Headspacing with spent cartridge

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  • E.Shell

    Ultimate Member
    Feb 5, 2007
    10,243
    Mid-Merlind
    From what I am being told is that factory ammo is loaded short and designed primarily to be fired from an AR platform. Savage bolt actions are far more finicky.
    I guess it depends on what you mean by 'finicky'.

    An AR-15 should have plenty of room to close, so that you can never get it to fire out of battery. The bolt action Savage will close on a slightly oversize cartridge, and the bolt cams can size it down in the process. In this case, it looks like the AR is the finicky one.

    The firing pin protrusion specification for the AR-15/M-16 family of rifles is 0.028" to 0.036". The accepted firing pin protrusion for bolt guns is usually around 0.045" to 0.050". Given similar headspace dimensions, if your Savage cannot reach the primer, that AR cannot either. It would again appear that the AR-15 is the finicky one.

    Finicky in what way?

    I don't have facts this, but I'd bet your Savage also delivers a greater amount of force, due to the mass of the striker and design of the spring, but that's just speculation. Maybe Chad can chime in with spring weights and striker mass.

    Bottom line, ammunition should function and fire safely in a rifle that is headspaced within specs.
    I just measured a whole box and a vast majority are at 1.250" with a few as long as 1.253" I am measuring a couple more boxes and depending on findings, I will likely set headspace on a 1.250 round with 2 layers of scotch tape. This should give me a 0.003 bump +/- a thou. I will then see if a 1.255" measured round will chamber.
    Sounds workable and should get you through, but the problem is really the ammo if headspace is supposed to be 1.260".
    Then, when I get my reloading setup going, I will re-headspace on the 1.260 spec from a hopefully borrowed Go gauge.

    Sound plausible?
    I don't think I'd set it back to 1.260" if the factory ammo you might find yourself using might run as short as what you have now.
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,243
    Mid-Merlind
    Heaspace gauges for the .277 Wolverine are only $37 each from Pacific Tool and Die. OR, $99 for a set of 3 (GO, NO GO, FIELD).

    http://pacifictoolandgauge.com/wild...7-wolverine-headspace-gauges-new-release.html

    For $37 there is no reason not to get at least the GO Gauge (and for $74 to have the both Go and NO GO) and set a Savage barrel to minimal chamber. It's not like you're reaming a new chamber or need to turn down the barrel shoulder in a lathe. A barrel nut wrench is $27 from Midway USA or $15 rental from 4D Reamer Rentals.
    You can resell the gauges and wrench on fleebay or funbroker if you don't want to keep them.
    True. In fact, for something like setting up a new chamber, as you point out, just the "Go" gauge is enough.

    The problem the OP seems to have is that his rifle is right and the ammo is on the short side.
     

    4g64loser

    Bad influence
    Jan 18, 2007
    6,381
    maryland
    For 99 bucks, I'd buy the set of three gauges and keep em. I am a tool-hoarding fool. Even if I stop working with a particular chambering, I keep the tooling as it may come in handy later for something else, or I may get a wild hair and get back into the chambering. I have found that certain dies are handy to have around when forming cases or performing other sundry wildcatting tasks.

    buy the tooling, it won't be wasted money.
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    Heaspace gauges for the .277 Wolverine are only $37 each from Pacific Tool and Die. OR, $99 for a set of 3 (GO, NO GO, FIELD).

    http://pacifictoolandgauge.com/wild...7-wolverine-headspace-gauges-new-release.html

    For $37 there is no reason not to get at least the GO Gauge (and for $74 to have the both Go and NO GO) and set a Savage barrel to minimal chamber. It's not like you're reaming a new chamber or need to turn down the barrel shoulder in a lathe. A barrel nut wrench is $27 from Midway USA or $15 rental from 4D Reamer Rentals.
    You can resell the gauges and wrench on fleebay or funbroker if you don't want to keep them.

