First time working up a Grendel load

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts
  • acourvil
    Warrior
    • Dec 2013
    • 112

    First time working up a Grendel load

    I've reloaded for my bolt guns in the past (260 rem and 300 WM), but this is the first time working up a load for a gas gun. The gun has a 22" JP barrel, adjustable gas block.

    I'm starting with Lapua brass, 8208xbr and 123g Lapua Scenars, working in .3g increments up to a max of 28.4g. The BTO is 1.695, OAL of ~ 2.25.

    What, if anything, should I be doing different in evaluating a load for a gas gun? What I am wondering most about is pressure signs. Since the max pressure for the Grendel is so much lower than with one of my bolt guns, what should I be looking for?
  • JASmith
    Chieftain
    • Sep 2014
    • 1620

    #2
    Take a good look at Chapter IV "Detecting Abnormal Pressures" (pges 12-16) in Volume 1 of the 6.5 Grendel Reloading Handbook.

    You'll find that a number of questions you haven't thought of or posed are answered in Volumes 1 and 2 the the handbook.
    shootersnotes.com

    "To those who have fought and almost died for it, freedom has a flavor the protected will never know."
    -- Author Unknown

    "If at first you do succeed, try not to look astonished!" -- Milton Berle

    Comment

    • koden
      Bloodstained
      • Sep 2014
      • 92

      #3
      I look for spikes or erratic velocities from the Chronograph readings, ejector swipes, pieced primers and loose primer pockets. I keep an eye on the primer cratering and how flat the primers are but using CCI 450 primers I can go over pressure before the primers look bad sometimes. The Chrono readings are #1.

      Comment

      • LRRPF52
        Super Moderator
        • Sep 2014
        • 8569

        #4
        Biggest differences between loading for the AR15 and bolt guns is how important setting the shoulder back is, full-length re-sizing, primer seating depth, and powder/pill/weight combinations that are optimum for the gas system.

        You are already on the right track by knowing the ceiling with 8208XBR, and loading in .3gr increments. I like to use the 1% rule for charge weight increments:

        Case capacity x 1% = appropriate charge weight increment

        I use as many sources as I can find for load data, just to get some left and right ballpark limits established. Volumes I & II of the 6.5 Grendel Reloading Handbook series will really put you on solid ground as JASmith mentioned, and answer your questions about loading this cartridge for the AR15. Volume II has a series of specific discussions on:

        * Component selection, to include GTG (and stay away from) primers, shell holders, brass types
        * setting up dies
        * flash hole dimensions and de-capping rod considerations
        * case lubrication
        * Setting the shoulder back enough to function in a gas gun
        * Normal signs on necks that stick out to new gas gun reloaders
        * Scales and powder measures
        * Finding COL for mag-fed gassers
        * Bullet seating and trouble-shooting with dummy cartridges
        * Safety checks

        With a solid reloading background, transitioning to a gas gun can be pretty painless, as long as you set the shoulder back, find out where you are at with your chamber, and use hard/thick primers seated deep enough. There are so many loads in the handbooks, and your powder/bullet combo uses some of the more popular components. Looking forward to your results.

        Here's a link for the handbooks: http://ar15buildbox.com/Home_Page.html
        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

        • VASCAR2
          Chieftain
          • Mar 2011
          • 6219

          #5
          Just curious what dies your using? When using my Hornady dies to size Lapua cases I have to back the die up. If I leave my dies set to the same depth as I use for Hornady brass the Lapus brass gets a wrinkle down near the web. Lee dies are reported to over work 6.5 Grendel brass. Also Lapua brass uses a smaller flash hole and may need a smaller diameter decapping pin depending on the brand of dies your using.

          Comment

          • sneaky one
            Chieftain
            • Mar 2011
            • 3077

            #6
            acourvil- the signs are almost always the same for pressures. Once the small primer starts to slightly flatten-=that's normal. When the outer ring, around the primer really starts to disappear- - in diameter- then That's your true high pressure signs.. we call it the round groove gone. Plus the primer will be Flatter than Grannies flap jacks by then anyway!
            Plenty of sites to check this all out. Stay safe, always check the current load data on each bullet.

            Don't be a wild man like me out in left field doing bullet trials on your own. I have 20-30 yrs Of knowledge behind me from a major mfg. co. Shhhhh, I mean shhh! Goodies can be a comin!

