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223 Full Length Resizing

Discussion in 'Handloading and Reloading' started by Hondo 60, Jan 2, 2014.

  1. Hondo 60

    Hondo 60 Well-Known Member

    The standard answer on this forum is that we need to "full length resize" or "FLR" when shooting from an AR.

    I don't know that its ever been answered, but why?

    I FLR just cause that's the pat answer here.
    AFAIK, no one's ever said why.
  2. Walkalong

    Walkalong Moderator

    Feeding and chambering. A bolt gun has a lot of leverage to close on a tight case, the AR does not. It needs clearance. Even "sloppy" GI chambers.
  3. Rule3

    Rule3 Well-Known Member

    I asked that question some time ago. So neck sizing is fine when used in the same Bolt gun as it forms to that chamber.

    Why is it not just as fine if used in the same semi auto gun? Isn't it fire formed to the chamber of that semi auto as it is to the bolt gun??

    It comes up from the mag and is slammed forward into the chamber same as bolt only it does it automatically and with more force.

    So I still do not get it, I follow the procedure, but still confused.

    That is the million dollar question.;)
  4. tnelson31

    tnelson31 Well-Known Member

    The brass is still expanding when it is yanked out of the chamber.
  5. readyeddy

    readyeddy Well-Known Member

    FLR is recommended when you need reliable feeding, e.g. hunting. This is because neck sizing only can result in tight fits that may result in a jam.

    So if you don't mind having your semi auto jam, then neck sizing only may be for you and hopefully give you increased accuracy.
  6. Slamfire

    Slamfire Well-Known Member

    Case clearance is something that is carefully studied in military actions. This clearance is 100% critical for reliable function and safety.
    This chart came from AMCP 706-247 “ Ammunition Series, Section 4, Design for Projection”, I highly recommend reading starting section 4-76 Cartridge case and Chamber Design”

    Many bolt gunners are able to get away with reloading techniques that will positively jam a semi automatic mechanism. Some think as long as they can beat the bolt closed and knock it open with a block of wood, they have demonstrated expertise in reloading. Neck sizing, partial neck sizing, etc, these reloading techniques will work with manual mechanisms for a time but in time even beating down the handle won’t close the bolt and the case will be so stuck in the chamber that a cleaning rod is required to knock the case out.

    Factory case dimensions will provide the highest degree of function in a semi automatic mechanism. Cases that are larger than factory are more likely to drag in the chamber causing a failure to extract. Full length sizing in a standard die will not reduce the case to factory dimensions, a small base die gets it closer.
  7. edfardos

    edfardos Well-Known Member

    Anyone actually try partial necsize in a semi auto? I bet iit's fine with harder/older brass.
  8. Trent

    Trent Resident Wiseguy

    I full length size 223.

    I small base size 308 win. (THAT, is a positively good workout, by the way. Takes a lot of effort.)
  9. cfullgraf

    cfullgraf Well-Known Member

    Personally, I would not try partial neck resize in an AR. I have had enough cases stuck in one of my ARs that a full length sizing die did not size them enough.

    It is no fun getting the stuck cases out.

    But have at it if you want to try it.
  10. Ifishsum

    Ifishsum Well-Known Member

    In a semi-auto rifle, case ejection is often starting before the brass has contracted and is fully released from the chamber walls. This means your brass is usually stretched more than it would be in a bolt rifle, and won't usually fit easily back into the same chamber it was fired from. The body is usually fatter and longer to the shoulder datum than the chamber itself, and can cause cases to stick on loading, preventing the bolt from closing completely and can occasionally even cause a slam fire.
  11. Walkalong

    Walkalong Moderator

    Yep. Don't take our word for it. :)
  12. Rule3

    Rule3 Well-Known Member

    Thank you.
    This is the closest to an actual explanation or answer yet.:)

    Try it, or I wouldn't do it, really is no answer. Both the OP and myself were trying to understand why. No one is beating on a bolt or trying to get a case to fit. or take anyones word for it, simply explaining it is nice. As mentioned I do FL size for semi autos, why ? Because we always do it that way.:rolleyes:
  13. Walkalong

    Walkalong Moderator

    And we told you, the auto needs the round to chamber easily, as in clearance the bolt gun doesn't need. You only get this with full length sizing. It's really simple.
  14. GLOOB

    GLOOB Well-Known Member

    The answer is pretty darn obvious, if you have done enough neck sizing for a bolt rifle. Eventually, you have to FLR, right? When do you do this? When it becomes difficult to close the bolt. That's fine on a bolt action, cuz all you have to do is press harder.

    Well, you could wait for your AR to start jamming, but by then you might have a round light off OOB. Apparently, the design of the AR can allow a round to fire (or slam-fire, maybe? I'm not sure of the specifics.) even before the locking lugs have engaged.

    Even if it were completely safe, who wants the increased risk of a jam? Now add the way that AR's spit out brass, how could you even be sure that every piece of brass you reloaded was fired out of the correct gun? Even if you kept track of number of firings to be able to bump the shoulders back before problems arose, you'd have to figure out how to keep stray pickups from infecting your brass.
    Last edited: Jan 3, 2014
  15. cdb1

    cdb1 Well-Known Member

    "This means your brass is usually stretched more than it would be in a bolt rifle, and won't usually fit easily back into the same chamber it was fired from."

    This totally makes sense to me. I've only been hand loading for six months and the cases fired from our two AR-15's require quite a bit more trimming than cases from my 6.5x55 and .270.
  16. steve4102

    steve4102 Well-Known Member

    This is the main reason.

    You can find reference to this in this article.


    the bolt can unlock before the case has fully
    retracted from its expanded dimensions. We’re
    talking about milliseconds, but that’s all we have
    devoted to the entire process. The net result is that
    some amount of additional expansion frequently
    occurs in a case fired through an M14.
  17. 243winxb

    243winxb Well-Known Member

    Best to full length size for an M16A1

    Tried neck sizing for a M16A1. One magazine didnt like the fat bodies, slow feeding causing jams. IMR 4198 at maximum does not expand the brass as much as Nato ammo or high pressue loadings. You would need to FL size every other loading. With maximum full pressure loading, your going to have to FL size every time. Case life is the same when using a expander ball, FL or neck sizing dont matter. The necks go first.
    Last edited: Jan 3, 2014
  18. 243winxb

    243winxb Well-Known Member

    223 Full Length Resizing
    Not in an M16. The question is not about M14 rifles.
    Last edited: Jan 3, 2014
  19. steve4102

    steve4102 Well-Known Member

    It does in my AR-15's, my Mini-30. my Browning BAR's and my Mini-14. YMMV.

    ...and the slower the powder the more the increased expansion.
  20. Trent

    Trent Resident Wiseguy

    There's significant more lag time in the unlocking action of an AR-15, than there is a Mini-14, BAR, or M14 rifle. Unless you're doing something wrong (with powder), the bullet will be out of the muzzle before the round begins extraction. That isn't strictly true for the browning actions, the action is much more direct. (Ar15 bolt has to move quite a lot to unlock, that takes time; by the time it happens, that bullet is GONE and the gas pressure is vented)

    EDIT: Pistol length gas systems with high port pressure, 16" barrel, and fast burning powder, might make my above statement false, but they're the exception to the rule.

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