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Thread: Head Space?

  1. #21
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    Where does that number come from? You may come across many that are very close but if you're pairing a new bolt with a barrel that has 15k+ rounds on it then it would be foolish to not check headspace. Considering the safety implications and the relative cost of a gage compared to 15k rounds of ammo it should be a no-brainer.

    Quote Originally Posted by HelloLarry View Post
    I wouldn't bother buying a headspace gauge for an AR. You can grab bolts from 5 different makers and there won't be more than 15 ten thous worth of difference between them.
    Quote Originally Posted by Shao View Post
    ...and if my 5.56 chamber is headspaced properly, will I need to gauge it for .223 as well??? No

    I'm also confused with all the go/no go/field/minimum designations on these gauges... Your bolt should not close on a field gage as it measures the maximum allowable headspace. Your bolt *should* close on a go gage. It may or may not close on a no-go gage because their dimensions are arbitrary and depend on what the user is trying to achieve. Go and no-go gages are used by gunsmiths and certain barrel makers when trying to reach an exact headspace for some kind of precision setup. The field gage is the only one to get if you feel the need. Make sure it is a real USGI field gage or find a way of verifying its dimensions.
    * For the same reason as no-go gages (Arbitrary dimensions).

    Last edited by Eric D.; 02-10-13 at 17:43.
    B.A.S. Mechanical Engineering Technology

  2. #22
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    Quote Originally Posted by Shao View Post
    OK... off to Brownells to get a headspace gauge... You've all convinced me...
    Shao, Iraqguns has a significant amount of experience inspecting ARs for proper dimensions and function. He told me that all that was needed to verify HS in this family of rifles was a proper field gauge. I told him that a minimum gauge was also required. IG expained that if the HS is too tight, it wouldn't chamber factory ammo correctly. He's right and this revelation made setting the headspace on the FALs I built easier.

    What I am suggesting, before the whole gauge thing gets blown out of proportion, that you PM IG and get his expert advice on checking your headspace and how to verify if the chamber is safe to use with 5.56 spec ammo
    Last edited by MistWolf; 02-10-13 at 18:10.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

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  3. #23
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    Quote Originally Posted by Ned Christiansen View Post
    The good news is that, in my experience at least, headspace is rarely wrong.

    Most manufacturers actually seem to take it seriously. I've always found it amazing all the things that are easy to get right, that they chronically get wrong. But in the case of headspace, which is, well, pretty critical and very easy to screw up, they almost universally get it right. I'm glad about that of course but still find it.... surprising.
    My buddy's SCAR-H is at FN right now because it had too much headspace which lead to part of the reciever cracking. Sort of funny that this thread came up actually. Good info so far.
    "Remember, if it doesn't violate the BYU Honor Code, it's not worth doing"
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  4. #24
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    O, I'll beat a dead horse since my fresh meat intake this week has been limited.

    Generally speaking, if you are using quality components (Noveske, BCM, Colt, DD, LMT I am missing a couple I am sure) then I would say it is probably not necessary to check the headspace if the parts are new. If they aren't new then I highly recommend checking it and following the procedures as outlined in TM 9-1005-319-23&P.

    The gages I use are the exact same ones as the U.S military uses. The only gage used in the M16 FOW is the "Field" gage.

    www.billricca.com has them. Bushmaster did have a true 5.56 field headspace gage on their site, although it didn't have the rebated rim, but I cannot find it any longer.

    Quote Originally Posted by MistWolf View Post
    Shao, Iraqguns a significant amount of experience inspecting ARs for proper dimensions and function. He told me that all that was needed to verify HS in this family of rifles was a proper field gauge. I told him that a minimum gauge was also required. IG expained that if the HS is too tight, it wouldn't chamber factory ammo correctly.

