Make life easier on yourself with a headspace comparator bushing

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  • Klem
    Chieftain
    • Aug 2013
    • 3509

    #16
    Originally posted by lrgrendel View Post
    This is a great thread! 52 and KLEM great explanation.

    So I am going to a bolt only now. I have a Forster FL sizing die and I always FL sized because I was only shooting a gas gun.

    Please explain the technique I now need to do i.e. Half FL. Ideally I would get a neck sizing die as I have for my other bolt action rifles but I would like to try this out.

    Thought I was the only one with that Lyman calibers! Mine must be 20 years old!
    lrgrendel,

    If you have a bolt gun and want to stick with your FL die then I would set up the die first. Start with your die unscrewed a couple of turns. Lube a fired case and size it. Then load it in the gun (no bullet, just the empty case) and try and close the bolt (don't force it). If it doesn't go into battery repeat this sequence while screwing the die in 1/4 turn each time, until the bolt finally closes. You can fine-tune it at this stage and then secure the locking ring and you are set.

    This means you are sizing both the neck and case but only to the bare minimum to close the bolt. You can measure the headspace with your comparator but no doubt it will be less than the .003"+ in gas guns. Maybe .001". The neck might not be sized all the way to the shoulder but it will be pretty close. This is a good thing as it helps centre the case in the bore.

    Some bolt gunners even attempt half-sizing with neck-sizing dies. By that I mean they size only half the length of the neck. So half is holding the bullet and the other half is left fire-formed for a tighter fit in the chamber. This means there is less surface area tension holding the bullet but with bench-resters who gently load their bullets one at a time this is an option.

    Comment

    • lrgrendel
      Warrior
      • Jul 2013
      • 662

      #17
      Originally posted by Klem View Post
      lrgrendel,

      If you have a bolt gun and want to stick with your FL die then I would set up the die first. Start with your die unscrewed a couple of turns. Lube a fired case and size it. Then load it in the gun (no bullet, just the empty case) and try and close the bolt (don't force it). If it doesn't go into battery repeat this sequence while screwing the die in 1/4 turn each time, until the bolt finally closes. You can fine-tune it at this stage and then secure the locking ring and you are set.

      This means you are sizing both the neck and case but only to the bare minimum to close the bolt. You can measure the headspace with your comparator but no doubt it will be less than the .003"+ in gas guns. Maybe .001". The neck might not be sized all the way to the shoulder but it will be pretty close. This is a good thing as it helps centre the case in the bore.

      Some bolt gunners even attempt half-sizing with neck-sizing dies. By that I mean they size only half the length of the neck. So half is holding the bullet and the other half is left fire-formed for a tighter fit in the chamber. This means there is less surface area tension holding the bullet but with bench-resters who gently load their bullets one at a time this is an option.
      Klem.

      Again thanks for the detailed answer to my question.

      Before I try what you said. Won't my brass fit in my chamber even if I don't size them?
      Since they were fired in that gun?

      Comment

      • Klem
        Chieftain
        • Aug 2013
        • 3509

        #18
        Originally posted by lrgrendel View Post
        Klem.

        Again thanks for the detailed answer to my question.

        Before I try what you said. Won't my brass fit in my chamber even if I don't size them?
        Since they were fired in that gun?


        Yes, fair point. Spent cases from that gun will close on the bolt nicely without any sizing...unless it was a really hot load and when you unlocked the bolt it felt sticky and took a bit of effort. I have experienced this with 338L where not only the case expands but the whole chamber with it. In that case cases never retracted to their original size and it was hard work opening the bolt every time. Full length sizing was the go and cases didn't last long. The gun was a Remington 700 LA Police X, which is no longer available (probably because they realised the action just wasn't up to it).

        In your case you are using a FL die on a bolt gun with cases that only need to be neck sized to hold the bullet. All you need do is screw that die in to where you are comfortable it is holding the bullet enough for your intended use (at the bench, out in the bush?). Whatever length you decide will unlikely bump the shoulders at all - but it might squeeze a bit of the case diameter down towards the web. Can't be helped with a FL die and won't hurt it at all. Certainly better than taking it all the way back to SAAMI.

        So, no quarter turns if you have a bunch of cases already fired from the same gun.
        Last edited by Klem; 08-22-2017, 11:53 AM.