    I plan to do that very thing once I start loading my own ammo to the 1.260 spec, but in the meantime, the majority of the ammo I purchased is 1.250 - 1.255 and too short for the Savage finicky 0.001-0.003
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,243
    Mid-Merlind
    ...too short for the Savage finicky 0.001-0.003
    Cats are finicky.

    In logical, mechanical terms, please tell me exactly what makes the Savage "finicky"?

    Your continued use of this vague and seemingly inappropriate term really has my curiosity piqued and I would like to learn what is going on.

    With its camming power, the bolt action Savage can accept longer cartridges that approach exceed zero headspace, while the AR-15 would fail to lock up.

    The greater firing pin protrusion of the Savage can reach shorter cartridges that are out of reach for an AR-15.

    It really looks like your cartridges are up to 0.010" too short and you somehow seem to think they are just fine and your rifle is faulty, and that they would have fired in an AR-15 after failing in your "finicky" bolt gun.

    How is that even possible?

    I would like to help you get the bottom of this, but we have to deal in facts.

    ETA: IS your rifle faulty? Have you looked at firing pin protrusion?
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    Howdy Pinecone. We are talking about fine fitting to preserve hard-to-get brass and not just "safety", which is what those specs you quote revolve around, but anyway:The parent case is a .223 and resulting wildcats generally follow the parent case for this specification, if "specification" can be used with "wildcat". The difference between my .223 Go & No-Go is 0.003", due to the relatively short overall length of the case. This means that 0.0045" exceeds this acceptable range by 50%.Agreed. In a long 25-06, it wouldn't be a safety issue and is still between "Go" and "No-Go".Aye.Yeah, but again, these are for a different, longer cartridge and thus do not apply.

    Officially, the .25-06 uses the parent case's dimensions for headspace and these are as follows:
    "Go" - 1.940"
    "No-Go" - 1.946"
    "Field" - 1.950" (This 0.010" longer than minimum is considered the outer limits for safe use).

    The .223:
    "Go" - 1.464"
    "No-Go" - 1.467"
    "Field" - 1.470" (This 0.006" longer than minimum is max for safe use)

    So, if we flirt around with 0.0045", as measured by the Scotch Precision Tape Company, we are well beyond "No Go" and half way to "Field" before we fire our first shot.

    The first is why I posted the info about the match difference being 0.004".

    But your point about shorter cases having a smaller range makes sense.

    Do you know the difference in a Wilson case gauge for .223/5.56 between the flat and the indent of the end? I have one AR that needs the cases sized to fit all the way level with the lower surface. All my other .223/5.56 chamber rounds at the upper level fine.
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,243
    Mid-Merlind
    ...Do you know the difference in a Wilson case gauge for .223/5.56 between the flat and the indent of the end?
    No, I don't specifically know and mine are in storage ATM.

    The SAAMI drawing of the .223 cartridge shows the distance to the datum line as 1.4666" -0.007", so if the case gauge correctly shows min/max headspace, the difference should be about 0.007".

    I have one AR that needs the cases sized to fit all the way level with the lower surface. All my other .223/5.56 chamber rounds at the upper level fine.
    This is Clandestine's forte`, but it sounds like something is out of spec. You could change bolts to see if the condition changes. If swapping bolts makes it correct, you'd have a bolt out of spec. If swapping bolts doesn't help, the barrel extension is out.

    If the bolt turns out to be the issue, the ejector might be compressing the spring to solid and not going flush, causing the ejector to protrude enough to resist chambering a round.
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    I used the word finicky because that is the word used by the cartridge developer. He also said "savage rifles need the ammo to be minimum bump".

    Originally, fired rounds measured 1.260" (in spec) but as a vast majority of factory loaded ammo was 1.245" to 1.255", with about half being 1.250" and the firing pin protrusion being 0.054" - I was getting light strikes and no detonation. I was also told that the ammo was primed with CCI 450 primers which are apparently harder than CCI 400 primers that are recommended for those using Savage rifles.

