Fixed: 6.5G(18" MLGS Suppressed) stovepipe issues

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  • kansas
    Bloodstained
    • Nov 2017
    • 65

    Fixed: 6.5G(18" MLGS Suppressed) stovepipe issues

    I've had this Prairie Tactical Arms upper for about 18 months ... until about May 2017 ... no issues ... I have about 600rds thru this upper now .. 400rds has been Hornady 123 AMAX 100rds Hornady 123 ELD ... 80 rds has been 123 SST and 20rds Federal Premium 130 Berger. The stove pipes have happened only on the 123 AMAX and ELD (so far. Saturday, I cleaned the chamber and BCG and fired 35rds ... I use e-lander 17rd mags. I had 1 mag with 15rds and two mags with 10rds each. No issues. I did RTB and cleaned chamber and bolt again (also run 1 wet and 5 dry boresnakes thru the bore).

    Next day, 1 mag of 15 rds and 1 mag of 10yds ... 10 rd mag first had three stove pipes. This was with 123 AMAX.

    Came back cleaned again and tried 10rd mag of ELD ... got stove pipe on 2nd round.

    Called Dustin at PTA .. after a 30m discussion his theory is hornady soft brass, wants me to try ammo with different brass. I've had 100rds of Federal 130 berger on back order for a month ... website says "over due" ...

    ==
    So in my experience it could be

    01 - Dirty chamber
    02 - issue with extractor
    03 - issue with ejector
    04 - ammo
    05 - buffer assembly
    06 - gas port tuning

    So need to rule these out ..

    About a month ago I disassembled the bolt .. there was a little build up in the extractor, but no brass flakes. Also removed the ejector and replaced the spring and the roll pin. The roll pin looked a little mangled, but there were no brass flakes or any other foreign material in the ejector port.

    My cleaning regime is:

    Nylon chamber brush on 2 sections of cleaning rod in drill ... with CLP run it for 20 seconds in the chamber ... the swab out with patches. Then repeat.

    field strip BCG and clean with CLP, I also use brushes and dental pics and pipe cleaners ...

    pretty much how I was shown to do it in the army except the drill and the nylon brushes ... we didn't have that sort of stuff for cleaning rifles in my day.

    Then 1 wet CLP boresnake and 5 dry.

    I also clean the lower and the suppressor threads and the exterior ... but not every time ... after each shoot I clean the bore and BCG of stoners ...

    ==
    I also tried a different lower when I fired the ELD Sunday.

    ==

    Dustin didn't think it could be the gas port tuning. When I bought it, I told him to remove the muzzle break and wrap it in electrical tape as I would be using direct threat suppressors. He did that and said removing the MB would cover the cost of adding an adjustable gas port and he would tune it for suppressor. I reminded him of that when we talked.

    I also mentioned the value screw looked pretty far out to me.

    He said he leaves them wide open.

    ==
    So in the vein of trying to rule out anything and everything, tonight I removed the forearm and then the value screw (1/16 SAE) and sprayed a little brake cleaner in there and blew it out with compressed air. Letting it dry some ... then will put the value screw back in ... and tighten it all the way. That should shut off the gas (I think). Then the gun should fire, but not cycle. Then I will back it off until it cycles. That's what I'm reading other folks do to tune the gas port, so I will try that next.

    ==

    Other thoughts or ideas welcome!

    And I notice this sub forum as a few other people having similar issues ... oh my !!! I will say I am not bothered by the issue, I enjoy solving gun issues and reading about stove pipes, I am realizing that for stoners this is one of the "exciting" issues to solve! Three years ago my Sig 762 was having stove pipes ... I took out the ejector and there were brass flakes in there and the forum I was on then said "You found your problem" ... but a few weeks later, I learned that was just the symptom. The real issue was insufficient frequency of cleaning the chamber. That's why I'm crazy about cleaning stoner chambers now. But that doesn't seem to be helping in the current case.
    Last edited by LRRPF52; 12-20-2017, 02:24 PM.
  • VASCAR2
    Chieftain
    • Mar 2011
    • 6218

    #2
    Sounds like insufficient gas. I think your wise to try adjusting the gas block so it locks open with the bolt catch after firing one round. The only other thing I’d check is the extractor and spring tension. Some people have found their rifle functions better without the O ring some report needing the O ring in conjunction with the extractor spring to obtain reliable function.

    Comment

    • kansas
      Bloodstained
      • Nov 2017
      • 65

      #3
      Ok, closed to port almost all the way ... and fired one round with the magazine in ... the bolt did go back but not all the way ... it stuck on the mag ...
      Then opened it two full turns.
      Fired 1 rd from the mag and bolt locked all the way to the rear.
      Fired 8 rounds from the mag quickly and no functioning issue.