        Comment

        • xlcc
          Warrior
          • Feb 2016
          • 210

          #19
          I don't have or use the gauges for setting my dies for my Howa mini,don't have a gas gun so can't comment on that.I use fired cases from my gun when setting up my dies.I then smoke the neck and shoulder area of the case useing a candle.I do about 5 or 6 cases then let them cool as the candle flame may change the case size a bit.Next I carefully chamber a smoked case and extract the case trying not to smudge the the smoked shoulder.What I am trying to see is a case that has the shoulder smoke just swiped then adjust the die down about an 1/8 turn at a time and resmoke the shoulder area again and retry the procedure until the case chambers easily and barely smudges the shoulder.At that point those cases are set to about zero headspace with a full length sizer die.If I have any cases that "feel" a bit tight when chambering I will adjust the die down another 1/8 turn and call'er good.Not all fired cases will be exactly the same length so for reliability the die must be set down enough for all cartridges to chamber easily.
          I use this procedure and achieve great accuracy and reliability but to be sure when useing my ammo for hunting or defense I chamber every loaded round before I need to use it.

          Comment

          • Kswhitetails
            Chieftain
            • Oct 2016
            • 1914

            #20
            So, when using the term "bump the shoulder back" what we are discussing is the action the sizing die makes in pressing the shoulder "back" toward the web of the case in essence pushing the case back down when the case is pressed up into the die. Have I understood correctly this time?

            So, what the comparator does, is to gauge the length of the case from the datum line of the shoulder (half way point from body to neck) of a spent case. Then, we compare this length to the origin spec or unfired length of virgin brass, or even better, to the actual head space of the particular chamber in question.

            And, because we want the extra "slop" in the chamber on gas guns, we want to FL size the gas gun cases back to the original (saami?) spec size so that they can be fed and extracted more easily in the SA action because there is no "bolt lever" to compound the leverage required to unlock the bolt and extract the case?

            So, to "bump" the shoulder back we just adjust the FL die down toward "cam-over" further; each adjustment down on the size die "bumping" the shoulder back a little further. Thus, using the comparator gauge, we can measure the exact amount of sizing reasonable and set the FL size die a little higher in the "Cam over" as to work the brass less and therefore lengthen the life span of the brass while maintaining gas gun feeding reliability?

            Does this make cartridge case gauges obsolete?
            Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

            Comment

            • LRRPF52
              Super Moderator
              • Sep 2014
              • 8569

              #21
              Originally posted by Kswhitetails View Post
              So, when using the term "bump the shoulder back" what we are discussing is the action the sizing die makes in pressing the shoulder "back" toward the web of the case in essence pushing the case back down when the case is pressed up into the die. Have I understood correctly this time? Yes

              So, what the comparator does, is to gauge the length of the case from the datum line of the shoulder (half way point from body to neck) of a spent case. Then, we compare this length to the origin spec or unfired length of virgin brass, or even better, to the actual head space of the particular chamber in question. Yes

              And, because we want the extra "slop" in the chamber on gas guns, we want to FL size the gas gun cases back to the original (saami?) spec size so that they can be fed and extracted more easily in the SA action because there is no "bolt lever" to compound the leverage required to unlock the bolt and extract the case? We don't want to size back down to virgin, minimum shoulder location brass, as this will excessively cold-work the brass and also cause more bolt thrust. As the pressure peaks, the elastic brass alloy expands in all directions, including back against the bolt face. It also can push the primer against the bolt face first violently, and cause primer flow into the firing pin aperture, followed by the brass expanding and filling over the primer again, re-seating it. Think of brass as a high pressure gasket in the chamber that changes dimensions significantly in the paths of least resistance.

              So, to "bump" the shoulder back we just adjust the FL die down toward "cam-over" further; each adjustment down on the size die "bumping" the shoulder back a little further. Thus, using the comparator gauge, we can measure the exact amount of sizing reasonable and set the FL size die a little higher in the "Cam over" as to work the brass less and therefore lengthen the life span of the brass while maintaining gas gun feeding reliability? Yes, incrementally turn your sizing die down until you have reached the optimum headspace setting for your chamber that will allow reliable lock-up into battery, without excessively working the brass.

              Does this make cartridge case gauges obsolete?
              Using a stripped down bolt, you can determine your lock-up as you incrementally size the brass down, so the rifle's actual chamber becomes your headspace gauge in combination of the comparator tool. One mistake that is easy to make is to size your brass, drop it in the chamber, see if it falls out, and call it good, but you don't know if the bolt will lock into the extension with that piece of brass.