            Comment

            • sneaky one
              Chieftain
              • Mar 2011
              • 3077

              #7
              Yes, acourvil., just follow the mfg. setup guidelines, it should be fine- if not - adjust die in to a slight --felt cam over- by arm strength notice----- to bump the shoulder back by an extra 1-2 k.

              .001-.002. Set the case into the chamber, let the BCG close onto the case- either good or bad will result. Too tight means screw the die in a tic, or leave as is, with good enuff results.

              Too tight means the bolt won't close fully, to rotate into a fully locked up battery mode. Safest position for all the fire groups to fully function is ,
              Remember the phrase - lock & load? Ammo is - Easy in, easy out dudes. Better to be a tic sloppy on loose specs,., than to be in troubles. I have 2 gray wolf packs on my hunt spot, lately. No need for tight chambered ammo here!

              They eat all the whitetails up- not much left for us. My ammo is a tic on the .001 looser side of my full on target ammo loads. Wolfie must lay down...
              Last edited by sneaky one; 10-31-2014, 02:36 AM.

              Comment

              • acourvil
                Warrior
                • Dec 2013
                • 112

                #8
                Thanks for the tips everyone. I already have the handbooks. I'm using redding dies, CCI 450 primers. Test loads are all set, now I just need some time at the range . . .

                Comment

                • Ullr
                  Unwashed
                  • Oct 2014
                  • 5

                  #9
                  What I am wondering most about is pressure signs. Since the max pressure for the Grendel is so much lower than with one of my bolt guns, what should I be looking for?
                  What you should be looking for is a pressure transducer. "Pressure signs" are meaningless nonsense. This is especially true of loads run thru AR-15s. Given that the weakest link is bolt strength, the first "pressure sign" that you may encounter is sheared lugs and catastrophic disassembly of the rifle. Conversely, lots of guns will show flattened primers, ejector swipes, and other alleged signs of impending doom even with starting loads, due to variation in action timing and other issues that are not pressure. Just about any safe max load will blow primers on the third or fourth loading of Wolf Grendel brass. Not excess pressure. Soft brass.

                  Relying on "pressure signs" is akin to dowsing for water with a bent stick, except in that a failure in dowsing does not involve releasing 60,000 psi and a cloud of shrapnel six inches in front of your nose.

                  Comment

                  • koden
                    Bloodstained
                    • Sep 2014
                    • 92

                    #10
                    Originally posted by Ullr View Post
                    What you should be looking for is a pressure transducer. "Pressure signs" are meaningless nonsense.
                    I think that is why manufacturers publish safe charge weights for various cartridges. They have done the pressure testing for us. The average reloader is not going to go out to spend thousands of dollars to get the sensors and jigs then drill holes in their barrels chamber so they can pressure test. Pressure signs in brass and primers are not meaningless. If your bolt breaks before any pressure signs then you had a faulty part.

                    To safely reload you need a Chronograph, some reloading manuals and common sense. Read the manuals and heed their advice. Barring the use of bolts imported from China you will be fine.

                    Comment

                    • Ullr
                      Unwashed
                      • Oct 2014
                      • 5

                      #11
                      This is a quote.
                      This is me responding.

                      I think that is why manufacturers publish safe charge weights for various cartridges. They have done the pressure testing for us. The average reloader is not going to go out to spend thousands of dollars to get the sensors and jigs then drill holes in their barrels chamber so they can pressure test.
                      No they sure wont. But often what they will do is fire untested loads, or substitute components, or otherwise risk their personal safety on the basis of "pressure signs" - and "pressure signs" are meaningless non sense - especially in an AR-15, and especially especially in an AR-15 chambered for a non-standard cartridge that weakens the bolt while simultaneously increasing bolt thrust per psi.

                      Pressure signs in brass and primers are not meaningless.
                      Yes they are. More importantly, the absence of "pressure signs", or the presence of "only mild pressure signs" are equally meaningless. Especially in an AR-15 chambered for a non-standard cartridge. You can get "pressure signs" when pressures are just fine, and you can break guns (sometimes in particularly unpleasant ways) with loads that don't show any "pressure signs" until catastrophic failure occurs. "Pressure signs" are not diagnostic.

