Suppressed Grendel's

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  • wraith1516
    Warrior
    • Dec 2014
    • 316

    #31
    Very interesting vid

    Comment

    • LRRPF52
      Super Moderator
      • Sep 2014
      • 8569

      #32
      Originally posted by Klem View Post
      A bit of a generalisation there.

      Depending on the volume of the can, especially the first vessel or expansion chamber. The larger the expansion chamber the less back pressure there will be. An efficient suppressor will have a large enough expansion chamber to mitigate the gas produced by 28 grains of powder. Barrel length is important here as that is also an expansion chamber. Shorter barrels will have more muzzle pressure the can has to mitigate. If your can is big enough then it is better to choose a bore which is as close to your calibre as possible. Manufacturers typically allow for 0.5mm clearance between the bullet and the baffles (a 6.5mm bullet travelling through a 7.5mm hole).

      Over-barrel suppressors permit a decent expansion chamber whereas it's more difficult with muzzle forward. There will always be a degree of run-out the manufacturer has no control over that is introduced by the person who threaded the muzzle. The longer the suppressor forward of the muzzle the more exacerbated this run-out is, leading to bullet yaw, shift of POI and finally baffle strike. The longer the suppressor forward of the muzzle the 'heavier' the moment of weight will be from the balance point and also it just get ridiculously long. My point being, a decent expansion chamber is a luxury muzzle-forward suppressors don't have, especially when you also need length for enough baffles to peel/divert the gas.

      Volume, is of course length by diameter minus whatever baffles and internal support the manufacturer has inside. In AR's, if you are not using iron sights your suppressor can be as wide as they come. Standard wide for suppressors is 1.75" diameter but on an AR with a 2.5" bore height to scope you can go way more than that. The bore height on an AR is 2.5" so you can even put a 4" oil filter on the end and still have clearance for the scope's cross hair. Fatter cans means shorter suppressors, as long as there is enough length to effectively peel the gas following the bullet. Makes me wonder why manufacturers don't make dedicated fatter cans for scoped AR's. Most recent I heard was on this forum where a manufacturer is making an injection-moulded titanium suppressor dedicated for AR's Its 2" diameter is wider than the norm but is level with the upper rail, obviously to permit iron sights. I'm thinking something even wider, around the 3" diameter mark.

      The sound coming out of the receiver of a suppressed AR is not all gas system and BCG. It also comes out of the chamber. As you know the chamber is not hermetically sealed when in battery. The case expands, especially at the neck to seal so the case is doing half the work of containing the pressure. As the 'elastic' case starts to retract gas is forced around it and back out into the receiver. The bolt unlocks and you get spit and noise in the face (I'm a left-hander). I use suppressors on AR's both with and without pistons and even with pistons there is noise from the chamber and they spit in your face.

      How much sound you mitigate at the receiver by going a larger suppressor bore is an interesting question. By doing this you are mitigating sound at the receiver at the expense of sound at the muzzle. I don't have the answer here but with respect, I don't think 52' has the definitive answer either.
      Yes. It's why I used the word "guideline" and not "rule". Since most of the suppressors in the US are not reflex types, manufacturers are limited to what they can do with initial expansion chamber.

      When I was talking with engineers from Colt Canada at SHOT, one of them said they did high speed video comparison with the HK416 and regular C8s. His point was to illustrate that the Canadian units using cans didn't need the PRI Gas Buster Charge Handle, since the extra gas they were getting doesn't come from the charge handle, but from the chamber. Said you could see it clear as day on slow motion filming.

      I'm also a fan of more volume, but not at the expense of larger diameter or substantially increased weapon length. The Finns have a nice system for the Rk95, brake attack on a FAL-style muzzle device.
      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

      • Klem
        Chieftain
        • Aug 2013
        • 3507

        #33
        Originally posted by SDet View Post
        To answer the ultra question

        https://youtu.be/LJsG_NNOiTQ

        Interesting video...

        Here are his decibel readings in a spreadsheet. He fires five rounds each string and presumably we average the five for a more representative figure we can then use to compare.


        I did not hear a reading on two occasions so have left them blank.

        What can we conclude from all this? Arguably not a lot given the standard deviation of the strings and the few rounds fired.
        Trying to make sense of the different sides the meter was on and given it was not measured and placed at a specific location I don't think we can conclude much, except that there's not a big difference for either side. With the 9" can however there is, and perhaps that's because the longer suppressor being more efficient means the sound coming from the receiver is louder than the muzzle. Running with this theory I might also assume the 5" is less efficient than the 9" and that's why there is no difference in sound on either side of the gun. The meter is placed on the table is picking up the loudest sound being the muzzle, so that's why there appears to be no difference between left or right side. Certainly the 5" can is louder than the 7" and 9" cans, which is what you would expect.