    So.....my questions are this: Should I reset the headspace to the correct spec of 1.260" and just extend the firing pin until it detonates the shorter rounds? Would the bump gap of 0.005 - 0.010 affect accuracy? Would the extended firing pin pose possible risks of puncturing the cap of the closer to spec rounds? Risk(s) of this?

    I want to try and have this rifle ready and sighted in for deer season and want it to be as accurate as possible.
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,243
    Mid-Merlind
    I used the word finicky because that is the word used by the cartridge developer. He also said "savage rifles need the ammo to be minimum bump".
    Thank you.

    I really don't know what to say to your ammunition supplier's claims. That I say I disagree indicates a mere difference of opinion, but then there are these pesky facts... Let's just pull it apart and you can decide.

    I would suggest you forget this 'finicky' word in the context of precision machinery, and look for logic in all things. I will tell you in no uncertain terms that I have had hundreds of Savage rifles on my bench and in front of my spotting scope and I have not seen even one that I would call finicky. They are workhorses and quite robust. They lock up solidly and are quite reliable.

    Above, I have given you two very easily proved, very easily illustrated examples of why a Savage is definitely not finicky with ammo compared to an AR-15. There is really NO other factor that contributes either way to this issue. If the ammo is in spec, both rifles should fire it safely if they too are in spec.

    If the ammo is not in spec, the AR will be/would have been the first to choke, plain and simple. If the ammo came in too long, the AR is prone to not locking up and will either not fire, or fire not fully in battery. If the ammo comes in too short, the AR's shorter protrusion is the first one NOT to reach the primer. Clearly, truth be told, if the ammo doesn't work in your Savage, there is no hope of it working in an AR-15 that was also chambered to spec.

    Regarding the "minimum bump" requirement: If you get a chance to read the article I linked you to above, I mention a clearance range of 0.0015" to 0.002" for headspacing match ammo. We do this for two reasons: Better fit can mean better precision, and, less shoulder movement means less stretch, trimming and case loss. Any tighter, we get function issues, and more clearance, we start prematurely stretching cases. But this is a special case for special applications and not factory guns with factory ammunition.

    Headspace gauges are set up to give you absolute minimum and absolute maximum and with the .223 class of cases, it's a 0.003" initial tolerance, so there's no way to say a Savage rifle has to be fitted with any certain headspace range less than that. If the ammo is in spec, the Savage will reliably and safely fire it.

    Regular ammo can vary widely from this precision fit condition, but because it is fired once, we can stretch hell out of it and not pay the consequences...until we reload it.

    That your firing pin cannot even reach some cartridges is a clear signal that we are beyond safe headspace limits, and I realize you recognized this early on when you made your original post.

    In one of your posts above, you mention that the correct headspace length is 1.260". I found JGS "Go" gauge drawing showing a median headspace dimension of 1.270" +/-.005 at the https://www.thefirearmblog.com/blog/2017/04/28/277-wolverine-cartridge-now-public-domain/, and I also found the reamer drawing that shows the cutting edge to run to 1.265". Both drawings bear the name of the designer, so it seems like 1.265" is the target number for the rifle headspace. Since this is a "Go" gauge, it represents the minimum chamber dimension.

    When you measure a fired case with respect to headspace, two often unexpected things happen:

    First, the case expands to fit the chamber and forms a close fit, but then, it springs back a couple thousandths and releases the chamber so you can extract it. When a cartridge case sticks in the chamber due to a high pressure load, you are seeing the effects of the brass NOT springing back.

    Then, if we are working with a small and/or gently sloped shoulder and/or soft brass, we sometimes distort the brass slightly during measurement, further shortening our apparent measurement.

