubricating it every 200 rounds when shooting suppressed to now so far about 600 rounds suppressed without those issues, not going to clean it until they reappear so I can get a count or accuracy sucks. I also assume the gun components are matting from a "wear" perspective, meaning they are breaking in. Never had the issues unsuppressed. Again, all that changed now is lubricant.

    Use hand loads and factory ammo with no issues. Primarily use GMM 168s and Sierra Hand loads using FC brass.

    Ive shot out 800 yards consistently. Just switched to Hornady 168 amax hand loads, haven't shot them yet, once I do then will report back.



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    galaxyknucklesXSergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    02/02/2016

    between the gas block being pressed on and the 45 degree gas port, a typical adjustable gas block is not an option
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    nedceifusXSergeant
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    Re: LMT MWS Suppressed Over-Gassed Fix?
    02/02/2016

    Thanks for the update, I really appreciate having some info to go off of rather than learning the hard (& expensive) way as usual.