    What I am suggesting, before the whole gauge thing gets blown out of proportion, that you PM IG and get his expert advice on checking your headspace and how to verify if the chamber is safe to use with 5.56 spec ammo



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  5. #25
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    Quote Originally Posted by eperk View Post
    I did research on headspace when building my first weapon. My conclusion was if you buy a quality BCG and barrel there's not much to worry about.
    It helps to buy your BCG and barrel from the same company.
    Just my .02.
    Would everyone else agree with this, more or less? This was kind of my assumption after reading up on it here a few weeks ago also. Case in point, I have a brand new BCM BCG and will have a new BCM upper soon, I'd think they'd be fine together.
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  6. #26
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    For my sample of ten rifles, I have not had a rifle fail a Forster .223 field gauge yet using any combinations of the six Colt, BCM and DD bolts we have in the family. I am ordering the proper 5.56 gauge, though.

  7. #27
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    Quote Originally Posted by MistWolf View Post
    Headspace is...
    MistWolf, thank you, as your post was the most helpful and the first to answer my questions in a language I can understand. Honestly I think I needed that friggen circle with an x through it to understand exactly where on the shoulder all of this stuff was reliant on. Thank you!!!!

    Everyone else, thank you too, you have helped.

    With that said though I want to shift the focus a bit. I didn't post this topic in the AR General Discussions, it was moved here by the Mods (not questioning it, but I think after reading through everything I want to explain to you all a bit). I posted this in the New To Firearms forum because my question wasn't about Head Space in AR's and if my bolt will work in my new build, it was simply "what is head space"?

    And honestly the reason I asked was not related to AR's at all, it was related to my 30.30 which was passed down to me by my family and is my current hunting rifle. It's a very early late 60's Marlin, and it shoots really well but my question was after doing research and in relation to this thread I posted last week:

    https://www.m4carbine.net/showthread.php?t=123442

    Which deals with a reloading issue I had with this rifle, that after research and inspecting past cartridges suggests that there could be a headspace problem with this rifle that may have been there for a while but may be getting worse as I shoot it more.

    So my next question to all of you is in the case of a Lever Gun (Marlin 336), how would you correct an out of spec chamber with improper head space?

    I'm assuming a barrel swap is the only option...???
    Last edited by Mac5.56; 02-10-13 at 21:54.
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  8. #28
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    30-30 is a rimmed cartridge and they headspace the off the rim itself. I'm not too familiar with lever actions, but I would have a gunsmith inspect it, specifically looking at the bolt and locking lugs.

  9. #29
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    Yes, the 30-30 is a rimmed cartridge and the actual headspace is on the rim. The upside is, if the chamber is a little long or the cartridge is a little short, it's not a big problem and there is simple fix for the reloader.

    While the official headspacing of a rimmed cartridge is the rim, if it's a bottleneck case it can alternately be headspaced off a shoulder datum line. Savvy reloaders do just that to improve accuracy and case life.

    (Belted cartridges such as the 300 Winchester Magnum officially headspace off the belt. Again, knowledgeable reloaders set the resizing die so a bottle necked belted case will headspace on a point on the shoulder for accuracy. Doing so has the same affect- improves accuracy and case life.)

    A good gunsmith can accurately measure your chamber for you with the proper headspace gauges and/or making a Cerro-Safe casting.

    One simple solution is to shoot factory ammo in the rifle to fire form the brass, then adjust the resizing die so it sizes the neck without pushing the shoulder back. This method allows the reloader to make sure the cases match the headspacing of the rifle. It also means the cases may not fit another rifle of the same caliber
    Last edited by MistWolf; 02-11-13 at 08:29.
    INSIDE PLAN OF BOX
    1. ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
    2. MATCH SCRATCHES ON MATCH-BOX
    3. MATCH LIGHTS FUSE TO TNT
    4. BOOM!
    5. HA-HA!!

    -WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"

    http://i115.photobucket.com/albums/n289/SgtSongDog/AR%20Carbine/DSC_0114.jpg
    I am American

  10. #30
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    Thanks again MistWolf!

    Reloading has added a completely new element into this hobby for me, so much to learn! I appreciate you taking the time!
    Mobocracy is alive and well in America.*
    *Supporting Evidence for Hypothesis: The Internet
    -me

    'All of my firearms have 4 military features, a barrel, a trigger, a hammer, and a stock."
    -coworker

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