        Interesting there is almost no difference in sound reduction between the 7" and 9" suppressors. Also that there was no difference between the two calibres across 30cal and 6.5 for both the 7" and 9". Meaning, a 7" 30cal can is just as quiet as a 9" 6.5mm can. There is a difference however between the calibres on the 5" can.

        Pity Ray did not fire a few control rounds with no suppressor on the gun. Regardless, it is good of him to have done this and I appreciate his efforts on what looks like a very cold day.
        Last edited by Klem; 02-21-2017, 06:31 PM.

        Comment

        • TKO
          Bloodstained
          • Feb 2017
          • 70

          #34
          If you scroll down to the comment section on the YouTube page you will see all shots listed:


          5" 30 Ejection Port - 140.5 , 142 , 138 , 142.5 , 139.5
          5" 6.5 Ejection Port 136 , 140 , 136 , 138 , 142

          7' 30 Ejection Port 135 , 139 , 136.5 , 138 , 139
          7' 6.5 Ejection Port 139.5 , 138.5 , 138 , 136.5 , 137

          9" 30 Ejection Port - 140 138 135 136 139
          9" 6.5 Ejection Port 137.5 138 137 137 140

          9” 6.5 Shooters Ear 130 130 133 133 129


          5" 30 Shooters Ear 140 145 142 140 143
          5" 6.5 Shooters Ear 139 140 142 141 141

          Changes your averages by less than 1 DB in the incomplete columns.
          Last edited by TKO; 02-21-2017, 11:33 AM.

          Comment

          • HONDO
            Bloodstained
            • Jan 2015
            • 34

            #35
            Very nice. This answers my question and is very informative. The 7" .30 cal is perfect for my needs. Now just need to jump through all the hoops...
            Galatians 2:20-21

            Comment

            • LRRPF52
              Super Moderator
              • Sep 2014
              • 8569

              #36
              On a bolt gun, you definitely hear the difference between the 5, 7, and 9 Ultras.

              Since the Ultra 5 barely feels like there is a can on the end of the gun, I think it makes a great suppressor for the AR15, especially one that will be used for hunting.
              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

              • Chrazy-Chris
                Warrior
                • Aug 2015
                • 169

                #37
                I'm definitely interested in these. The Ultra 5 looks AWESOME. Anyone with personal experience know if it makes the Grendel AR and/or a Creed Bolt Action tolerable without earpro? I have a Specwar762 but the thing is just plain too heavy for anything other than bench shooting.

                Also, what is the preference on direct-thread versus the quick attach brake? How do the threads hold up over time on both the barrel and the can?

                Comment

                • LRRPF52
                  Super Moderator
                  • Sep 2014
                  • 8569

                  #38
                  Ultra 5 is pretty quiet. For one or two shots, it isn't bad. I wouldn't wear ear pro hunting with it.

                  I prefer brake attach method. Too easy.
                  Last edited by LRRPF52; 05-17-2017, 09:10 PM.
                  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

                  • Bigs28
                    Chieftain
                    • Feb 2016
                    • 1786

                    #39
                    Direct thread is about an ounce ish liter. The website doesn't list the weight of the break but when I called last will they told me the weight of the break.

                    Comment

                    • isymfs
                      Unwashed
                      • Mar 2017
                      • 1

                      #40
                      Would a Omega 9K work on a 6.5 Grendel?

                      Comment

                      • Smoke
                        Unwashed
                        • Dec 2014
                        • 16

                        #41
                        Originally posted by LRRPF52 View Post
                        I don't recommend using a 6.5mm can on a gas gun, as while they are efficient at the muzzle, they push a lot of supersonic gas out of the vents in the bolt carrier.

                        Stick with a .30 cal can for 6.5mm gas guns is a good guideline to follow.
                        I would have to agree .. 30 cal cans on the 6.5 Grendel work great
                        I was here once .. Got killed by the site .. Back again but not much

                        Comment

                        • shooter545
                          Warrior
                          • Aug 2012
                          • 249

                          #42
                          I have a Surefire SOCOM 762 Mini and a SOCOM 6.8 RC. I have run them both on my 18" JP and the 20" AA. They both work great and I can't really tell a sound difference between them(full disclosure, I have some hearing loss in my right ear); the 762 Mini MAY be a tiny bit louder but that is all subjective. What I did notice is that the 762 Mini has less back pressure due to the larger bore.
                          I run a SOCOM 762-RC on my 20" .260 and runs nice. I am going to order a couple of the Thunderbeast Ti cans. Had a chance to shoot them and they are NICE! I really want to try the 6.5 Ultra 7 on my Grendels.

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