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Thread: Ammo headspace

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    Ammo headspace

    I think I understand the guages and their headspace measurement along with measuring of fired cases to get an idea of individual chamber headspace. Admittedly my googiefie is suspect, and I haven't spent much time looking, but on the unfired ammo itself, I cannot find "headspace" max/mins. Just distance of shoulder breaks from the base.

    Would someone please straighten me out and educate me as to the minimum headspace for unfired 223 and for 556 ammo? Thanks
    Last edited by triggerjerk; 02-18-24 at 19:51.

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    Ammo headspace

    Apologies for my post. Didn’t fully understand where OP was headed or asking…

    I’m understanding a lot from the dialogue. Thanks!

    Sent from my iPhone using Tapatalk
    Last edited by BuzzinSATX; 02-19-24 at 13:20.

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    Quote Originally Posted by triggerjerk View Post
    I think I understand the guages and their headspace measurement along with measuring of fired cases to get an idea of individual chamber headspace. Admittedly my googiefie is suspect, and I haven't spent much time looking, but on the unfired ammo itself, I cannot find "headspace" max/mins. Just distance of shoulder breaks from the base.

    Would someone please straighten me out and educate me as to the minimum headspace for unfired 223 and for 556 ammo? Thanks
    Most factory ammo is produced with the case being minimum dimensions. That is to say the cartridges are dimensioned is such a way that they should chamber and function in the vast majority of commercially produced .223/5.56 chambers.

    You can verify this with a case gauge, and you will find virtually all new cartridges will be flush with the “low step” of the headspace indication on the case gauge. Indicating their minimum length for safe headspace.

    If you’re feeding a semi-auto this is what you want because the minimum headspace loaded rounds ensure better feeding reliability.

    If you’re loading for a bolt action you can full length resize to set the shoulder back .002”-.003” from your fired case shoulder reading. So if you nominally have .006” worth of room to play with for a perfectly in the middle in spec chamber and your minimum headspace factory ammo grows .006” and then you resize the body and set the shoulder back another .002”-.003” you end up with a bit less clearance and less brass expansion. It might help accuracy a smidge too at the cost of not being able to run it in other chambers.

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    Coal Dragger's correct. Factory ammo is made to function properly in as many chambers as possible, so it's set to the minimum.

    Are you're setting headspace yourself on a bolt gun?

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    For bolt guns, I bump the shoulder back on fired brass .001-.002"

    Semi autos my require more, as much as .006" bump, as they tend to stretch quite a bit. I take new factory ammo, measure and fire it, then measure again. The difference is what I usually set the sizing die to bump.

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    Been using Redding extended shell holders to get head space of reloads within two or three thou of chamber headspace for my bolt guns for decades. I had quit using standard neck dies and went back to full length dies/ext holders because I could spin neck sized cases and see a greater lack of concentricity.

    Again, those cartridge diagrams show diameters and distances to breaks in the shoulders, but no one gives minimum headspace spec for ammo as a distance from the base to a datum point on the shoulder like it is specd for a chamber (min, max, OMG or go, no go, field). Obviously max ammo headspace needs to be just shorter than or right at the go gauge headspace. But what is the "minimum" ammo headspace spec in same units used for chamber headspace measurement? In another thread, mention of excessive headspace between ammo/chamber leading to problems was mentioned, and I realized I'd never run across minimum headspace spec for ammo, itself. If I'm not making sense, we can just let this thread go as I'm just curious and have had no problems so far (knock wood).... Know I do 'preciate ya'll.....

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    Quote Originally Posted by grizzman View Post
    Are you're setting headspace yourself on a bolt gun?
    Definitely. Not so much for .223, but 6.5, 308, and 300WM for sure. I get a decent amount of partial case separations in 6.5 because it's sized to run in 3-4 guns. Ideally you'd have a die and brass for each individual rifle, but our shooting is so disorganized, it's impossible to do things right.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

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    I reload "mostly" for Auto's and I want my rounds to work in any rifle I am shooting. I don't reload for specific rifles, I have too many for that to be a reasonable thing to attempt.

    I learned a long time ago, to check my brass after sizing with one of these. Pulling and re-re-sizing a hundred rounds isn't fun.

    Lyman Headspace / Case Length Gauge

    Tells me if my cases are sized correctly and that I have trimmed them to within spec.

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    In loading for "automatics", have y'all done any headspace/bullet seating measurements on factory and reloads before and after chambering to see what effect the "violence" of chambering has? I believe it also takes some math to determine actual bullet movement in the neck because of headspace change..... (And I don't have anything to measure runout with so haven't done that...)
    Last edited by triggerjerk; 02-19-24 at 11:52.

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    Quote Originally Posted by HKGuns View Post
    I reload "mostly" for Auto's and I want my rounds to work in any rifle I am shooting. I don't reload for specific rifles, I have too many for that to be a reasonable thing to attempt.

    I learned a long time ago, to check my brass after sizing with one of these. Pulling and re-re-sizing a hundred rounds isn't fun.

    Lyman Headspace / Case Length Gauge

    Tells me if my cases are sized correctly and that I have trimmed them to within spec.
    This ^^^

    I have both a Hornady cartridge gauge and the superior Sheridan Slotted Ammo Gauge. I use the Hornady for quick checks on all my reloads, and the Sheridan Slotted one to determine where the hang-up is, and then correct it.

    I could get by with just the better Sheridan, but I bought that one last.

    https://sheridanengineering.com/prod...unition-gauge/

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