              This is why I like the comparator tool and a stripped bolt, so I can measure everything exactly and establish where I'm at before nailing down the sizing die.
              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

              • Kswhitetails
                Chieftain
                • Oct 2016
                • 1914

                #22
                I think I finally follow!!! I finally find myself understanding this "head space" (.125 vs .136 -type I, II) argument much better, too. Though, I don't think I could explain it, so maybe some of the missing parts of the puzzle are in place?

                Awesome, thanks.

                ( I don't learn so well from the abstract, I need to go feel it. The phone and I are headed to the shop to turn some bolts...)

                When my rifle comes in, I'll post what I can figure out, and accept any and all instruction. All in order to get the best reloads I can for it. I am really looking forward to this new endeavor.
                Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

                Comment

                • Dave_H
                  Unwashed
                  • Jun 2017
                  • 24

                  #23
                  Originally posted by LRRPF52 View Post
                  Using a stripped down bolt, you can determine your lock-up as you incrementally size the brass down, so the rifle's actual chamber becomes your headspace gauge in combination of the comparator tool. One mistake that is easy to make is to size your brass, drop it in the chamber, see if it falls out, and call it good, but you don't know if the bolt will lock into the extension with that piece of brass.

                  This is why I like the comparator tool and a stripped bolt, so I can measure everything exactly and establish where I'm at before nailing down the sizing die.
                  By stripped down I "assume" you mean ejector removed and the extractor still in place to pull the case from the chamber. Or, do you remove the extractor also and then punch the case out of the chamber from the muzzle end with a cleaning rod or other rod of some type?

                  Comment

                  • Kswhitetails
                    Chieftain
                    • Oct 2016
                    • 1914

                    #24
                    I think the empty brass should fall out of the chamber, just like a case gauge. That's the way I understand the sentiment.
                    Nothing kills the incentive of men faster than a healthy sense of entitlement. Nothing kills entitlement faster than a healthy sense of achievement.

                    Comment

                    • lrgrendel
                      Warrior
                      • Jul 2013
                      • 662

                      #25
                      Originally posted by LRRPF52 View Post
                      A lot of people have been asking about sizing, how to approach it, do I cam over, smash the shell holder to the bottom of the sizing die, do I use a case gauge, etc.

                      I think this method really cuts to the core of what we're trying to do with sizing, namely where we're placing the shoulder so we get consistent headspace that will actually fit in the chamber and allow the bolt to lock over the reloaded cartridge. For the 6mm PPC family and its .350" datum line on the center of the shoulder per SAAMI, we use the .350 bushing provided by Hornady in the kit.

                      I thought some pics of how the process works would be worth a thousand words:

                      Bushing installed in my calipers, indicated to 0.000" off the 2" mark, which is the length the tool will fill between the blades after being installed.

                      L-R: Unfired AA 123gr Scenar load, 1x fired Lapua brass, reloaded cartridge with enough shoulder setback to chamber and lock-up



                      Unfired Lapua brassed cartridge headspace measurement: 1.205"




                      Fired Lapua brass, unsized headspace measurement: 1.218"




                      Sized to fit and lock-up in my chambers with a bolt that has the ejector removed: 1.210" (I can get away with 1.212" and still lock up, so this is a little excessive sized back .008")


                      So I did a little exercise and it worked out very well. Sized 6 cases.

                      2 with the shell holder touching the die. Neck was fully sized.
                      2 with die backed out one turn. Neck was 2/3 sized.
                      2 with die backed out two turns. Neck was 1/3 sized.

                      I coloured the neck of one case from each group with a sharpie.
                      I hope you can see the results in the photos. It is very obvious.

                      I ended up full length sizing one case as I used to do just to see....

                      From now on, for my Howa Mini action BOLT gun, I will back off my Forster FL sizing die one turn.
                      Sizing of the die and 2/3 of the neck is perfect as in the photos.

                      One again great thread, thanks. I'll hold off buying a neck sizing die and see how this works out.....
                      Last edited by lrgrendel; 08-22-2017, 08:18 PM.

                      Comment

                      • Klem
                        Chieftain
                        • Aug 2013
                        • 3509

                        #26
                        I can add something here...

                        Originally posted by Kswhitetails View Post
                        So, when using the term "bump the shoulder back" what we are discussing is the action the sizing die makes in pressing the shoulder "back" toward the web of the case in essence pushing the case back down when the case is pressed up into the die. Have I understood correctly this time? Yes

                        So, what the comparator does, is to gauge the length of the case from the datum line of the shoulder (half way point from body to neck) of a spent case. Yes, any case - not just spent.Then, we compare this length to the origin spec or unfired length of virgin brass, or even better, to the actual head space of the particular chamber in question. Yes, that is one meaningful metric you can get by comparing the datum-base length of a fired case to either new brass or factory loads. Another metric is the all-important headspace of your chamber. For this you compare a fired case with whatever your die gives you after sizing. You vary this of course by screwing in and out your die.