      ==
      So Dustin's port strategy seems to be the opposite of the one I'm trying.
      He said he leaves the port wide open on purpose.
      I am trying to close it and then open it gradually until the gun starts to function. Thus using minimum gas to thru the port.

      ==
      I can't say I am out of the woods yet ... I would like to see 200rds cycle with no issue before I declare victory ... but ready to get back to trying some more shooting and see what happens.

      ==
      Before I made this adjustment, I was stove piping with this ammo on the second round.

      Comment

      • VASCAR2
        Chieftain
        • Mar 2011
        • 6218

        #4
        The problem with gas operated rifles is the function is dependent on the amount of gas/pressure produced by the particular cartridge. The advantage of an adjustable gas block you can set your gas to work for different loads or for use with a suppressor. The 6.5 Grendel with 18” barrels with mid length gas systems can be finicky when using a suppressor hense the recommendation for an adjustable gas block.

        Running an AGB wide open with a suppressor can cause functioning problems because of to much gas. Sometimes it is hard to tell if a rifle is under gassed or over gassed as the symptons can be similar. Recent lots of the new Hornady ELD-M ammo are not producing as high of velocity as the earlier 123 grain factory A-Max. Newer ammo less velocity/pressure can affect functioning as well as change in temperature. You may need to open the gas block more in cold weather to achieve reliable function.

        Comment

        • kansas
          Bloodstained
          • Nov 2017
          • 65

          #5
          Great thanks!!! And by the way it was ELD I was using today for the test ...

          Well also, now that I've learned that my config is easy to take apart and adjust ... (can't actually adjust the gas block with the forearm on) ... I am ready to perform further adjustments as needed.

          The "split rail" (rear part for scope and forward part for clipons) ... means I'm not "bridging" the receiver to the forearm with either the scope or the rails ... so I can still take it apart. That wasn't my primary reason for doing the rails like this ... but it is a useful accident !!!

          Comment

          • VASCAR2
            Chieftain
            • Mar 2011
            • 6218

            #6
            If the adjustment screw is on the side could you drill a hole in the hand guard to get an allen wrench to the adjustment screw on your gas block. If the adjustment screw is on the front of the AGB I’d probably gerry rig an Allen wrench to an extension so I wouldn’t have to remove my hand guard every time I needed or wanted to adjust the gas flow.


            Glad your getting things sorted out, I like your color scheme.

            Comment

            • kansas
              Bloodstained
              • Nov 2017
              • 65

              #7
              Fired 52 rounds today at steel at 428 yds and 515 yds off tripod ... missed 9 ... the ELD 123 was hitting higher than the AMAX 123 and I didn't run a magneto speed on the ELD, so just had to make adjustments and aim down a little. I could see the dust of the misses.

              But that makes a total of 60 rds now fired since the gas block adjustment. The goal is 200 rds till we declare "victory".

              ==
              The adjustment screw is on the side and I could carve a little on one of the 45 degree angled holes and get access. But the hex wrench I need is 1/16 and it is THIN and I think I would not be able to turn it without bending it if I was sticking the long end in the hole and turning with the short end. So for now will continue to remove forearm to adjust. It is easy. Eight torx 20 screws out, then slide it off. To put back on, slide it on and 8 torx 20 screws in.

              It is a "liberating" feeling to have this gun shooting again without stove pipes

              ==
              Color scheme works around here for the cool half of the year ... green would be better for the warm half ... also my first Sig762 was tan, so I guess I was trying to match subsequent guns to the sig. The Sig is long gone, but the matching continues.

              Comment

              • kansas
                Bloodstained
                • Nov 2017
                • 65

                #8
                Ran 5 rds of ELD 123 across the magnetospeed v3.

                01 2428
                02 2418
                03 2432
                04 2428
                05 2426
                max 2432
                min 2418
                avg 2426
                SD 5.1

                Wow, I am impressed with the consistency !!! This is the lowest SD reading I've gotten so far for any ammo !!!

                (and btw we are now up to 65 rds fired after the gas block adjustment with no issue)

                Comment

                • kansas
                  Bloodstained
                  • Nov 2017
                  • 65

                  #9
                  Fired another 40rds without issue total 105 ... today it was all ELD 123. I spent 20rds zeroing the sh^t out of it ... I had set the zero stop at the zero for the amax123 and the eld was a mil higher at 100yds !
                  So I had to hold down a mil while zeroing ... have to zero off the tripod because the grass in the pasture is too high to see the targets if I lay down ... so I spent a few more rounds getting it done. Still good practice trying to hit a 3/4 inch orange dot at 100yds off the tripod.

