How much crimp on a .223 for an AR

Discussion in 'Reloading Forum (All Calibers)' started by Cameron SS, Jul 19, 2011.

  1. Cameron SS

    Cameron SS

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    I have recently started reloading for my AR. I've got some 77 gr SMKs(cannelured) that I would like to work into a good service rifle match load that I will use out to 600 meters.

    I'm using once fired military brass that I picked up on the cheap. Accuracy to date has been decent, but I have noticed that bullets seated in the bottom of a mag, after firing about 8 or 9 rounds out of the mag, will measure a few thou deeper then what I seated them at. Recoil setting the rounds back is my best guess, and I figure crimping or increasing neck tension are two possible solutions.

    I've read extensively on the controversy of to crimp, or not to crimp, and have decided I will give it a try and see for myself.

    Not actually having used the crimp ring in my RCBS seater die, I'm probably going to pick up the redding taper crimp die, but not until I'm sold on it being something I'll actually use.

    Long question short, how much crimp do people put on their necks? Are we talking a few thou, .01", .05". Is there a sweet spot?

    Thanks gents, looking forward to the responses.
     
  2. mj2evans

    mj2evans

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    I shoot some service rifle (223) and don't crimp at all (using Foster FL sizer). Feels like plenty of neck tension for me.
     
  3. KevinThomas

    KevinThomas

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    Cameron SS,

    The answer is none at all, but that assumes you have sufficient neck tension to begin with. From what you've said about your bullets moving under recoil, it sounds that you don't, and I'd want to correct that first. Bushing dies will work, as will honing out the neck of a standard sizing, but that's a bit more limiting; it limits you to using brass with neck thicknesses compatible with whatever diemnsion you honed the neck out to, period. The bushing die will give you some latitude there, and I suggest that as a better fit. If you do want to crimp, less is better, no matter which type you choose to apply. Taper crimpers are good, and readily available, and don't overlook the Lee Factory Crimp Die. Work with your neck tension first, would be my suggestion, but if you decide you really want to crimp, just don't over do it.
     
  4. spclark

    spclark Site $$ Contributor

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    Bumping neck tension ought to be your first move. Nobody I know who shoots service rifle uses crimped rounds.

    Bullet makers go to a LOT of trouble to provide consistent bullets; crimping (even taper-crimping) can change the surface dimensions of seated bullets all too easily & that's going to affect accuracy a great deal more than a few thousandths more jump or a bit more pressure upon firing.
     
  5. markm87

    markm87

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    None for me on good bullets. Light Factory Crimp on 55 grain FMJBT W/Cs.

    I've read accounts of people getting improved performance by crimping a little. Depends on your neck tension variations I suppose.
     
  6. Erud

    Erud Site $$ Contributor

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    Another vote for no crimp. FL bushing die should fix your trouble.
     
  7. fdshuster

    fdshuster Site $$ Contributor

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    And, yet another vote for no crimp. I've fired many thousands of rounds from my AR's in CMP & NRA High Power match's and not a single round was crimped ( no crimp groove on my Sierra match bullets anyway), and have never had to call an alibi for an ammo/rifle malfunction. Also loaded 30-06 for my M1 Garand for a few years, and again, never crimped. But, as others have said, I use plenty of neck tension.
     
  8. Scott Harris

    Scott Harris Site $$ Contributor

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    No crimping again. I size .003 below loaded diameter and run a mandrel through that is .002 less than loaded diameter. Bullets are very firmly seated.
     
  9. Cameron SS

    Cameron SS

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    OK, So the consensus is what I figured, stay away from the crimping. I'll look into the bushing neck dies. I have them for my .300 WSM, so am very familiar with those. I initially thought they'd be a bit much for my lil ole AR, but good kit is good kit.

    That said I want to do an experiment now anyways. I expect that any variations in neck tension from neck length (which should be minimal with my power trimmer,) would be added and magnified by a crimp. I would expect to see a decrease in accuracy with crimping

    How much is a light crimp?
     
  10. 2506

    2506

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    I have to buck the consensus. I use the Lee Factory Crimp Die with non-cannelure Sierra match 52 and 69 gr Match Kings and get better accuracy than with non-crimped rounds. I have found that if you leave the case 5 thousands longer than the trim to length it gives you enough case neck to allow a good bite on the case to get a good crimp. I have also found a great increase in accuracy with many of the old military rifles that have long throats where the bullet must jump a good ways with using the Lee Factory Crimp Dies. Give them a good honest try and you just might be surprised.
     
  11. seanhagerty

    seanhagerty

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    I'm going to go against the grain as well. I use a Lee factory Crimp Die and a product called Consistent Crimp that allows me to measure the amount of pressure (in Ft-Lbs) I apply to each crimp. I use this on rounds I load for my AR and found that it shrunk my groups by about .25 inch at 100Yds.

    At the amount of pressure I apply I have found no deformation on the bullet itself. This has been verified by pulling several rounds after loading and crimping.

    I say you should try crimping a few to find out if it works for you.

    Sean
     
  12. people

    people

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    I put a very light crimp on my 77gr bullets.

    If you go to http://www.usrifleteams.com/ you may find very different responses than from this group. Granted many of us are on both sites. It seems to work or it does not. There does not seem to be any middle ground on this.
     
  13. Erud

    Erud Site $$ Contributor

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    I'm sure you just mis-typed, but just for clarification, make sure to get the Full-Length bushing die as opposed to just the neck size bushing die for the AR.

    Good luck,
    Erik
     

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