                        And, because we want the extra "slop" in the chamber on gas guns, we want to FL size the gas gun cases back to the original (saami?) spec size so that they can be fed and extracted more easily in the SA action because there is no "bolt lever" to compound the leverage required to unlock the bolt and extract the case? Yes, you can FL back to SAAMI if you want but many of us settle for somewhere less than that, to maximise case life and precision. We don't go all the way back to SAAMI. We only squeeze/bump the datum/base by .003"+ and you need a comparator to be able to measure this.

                        So, to "bump" the shoulder back we just adjust the FL die down toward "cam-over" further; each adjustment down on the size die "bumping" the shoulder back a little further. Thus, using the comparator gauge, we can measure the exact amount of sizing reasonable and set the FL size die a little higher in the "Cam over" as to work the brass less and therefore lengthen the life span of the brass while maintaining gas gun feeding reliability? Whether your loading press cam's-over depends on the brand and the shell holder you are using. You can do all this on a press and it might not cam-over. The good thing about camming-over is that it gives you exactly the same result every time. It doesn't rely on the operator pressing the handle with exactly the same pressure each time. If you keep screwing your die in it will probably get to the stage where the handle cannot cam over (don't force it). Hopefully this doesn't happen at the point where you have decided is the best spot for the die to reach. In our case with backing it out one turn that hasn't happened so all good.

                        Does this make cartridge case gauges obsolete? No (although 52 has said previously he doesn't use them) - I use both, but you don't need both. If I had a choice of only one I would buy the comparator as it gives precise metrics of all these important measures. Rifle gauges are more limited in that you go more by feel and there are only two or three levels built in by the manufacturer related to Go/NO GO. But, they are cheaper than a combined set of calipers and the comparitor. Plus they give a quick sense of axial headspace or the diameter of the case. Sheridan apparently uses chamber reamers to make theirs while Lyman goes a bit more sloppy in internal diameter to fit all cases. With Lyman gauges like their 223 I put the case in, hold it up to my ear and shake it like a castanet to get a feel of how much axial headspace there is in the case. Not very scientific I know but it works. I use rifle gauges only as ready-reckoners when cranking out high volumes on the press. That said, you need a set of calipers if you hand-load so that's one cost you've already paid for.
                        Your photos on your next post look good so I don't doubt that bolt gun will be harvesting some fine meat shortly.
                        Last edited by Klem; 08-22-2017, 10:42 PM.

                        Comment

                        • Redomen
                          Warrior
                          • Jun 2016
                          • 568

                          #27
                          I measured fired cases at 1.216 and re measured after sizing and they stretched to 1.217 and 1.218. Guess I need to bump more?

                          Comment

                          • Klem
                            Chieftain
                            • Aug 2013
                            • 3509

                            #28
                            Originally posted by Redomen View Post
                            I measured fired cases at 1.216 and re measured after sizing and they stretched to 1.217 and 1.218. Guess I need to bump more?
                            If they function reliably in your gun I wouldn't bump them any further. If there are issues, then yes, you can screw it in a bit more.

                            Comment

                            • LRRPF52
                              Super Moderator
                              • Sep 2014
                              • 8569

                              #29
                              Originally posted by Redomen View Post
                              I measured fired cases at 1.216 and re measured after sizing and they stretched to 1.217 and 1.218. Guess I need to bump more?
                              Does your stripped bolt rotate closed on those sized cases? If not, size down incrementally until they do.

                              If it rotates closed on a sized case in your chamber, then you have successfully sized it for your chamber.
                              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

                              • Cornbread
                                Warrior
                                • Dec 2015
                                • 288

                                #30
                                Originally posted by Redomen View Post
                                I measured fired cases at 1.216 and re measured after sizing and they stretched to 1.217 and 1.218. Guess I need to bump more?
                                It is quite common to see this number go up. The shoulder is moving slightly forward making the measurement go up a tad. Keep screwing the die in until the number decreases approx .003.

                                Using some sort of a comparator( I use the Hornady) is essential for reloading safety. Blindly resizing cases back to minimum spec can create excessive headspace and cause case failure.

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