    If your rifle was correctly headspaced when the barrel was installed, it would have been around 1.265" and I'd bet your 1.260" brass was fired in a slightly larger chamber than it measures. You may be able to control your measurement technique, but you cannot control springback.
    Originally, fired rounds measured 1.260" (in spec) but as a vast majority of factory loaded ammo was 1.245" to 1.255", with about half being 1.250" and the firing pin protrusion being 0.054" - I was getting light strikes and no detonation.
    This is because the ammo is completely outside safe tolerances for headspace. Even a long action cartridge gives you 0.010", but we're even past that, The .223 gives you 0.006" and we are DOUBLE that.

    Unless we can uncover some way in which your measurement technique is giving you bad numbers, it is increasingly clear that the ammo is not loaded to spec, perhaps even to a point of being beyond industry accepted safe limits. To not acknowledge this and to further say it won't shoot because the rifle is a Savage is incredulous. To also say it would shoot OK in a correctly chambered AR-15 is also beyond belief. How can these stories be true?
    I was also told that the ammo was primed with CCI 450 primers which are apparently harder than CCI 400 primers that are recommended for those using Savage rifles.
    This is a bit backwards, and also thin. The "standard" rifle primer, in any brand, is pretty much standard for all handloading for all rifles. It is used in almost every application, except for a very few specific situations. The main use for the magnum primers is when we work with magnum cartridges and their larger quantities of harder-to-light powder.

    The magnum primer's harder cup makes it more resistant to slam fires, so it is often substituted in self loading rifles, even when the increased brisance isn't needed. So in actuality, the magnum primer is the aberration. CCI makes a specific primer for this self-loader application, their #41 (small rifle) and the #34 (large rifle), and I'm surprised they're not using it.

    Be that as it may, your Savage will decisively detonate not only your small rifle magnum primers, but also large rifle magnum primers. It won't care and dents will be as deep as they would be in standard primers. If you mash an ant with a size 10 shoe, does the ant care if you weight 160 or 180? That's about the difference that primer cup is to that 25# spring focused into about 0.007 square inches of firing pin tip.

    If you change calibers in the Savage, we change the bolt head (to match the case head), bolt stop (to set the correct stroke) and magazine guts (match cartridge length). No other parts are swapped out. This means that the same old firing pin and spring, the striker assembly must cope with any cartridge you put in it, or, more properly, the striker assembly MUST fire any primer. Large Rifle, Small Rifle Magnum, Small Rifle, Large Rifle Magnum, #34, #41...nothing special, all in a days work.

    Bottom line: Blaming the primer is a non-starter, and the only reason one might care at all is if trying to duplicate the load.
    So.....my questions are this: Should I reset the headspace to the correct spec of 1.260" and just extend the firing pin until it detonates the shorter rounds?
    No, I would not want to see you do that, because if you fire one at 1.245" in your 1.260"+/- chamber, it may stretch far enough to fail. Failure will possibly dump a shitload of gas and brass into your world. In fact, were it mine, I'd want protrusion someplace back between 0.045" and 0.050", which will be plenty when headspace is right.
    Would the bump gap of 0.005 - 0.010 affect accuracy?
    Accuracy would be unaffected up close, where the velocity swings inherent to ignition problems would not show. Longer ranges would begin to sort out your erratic ignition, with fast ones landing high and slow ones landing low.
    Would the extended firing pin pose possible risks of puncturing the cap of the closer to spec rounds? Risk(s) of this?
    Yes, there is greater risk of puncturing the cup with a too long protrusion, although this is not as dangerous as separating a case head. You just get to ruin the tip of your firing pin with the hot gas.
    I want to try and have this rifle ready and sighted in for deer season and want it to be as accurate as possible.
    I understand.

    Going out on a limb here, I'd say the ammo is defective, below headspace guidelines, someplace between unreliable and unsafe. I would want the maker to swap it out for functional ammo, with no more fairy tales about how it's you rifle's fault. This is quite easily demonstrated when you can document cartridge headspace measurements that exceed customary limits among cartridges from the same box.