                      If your bolt breaks before any pressure signs then you had a faulty part.
                      That just aint so. A dangerous belief, if put into practice.
                      Last edited by Ullr; 11-03-2014, 03:35 AM. Reason: reader request for clarity

                      Comment

                      • JASmith
                        Chieftain
                        • Sep 2014
                        • 1620

                        #12
                        Ullr, can you edit the previous post for clarity. It is hard to tell which comments are quotes and which are you opinion.

                        Some reloaders concur that inspecting fired cases for pressure signs can be misleading. On the other hand, there are a large number of folks who have used the technique with significant success when combined with other methods.

                        Also, the context of the discussion is the 6.5 Grendel. The SAAMI spec attached to the cartridge and chamber make it as standard as it gets
                        shootersnotes.com

                        "To those who have fought and almost died for it, freedom has a flavor the protected will never know."
                        -- Author Unknown

                        "If at first you do succeed, try not to look astonished!" -- Milton Berle

                        Comment

                        • NugginFutz
                          Chieftain
                          • Aug 2013
                          • 2622

                          #13
                          Whether for my 5.56, .223 Remington or my .264LBC, I can say without doubt that there are definite signs of pressure on the cases that is common to all of my gas guns. In all cases where I have seen ejector groove marks, I was at or near what I knew were max listed loads for the bullet and powder combination I was working with. Agree with me or not, this is one that I consider to be a valid indication. I agree that there may be pressure issues prior to that point, but it is certainly a red-flag, in my book.

                          Primer flattening is another matter, since various primers have different thicknesses and will show different levels of flattening for the same load. Reading primers seems as much art as it it is science, to me. Should pierced or popped primers show up, though, it is still an unmistakable red-flag. You've already gone where no reloader should go, and you're fortunate if those are the only indications you get.

                          Ultimately, it is every reloaders responsibility to exercise due diligence when working up a load that approaches published maximums, bearing in mind that those numbers are for a test setup you don't likely own. Obviously, this is why all credible sources exhort new (and old) reloaders to work up from ~10% below the max listed powder charge.

                          Just my $.03.
                          Last edited by NugginFutz; 11-01-2014, 03:15 AM.
                          If it's true that we are here to help others, then what exactly are the others here for?

                          Comment

                          • LRRPF52
                            Super Moderator
                            • Sep 2014
                            • 8569

                            #14
                            I have noticed quite a few hand loaders on other forums state:

                            "I was getting 2950fps with that load, no pressure signs at all, so I think this load will be my go-to! Man, this powder combo is great!"

                            Of course, the chronograph was 5ft from the muzzle, and who knows what their idea of "pressures signs" is.

                            This is why I try to find as many sources for data as possible, reference them with an understanding of the applied physics, and recognize the fact that we have lot-to-lot variations in powder chemistry, brass metallurgy, primer cup thickness and metallurgy, and projectile shaping.

                            The lot of powder X used in the tests published by a manufacturer may be dead on with yours, or it may not be. That's why I actually do like to begin with starting loads so I can get a baseline trend in the lower pressure regions, and see how that trend line forms as I work up in 1% case capacity increments, looking at velocity readings for each one.

                            For powder selection, I will go over all the available data for different powders that have been tested with the specific bullet that I am using, and find the ones that generated the lowest pressure, with the highest velocities. Those are indicators of a very efficient powder for that bullet, which translate into wider margins for accuracy nodes. 8208XBR under the 100gr class in the Grendel is a great example. CFE223 seems to be another for 123gr class as well, very forgiving.
                            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

                            • acourvil
                              Warrior
                              • Dec 2013
                              • 112

                              #15
                              O.k., the weather was pretty bad and the shooting conditions were a long way from being ideal, but I was able to get out and shoot through my test loads. Everything was shot prone using a bipod with a squeeze bag for rear support. All the test loads shot reasonably well; the worst group was just over 1 MOA. My two best groups were at 28.0 and 28.4, with 28.0 coming in at less than 1/2MOA and 28.4 coming just over 1/2MOA (but with 4 shots touching and one "flyer" that easily could have been my technique).





                              So I'm pretty happy with the results. I was not able to get good chrony info due to the weather/lighting, I'll have to pick that up in the next round. Based on the results, the next round will be in smaller increments from 27.8 to 28.5 (28.5 is Hogden's stated max for 123g projectiles).

                              Thanks again for the comments
                              Last edited by acourvil; 11-01-2014, 08:00 PM.

                              Comment

                              Working...
                              X