Explaining Headspace

Discussion in 'The Ammo & Reloading Forum' started by Insulation Tim, Jun 6, 2010.

  1. Alpo

    Alpo Well-Known Member

    Feb 3, 2007
    NW Florida
    You've got a half-inch difference in the length of your brass? I think you typed some numbers wrong.

    First, ignore that comment about "if you shoot a lever, don't full-length resize". That's nonsense. You can get away with neck-sizing on a bolt gun or a single-shot, but anything else needs full-length resized.

    Second, you can only get away with neck-sizing if it is going to be shot in the SAME GUN. If you have ONE 308 bolt gun, and you fire new shells in THAT 308 bolt gun, then the brass is fire-formed to THAT chamber. You can then neck-size the brass that will be loaded to be fired in THAT gun. There is no other gun in the world that has that exact size chamber. NONE. NOWHERE. So if you neck-size brass shot in THAT 308 bolt gun, and then try to put the loaded ammo into THIS 308 bolt gun, there is a good chance that it will not fit.

    Now, as I understand your post, the brass you have is stuff fired in YOUR gun, stuff fired in YOUR WIFE'S gun, and stuff that has been given to you or that you found at the range. In other words, NOT ALL FIRED IN THE SAME BOLT GUN OR SINGLE SHOT. It needs full-length resized.

    Once it has been full length resized, it will fit in any gun of that caliber. If you plan to neck-size after that original full-length sizing, definitely keep your brass separated from your wife's brass.

    If your gun is NOT a bolt or a single-shot. If it is a lever, a pump or an automatic, ignore anything anyone tells you about the joys of neck-sizing. It will just cause you pain and heartache, trying to make it work.
  2. oneidapj

    oneidapj New Member

    Sep 2, 2012
    Thanks Alpo,

    My mistake at just learning to read my dial caliper... the lengths range from2.484 to 2.500.

    Yes the brass I have is from different guns but nothing from the range, don't want to risk getting bad stuff. So what I planned to do was tumble the brass, run it into the die to full-length resize, decap it, inside neck expand, trim all brass to same length (if I need to crimp them) or at least trim them to the spec of 2.494 that the Nosler book says (if I don't need to crimp them), tumble again, prime, powder charge, bullet seat.

    Maybe there is something I am totally not understanding. OK.... Full length resizing means returning the brass to the original new brass size, except for overall length. And neck-sizing just spreads neck big enough to accept and hold the bullet. Nooowww, doesn't the neck-expanding part of the die open every case to the exact same diameter? So why would do you say that if I plan to neck-size after the full-length sizing keep our brass seperate?

    From what I have read so far about crimping... I don't need to crimp.? Maybe I should put a light crimp on the rounds we are going to actually pack around hunting. But if I do that,shouldn't lightly crimp them all to make it all all the more consistant?

  3. Alpo

    Alpo Well-Known Member

    Feb 3, 2007
    NW Florida
    No, neck sizing is squeezing the neck down.

    Your bullet is .308. The diameter of the bullet-section of the chamber of your rifle is gonna be something like .350. Let's say your brass is .015 thick. That means you got a 308 bullet with 015 on each side of it, making a total of 338 diameter. There must be some room for the brass to expand to release the bullet. so let's say that the bullet section of your chamber is 350.

    You fire the gun, the case expands until it hits the chamber walls and the released bullet goes downrange. Now your fired case has a neck OD of .350, and since the walls are .015, the ID is .320. You put a 308 bullet in that 320 neck and it will fall back out.

    So you need to squeeze the neck down, so that the ID is about 306, so when you shove that 308 bullet in there the neck holds it tightly.

    The case body, which started at .441, has expanded to .460. The shoulder, which started at 1.948 is now at 1.953. It is now "fire-formed" to fit the chamber of THAT gun. When you full-length resize a case, it squeezes the body back down to .441 and pushes the shoulder back to 1.948, along with squeezing the neck do to an ID of .306.

    When you neck-size, it does nothing to the body or the shoulder of the case.
    All it does is size the neck back down to that 306 ID.

    A cartridge that is loaded into a case that has been full-length resized will fit into any 30/06 rifle.

    A cartridge at has been neck-sized will only fit easily into the gun it was fire-formed in.
  4. Alpo

    Alpo Well-Known Member

    Feb 3, 2007
    NW Florida
    In reloading, "sizing" always means "squeezing smaller". It's short for "resizing". Making the neck of the bullet big enough to accept the bullet is "expanding". First you "size" it, which makes it undersize, and then you "expand" it, which makes it big enough.
  5. oneidapj

    oneidapj New Member

    Sep 2, 2012
    I'm trying to grasp this with what I want to do.

    What are your thoughts of crimping these bullets that I bought, or not? Basicaly we are going to be doing a bunch of target shots, but with intent of a good hunting kill shot.
  6. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA

    For a bolt gun crimping is not necessary if the neck tension is tight enough to securely hold the bullet in the case with normal handling. For good brass and good bullets that is always the case. For any gun that has really heavy recoil, is lever or pump operated or semi-auto you should crimp. Crimping hunting ammo might be a good thing to do as extra ammo is often carried loosely in the pockets.

