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  • Neck Tension & Crimping

    I've been doing some reading and noticed a statement on a site that said you should do a very light crimp on a 223 round so as to not deform the bullet in any way or your accuracy may suffer. That got me thinking...how do you ensure it's light enough to not deform the bullet yet heavy enough to prevent bullet setback on a semi-auto?

    I measured my case neck after resizing (.244) and after bullet seating (.246). I measured several rounds of different brass and it's the same across all brands. Would a light crimp be better than seating a bullet 3 hundredths deeper? I was seating at 2.260 which I hear most recommend much shorter. Seating at 2.230 would create more neck contact. I won't mention trimming to the high end of the range rather than the short end.

    What do you think? Seems like I should be able to measure the force associated with pulling or pushing a bullet to know the effect of either. Likewise, unless I cycle dummy rounds thru my guns several times, I'll never know if setback is occurring and to what extent.
    The ladder of success is best climbed by stepping on the rungs of opportunity.

  • #2
    Originally posted by Ragnar View Post
    I've been doing some reading and noticed a statement on a site that said you should do a very light crimp on a 223 round so as to not deform the bullet in any way or your accuracy may suffer. That got me thinking...how do you ensure it's light enough to not deform the bullet yet heavy enough to prevent bullet setback on a semi-auto?

    I measured my case neck after resizing (.244) and after bullet seating (.246). I measured several rounds of different brass and it's the same across all brands. Would a light crimp be better than seating a bullet 3 hundredths deeper? I was seating at 2.260 which I hear most recommend much shorter. Seating at 2.230 would create more neck contact. I won't mention trimming to the high end of the range rather than the short end.

    What do you think? Seems like I should be able to measure the force associated with pulling or pushing a bullet to know the effect of either. Likewise, unless I cycle dummy rounds thru my guns several times, I'll never know if setback is occurring and to what extent.
    Danged if I know.

    TECHNICALLY (splitting hairs damn fine here), you CANNOT Taper crimp and absolutely not "deform" (alter) the bullet at all.

    Any taper crimping (which I do) in order to get the case mouth to 'bite" the bullet, even a little, will "ring" the bullet slightly. SLIGHTLY.

    Thing is, as soon as you shoot that bullet, the rifling is going to put a full circle of .005" deep ribs into the sides of that bullet, so, "how much does a .003" deep taper crimp ring "deformation" REALLY matter?"

    The rifling will "deform" the bullet a lot more than the taper crimp will.

    I feed 3 autoloaders, an AR15, an LR308, and a BAR, everything gets a taper crimp or it gives me setback trouble.

    I crimp the case mouth down aprox (hard to measure) 2-4 thousandths (.002-.004") tighter than the case neck diameter beside the bullet. Lee Factory Crimp Die For Rifles.
    That translates, in case you miss the math, essentially 1 to 2 thousandths deep "crimp" all the way around the bullet.

    I am not of the opinion that this amount of "deformation" matters, ANY, and I am not trying to shoot a mile, or 2, or more.

    Your only other crimping option is cannelured bullets and roll crimp into that cannelure, but you instantly loose flexibility in bullet selection AND OAL.

    A lot of people insist on never ever seating "deeper", they always seat as close to the rifling lands as they can (a moot point to those of us who are limited by magazine-fed ammo).

    I TRY (some bullets defeat this) to seat the bullet 1-caliber deep in the case (a boat-tail needs to go deeper to do this because the BT does not count), but then, as I said, my autoloaders get crimped ammo.

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    • #3
      Thanks for the response. The point about the rifling makes sense. I have the Lee Factory Crimp Dies for all my rifles but never gave this much thought. I think what I may do is do a very light crimp like you note as well as seat the bullet a couple hundredths deeper and see how muzzle velocity and accuracy look. I have velocities for all my loads at 2.260 COAL and current crimp. Might just cycle a full magazine 2 or 3 times and measure COAL to see if there is any change. The furthest I'm shooting right now is 200 yards. But I feel it's never too early to get a finer understanding of handloading.
      The ladder of success is best climbed by stepping on the rungs of opportunity.