                  ==
                  Then rolled to the 425 FP and setup the tripod. 10rds at 425 on the 12x24 steel silhouette ... the kestrel said 4.5 mph 315 degrees off the bullet path. That would've been .25 mil left ... but I am shooting over a creek and I know better ... so I held half a mil ... on elevation AB said up 2.8 but I cranked 1.8 since I was zeroed at 1 mil down.

                  miss - I could see the dust to the left a few inches, so I shifted to .25 mil I told tell the wind had died to almost nil around me ...
                  hit
                  miss - I could hear the wind picking up considerably, so held 1 mil
                  hit
                  hit
                  hit
                  miss - the wind blew me around and I missed to the right. increased hold to 1.2 with the increasing wind, est. to be spiking to 12 mph ...
                  hit
                  hit

                  ... everything made sense ... so rolled up the hill and stopped at a point I thought would be about 600yds ...

                  Three repetitions of the LRF said 580yds. The kestrel said 4.1 mph ... the AB said 4.8, so I cranked to 3.8. AB also said 1.3 for 10 mph, so I held 1 mil to start.

                  hit ... got lucky ...
                  miss .. to the right by inches ... held 1.25
                  hit ...
                  miss ... blew me around missed by inches to the right ... no change to the hold ...
                  miss ... same result ... hard to control the left to right wobble in the wind ... you really just have to time it right ...
                  hit ... it's a crap shoot, but sometimes you get lucky ...
                  miss ... not changing the hold, just getting blown around ...
                  hit
                  hit

                  These conditions are about the limit of what I can do with the tripod ... when the wind is blowing you around by a certain amount, it is a lot tougher ... I have been practicing the carabiner thingy on the belt loop with the sling through it and twisted around the tripod in the house ... but haven't used that in the field yet ... maybe it will help a little. So need to try that.

                  ==
                  But the gun is working ... so the evidence is accumulating that the gas port setting was the issue ... this is good news ...

                  Comment

                  • LRRPF52
                    Super Moderator
                    • Sep 2014
                    • 8569

                    #10
                    No secret to what was happening.

                    I would be more surprised if a MLGS 18" doesn't stovepipe when suppressed.

                    Cyclic rate goes way up when you suppress with most cans.

                    Looks like you got it figured out.
                    NRA Basic, Pistol, Rifle, Shotgun, RSO

                    CCW, CQM, DM, Long Range Rifle Instructor

                    6.5 Grendel Reloading Handbooks & chamber brushes can be found here:

                    www.AR15buildbox.com

                    Comment

                    • JJA Guns
                      Bloodstained
                      • Nov 2017
                      • 34

                      #11
                      Sounds like it was overgassed, and the bolt was cycling faster then the brass was clearing the ejection port.

                      Comment

                      • kansas
                        Bloodstained
                        • Nov 2017
                        • 65

                        #12
                        BTW, above I mentioned this upper worked fine for about a year, and then starting in May 2017 had issues. I've been trying to figure out "what happened" to change it. And the only thing I've come up with is the suppressor changed. I did have a SC Harvester on it. In May the Omega came out of jail and went on the 6.5G(18) in place of the Harvestor. So right now, my theory is the Omega made a difference.

                        The issue still seems to be fixed by adjusting the gas block, but the Omega may have been the cause of the behavior change in May.

                        Comment

                        • LRRPF52
                          Super Moderator
                          • Sep 2014
                          • 8569

                          #13
                          Originally posted by kansas View Post
                          BTW, above I mentioned this upper worked fine for about a year, and then starting in May 2017 had issues. I've been trying to figure out "what happened" to change it. And the only thing I've come up with is the suppressor changed. I did have a SC Harvester on it. In May the Omega came out of jail and went on the 6.5G(18) in place of the Harvestor. So right now, my theory is the Omega made a difference.

                          The issue still seems to be fixed by adjusting the gas block, but the Omega may have been the cause of the behavior change in May.
                          Increased back pressure, resulting in stovepipe malfs.

                          I'm going to update your thread title for the benefit of others that may be having the same problem running 18" MLGS suppressed.
                          NRA Basic, Pistol, Rifle, Shotgun, RSO

                          CCW, CQM, DM, Long Range Rifle Instructor

                          6.5 Grendel Reloading Handbooks & chamber brushes can be found here:

                          www.AR15buildbox.com

                          Comment

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