    For rifle cartridges there are two ways to crimp but the cases must be all trimmed to the same length (AFTER SIZING!!!) for the first method.

    1). The seating die comes with a crimping ring up inside the die and is engaged by adjusting the die down in the press. The end of the case hits that ring and folds against the bullet. You must be careful to not over crimp as you will collapse the wall of the body of the case or expand that area of the crimp such that it will not fit into the chamber. There are dimensions in the reloading manual and the neck must never exceed those limits in the area of the crimp.A collapsed wall of the body of the case may also not fit into the gun's chamber. A little crimp is better than none.

    2). LEE makes a rifle only Factory Crimp Die (FCD) that works on a completely different principal and is a much better way to go. The die is a separate die for crimping only. It has a collet that closes on the end of the neck to push the end of the neck horizontal into the bullet in about four discrete places around the neck of the case. While the cases must be trimmed there is a greater variation allowed as long as none exceed the max case length listed in the manuals. You can over do this too and distort the bullet but a little crimp is better than none.

    For ammo that I must crimp (heavy recoil ammo, lever or pump gun ammo or semi-auto ammo), I use the LEE FCD exclusively if I can get it for the caliber of choice.

    In your case the bottom line is crimp your hunting ammo and forget about crimping target ammo.

    Last edited: Sep 4, 2012
  7. oneidapj

    oneidapj New Member

    Sep 2, 2012
    Okay, think I got it. Just have to get a case lube pad and a case trimmer and then I can get started. Thank you very much.
  8. bluesea112

    bluesea112 Active Member

    Nov 20, 2005
    West, TX
    Crimping = better accuracy and consistency. (tighter groups)
  9. lcn

    lcn Active Member

    Apr 11, 2013
    Washington State
    New here. Just been looking around. Been casting bullets and reloading for over 50 years. Rifles, pistols and shotguns. I am impressed. You guys rock. The explanation of headspacing was better than very good by all. For the newbees here you can't go wrong, listen up. These guys know what they are talking about.
  10. woolleyworm

    woolleyworm Well-Known Member

    Feb 23, 2009
    SW Fort Worth

    Welcome to TFF lcn ! I grew up in Darrington and have family all around you. I sure don't miss the cold though, alot more nice shooting days down here in TX.

    I do miss the size of the muleys though.;)

    Glad you enjoyed the headspace thread and appreciate your comments.

    Semper Fi,

  11. BlackEagle

    BlackEagle Well-Known Member Supporting Member

    Nov 25, 2011
    Welcome to TFF, Icn. There is a host of experience and shooting wisdom on these forum pages, and people here are glad to share their wisdom and experience with newcomers. Glad to have you aboard and hope to hear from you.
  12. Spiritman

    Spiritman New Member

    Oct 20, 2013
    Cypress, Texas
    I have a .357 Mag Revolver and have been reloading 180-grain cartridges for several years. Recently I purchased a Henry .357 magnum lever action rifle. Will the headspace matter if I shoot the revolver rounds out of my rifle? The salesman at Gander Mnt said that I could shoot the same ammo out of both, but this thread on headspace is making me stop and wonder if there is a different cartridge headspace for a revolver and a rifle.
  13. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    Headspace is the distance from the bolt face to the reference point on the cartridge. Rimmed cartridges like 357MAG headspace on the front edge of the rim All 357 MAG chambers should be using the same measurement for that cartridge. 357 MAG revolver ammo should fit 357 rifles with NO problem and vice versa if the ammo is made to the specs in reloading manuals or the ammo industry standards for ammo

    Any rifle or pistol marked for the same cartridge should be able to interchange ammo if the ammo is made to the standards for ammo and chambers set up by the organization SAMMI, the industry wide organization that all manufacturers follow.

    Last edited: Oct 28, 2013
  14. Alpo

    Alpo Well-Known Member

    Feb 3, 2007
    NW Florida
    The only problem I can see with shooting 180 grain 357s through a lever gun is the length. Standard 357 bullet is a 158. 180 is actually a 35 Remington rifle bullet.

    Using that large of a bullet, the overall length of your cartridge might - MIGHT - cause feeding difficulties coming from the magazine to the chamber.

    Some - SOME - 357 rifles do not like 38 special ammo because it is too short, and the gun does not like to feed it. There are lots of discussions on cowboy boards about seating bullet long in 38 brass, so they will feed in their 357 rifles.

    Logic says that if being TOO SHORT can cause feeding problems, so can being TOO LONG.

    Might not have a problem. Your gun might eat 'em up like jellybeans. But it might not. Only way to know is try.

    But no, as LD said, there is no headspace problem.

    RODANTKING New Member

    Oct 18, 2013
    I just read though this tread. I also already read the honady manual which I thought did a very good job of explaining it. I thought I understood it until I took a closer inspection of my new glock. I have never owned one before but I shot at least 20 of them and to my memory they all have the part I'm going to refer to. I pretty sure glock is going to call it there loaded chamber indicator. I was never sure why they but it on there because it is not very effective (not that I ever cared). After closer inspection it hooks into the rim of the case. Is these tiny part trying to control head space or is it spaced of the mouth like any other strait walled rimless case?
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