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      • #4
        Ragnar, just cycling the rounds through the action by hand is not going to do the trick if you are looking at what causes the setback in autoloaders. The dynamics are way different when you fire the rifle as opposed to just tugging at the charging handle.

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        • #5
          I've never come across an auto loader rifle that I needed to crimp for, and IMHO if when cycling the same rounds (measure prior) multiple times you aren't seeing any significant set back, then crimping shouldn't be necessary. If OTOH you're getting set back that's approaching in excess of say .005" and upward of .010" then you probably do need a crimp. For a realistic assessment I would live fire cycle test for set back, manually cycling isn't really going to produce the amount of inertia and feeding impact that's experienced during typical operation when firing the weapon.

          To eliminate bullet tip deformity from contaminating the results, use your seating stem to measure set back off of the ogive. To do this, simply seat the bullet to the depth you'll be shooting, then remove the die, measure from stem to mouth of die. After cycling the cartridge or cartridges, put them back in the press, extend ram as if seating the bullet, now adjust the stem down, if it is able to be adjusted down, thread it completely down to make good firm contact with the bullet ogive, remove die and measure again. the difference, if any, represents set back.

          HBC

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          • #6
            It seems that everyone is worried about set back as the reason for crimping or not crimping an auto rifle. I am just as worried about bullets jumping forward when the bolt slams home in a manner not unlike a kinetic bullet puller. I have had bullets in a Remington .270 auto stick in the lands when I tried to unload the gun. I had plenty of clearance from the lands when I set the dies, I did not crimp autoloaders then. I do so now. RD
            Every once in a while in life we need a policeman, a lawyer, a doctor and a preacher. We need a farmer three times a day, every day.

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            • #7
              My issue isn't and never has been 'set back' thar people attribute to recoil forces.

              None of my rifles kick so hard they bash bullet tips against magazine front walls.

              What I had occur was bullets 'driven' back by the ride out of the magazine, whatever it bash rattled against on the way into the chamber, whatever chamber shoulder bouncing it did.

              I had it happen manually cycling Gallery Loads as well as full power ammo.

              The early days of learning to set .308 dies properly, got a few large cases that wouldn't close fully into battery. I would just unload them and move on.
              It isn't too hard to get a 150gr soft point back out of a case when a third of it still sticks out from atop 44gr or so of imr4064, but try getting a 100gr Short Jacket back out when it is shoved completely in so that it rattles atop 17gr or so of Red Dot.
              A .223 SABOT down on 30-some grains of powder.
              No way to push or pull it out.
              It's been long enough I don't recall how I got it out, or if I even did. I may have thrown it away.

              I haven't had a bullet shoved backwards into the case in 3 decades, not 0.005", not 0.500".

              I can usually work my crimped ammo down to under MOA so crimping isn't killing my accuracy.

              Comment


              • #8
                This one's been covered many times, but here goes.
                I load for and shoot a load of ARs and shoot uncrimped ammo, by the 10s of thousands.

                With proper neck tension, you don't need crimp, even for AR. If you don't have proper neck tension, crimp isn't going to fix it. Maybe crimp doesn't hurt your accuracy, go to high power or service rifle comp and see how many crimp, their rounds.

                I do an insurance crimp, on SHTF and defense rounds, for AR and that is just "turning" the edge, if you could measure it, it would be ~< .001", just like crimp on pistol, just turn the edge, so it doesn't drag while feeding.

                I've only had bullet movement, on one batch of reloads using "pulled" bullets, that were out of spec, varying from .223" to .2235". These were ss109 and the steel core, affected neck hold, in effect expanding necks, with bullets, during seating.
                If we don’t speak out against the infringements of today, it will weaken our ability to stop the next infringements.
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                • #9
                  I'm a reformed crimper: used to all the time for my AR rounds. Still have boxes of them. Then one day I thought, let's see what happens when I don't: they all went bang and went where I sent them....