    Barring replacement, we should try to make safe use of it so you can get going.

    I would go back to the post I made above about finding the longest rounds and setting your rifle to just chamber on those. At this point, I would probably sort through all available ammo and see what's there.

    If everything is someplace between 1.245" and 1.255" except for a few, then I would set those few aside and work with one length group. I would then forget further measurement and just work with the longest of your working rounds, Adjust your barrel to where you can just 'feel' the cartridge when the bolt goes into battery, then tighten down the nut. Go to the range with it and get zeroed. If you experience any difficulty in chambering, give the barrel a tiny bit of a turn out, then double check your zero.

    This should give you a graceful and safe solution to using up that ammo and get you hunting.

    When you get ready to reload, you may or may not be able to fully utilize that brass unless your die will go down to 0.010" undersize. Most will just take it to zero, but Redding makes shellholders that will allow you to size a little more than that.

    If you want to use those original, short cases, but return the rifle to spec, I would suggest fireforming them to blow the shoulder out, vs shooting them short and letting them stretch at the web.

    ETA: Do not shoot your rifle indoors.
     

    babalou

    Ultimate Member
    MDS Supporter
    Aug 12, 2013
    16,016
    Glenelg
    Wd Zachary

    For 99 bucks, I'd buy the set of three gauges and keep em. I am a tool-hoarding fool. Even if I stop working with a particular chambering, I keep the tooling as it may come in handy later for something else, or I may get a wild hair and get back into the chambering. I have found that certain dies are handy to have around when forming cases or performing other sundry wildcatting tasks.

    buy the tooling, it won't be wasted money.

    Did that for a 22 Nosler build in Chad’s class
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    Is there a tool I can use to test length without chambering and shooting? I tried using a 1.255" round and wound up with a spent cartridge at 1.245" So apparently my "feel" of turning the action on to the barrel is faulty.
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    What do you think of me trying this?

    I ordered a GO Gauge. Install gauge and tighten action to barrel. Make a mark with a thin paint pen. Then add two layers of scotch tape to the GO Gauge (0.005") and repeat process. This will give me a known distance. Remove gauge and tighten action to barrel the known distance beyond the first mark and tighten. This should give me the 0.005" closer distance than the gauge alone. Test and measure.

    Plausible? (I guessing here)
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    No, I don't specifically know and mine are in storage ATM.

    The SAAMI drawing of the .223 cartridge shows the distance to the datum line as 1.4666" -0.007", so if the case gauge correctly shows min/max headspace, the difference should be about 0.007".

    This is Clandestine's forte`, but it sounds like something is out of spec. You could change bolts to see if the condition changes. If swapping bolts makes it correct, you'd have a bolt out of spec. If swapping bolts doesn't help, the barrel extension is out.

    If the bolt turns out to be the issue, the ejector might be compressing the spring to solid and not going flush, causing the ejector to protrude enough to resist chambering a round.

    I am out of the country, so can't measure mine.

    Already planning to take it to him. It think it is just a min spec chamber. Factory ammo is fine, as is reloads sized to the min spec with the case gauge.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    The magnum primer's harder cup makes it more resistant to slam fires, so it is often substituted in self loading rifles, even when the increased brisance isn't needed. So in actuality, the magnum primer is the aberration. CCI makes a specific primer for this self-loader application, their #41 (small rifle) and the #34 (large rifle), and I'm surprised they're not using it.

    The CCI 450 (Magnum) and #41 (military) primers are almost the same.

    They use the same cup (thickness and hardness) and the same amount of the same priming compound. The #41 has a bit more space between the cup and the anvil.

    Using a CCI #450 instead of a #41 is not a huge difference, even with regarding slam fires.
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    Isn't the barrel threading a known pitch. 20 tpi maybe? So if you think you're 0.010" tight, unscrew it 0.20 turns or 72 degrees? Maybe start with a smaller increment.
     

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