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                  • #10
                    I have the perfect solution:
                    Don't shoot semi-autos......
                    Wimachtendienk, Wingolauchsik, Witahemui

                    He who knows not and knows not that he knows not, is a fool.
                    He who knows not and knows he knows not, is wise.

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                    • #11
                      Interesting perspectives by everyone. I may make up a batch seated deeper but no crimp just to compare. It's hard to imagine a crimp of .001 would make any difference though. Given how long my COAL is I feel I have some room if there were a few hundredths setback. Many of the load reference data are at 2.200 or thereabouts so unless I have a major issue it would seem I would need a significant crimp to prevent that much movement.

                      Measuring to the ojive is a great idea. I have the Lee OAL gauge and will manually cycle some rounds just to see. I understand this isn't real world as noted, but if something shows up it's better discovered here than in live fire.
                      The ladder of success is best climbed by stepping on the rungs of opportunity.

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                      • #12
                        They say a picture is worth a 1000 words, so here it is. Millions upon millions of rounds of ammo were loaded for the autoloading Garand rifle, all with bullets crimped and sealed. But when loaded for accuracy the arsenals knew full well from experience that crimping the bullet was not good. Which is why match ammo for the Garand was never crimped, as shown here.

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                        • #13
                          [QUOTE=RobertMT;n814908]This one's been covered many times, but here goes.
                          I load for and shoot a load of ARs and shoot uncrimped ammo, by the 10s of thousands.

                          With proper neck tension, you don't need crimp, even for AR. If you don't have proper neck tension, crimp isn't going to fix it. Maybe crimp doesn't hurt your accuracy, go to high power or service rifle comp and see how many crimp, their rounds.

                          I do an insurance crimp, on SHTF and defense rounds, for AR and that is just "turning" the edge, if you could measure it, it would be ~< .001", just like crimp on pistol, just turn the edge, so it doesn't drag while feeding.


                          This is exactly the same experience I've had for decades Robert, never once have I experienced any problems, be it set back or pull. I'm a jammer, in many of the rifles I load for I jam them into the lands. I also turn and ream my necks to attain more consistent neck tension, and in some instances I reduce neck tension down to very minimal levels, yet I've never pulled a bullet out of the neck when extracting a live cartridge. I also uniform / turn necks for AR's, this does reduce neck tension some, and still none have moved.

                          And I also couldn't agree more with regarding neck tension, crimping does not fix poor neck tension, and if one does try to increase neck tension by applying more crimp, neck tension will be diminished. This isn't just my opinion, but it's also supported in hand loading books, exception I've found was in a Sierra manual, in which it was stated that a firm crimp should be applied to 9mm to prevent set back, nope, not a good idea IMHO. I do sometimes touch the mouth on rimless handgun cartridges, just enough to close the bell, but I wouldn't term it as a crimp, nope, it really isn't a crimp. Roll crimping revolver brass is necessary, but that's a whole different application, bullet pull can be a real concern with some loads, and it provides a more consistent powder burn.

                          Now this whole factory crimp die thing, maybe that does increase or produce more neck tension, don't know, never used one, but I've never needed one either. They didn't exist when I started into this hobby, and considering I've never experienced a problem, I saw no need to fix an issue that didn't exist in the first place.

                          HBC

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                          • #14
                            Originally posted by Offfhand View Post
                            They say a picture is worth a 1000 words, so here it is. Millions upon millions of rounds of ammo were loaded for the autoloading Garand rifle, all with bullets crimped and sealed. But when loaded for accuracy the arsenals knew full well from experience that crimping the bullet was not good. Which is why match ammo for the Garand was never crimped, as shown here.
                            The thing with that comparison though is all Garand ammo was ROLL crimped, into a cannelure.

                            Taper crimp is different.

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                            • #15
                              Originally posted by Damannoyed View Post

                              The thing with that comparison though is all Garand ammo was ROLL crimped, into a cannelure.

                              Taper crimp is different.
                              Not all ammo loaded for Garand was crimped. Match ammo loaded for Garand was not crimped in any way. The bullets used in match ammo had no cannelure. Consult photo above.

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