Headspacing with spent cartridge

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  • balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    I have a Savage Model 12 with a wildcat barrel installed. Took it to the range for its maiden voyage and was having multiple light primer strikes. After using a comparator between a factory round and a spent casing, the difference was 0.013, which tells me I have a headspace problem.

    As this is a wildcat, a Go gauge is expensive and rather difficult/time consuming to come by. I have been told and read on a few pages that you can take a spent case, apply a single layer of scotch tape (which has a thickness of 0.0025" thick), insert into the chamber and run the action onto the barrel until it just touches and then tighten the barrel nut back up and it should be GTG.

    Has anyone else heard of or done this?
     

    bigjohn

    Ultimate Member
    Jun 29, 2007
    2,752
    I’ve heard about it. They named scotch brand because it was consistent. More of a make shift head space
     

    Shazam

    Active Member
    Dec 20, 2012
    731
    Although it's not the best, correct, or probably even an acceptable way to do it, people have checked or set headspace with an unfired cartridge and tape. However, a spent cartridge has expanded to fill the chamber that it was fired in and cannot be used for this purpose.
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,244
    Mid-Merlind
    As a wildcat, don't you have the luxury of simply adjusting your die to the chamber and leave it at that? Certainly you're not re-headspacing a rifle to match a die setting....are you?

    Even when loading for a standard cartridge, the die can create an excess headspace condition. The manufacturer's "boiler plate" die setting instructions are not usually optimum for anything but the absolute SAAMI minimum chamber.
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    As a wildcat, don't you have the luxury of simply adjusting your die to the chamber and leave it at that? Certainly you're not re-headspacing a rifle to match a die setting....are you?

    Even when loading for a standard cartridge, the die can create an excess headspace condition. The manufacturer's "boiler plate" die setting instructions are not usually optimum for anything but the absolute SAAMI minimum chamber.

    The ammo I have was manufactured by someone else that loads for this caliber. I have not started loading my own yet and likely will not be set up to load for several months yet.
     

    4g64loser

    Bad influence
    Jan 18, 2007
    6,381
    maryland
    just out of idle curiosity, what is the wildcat? Someone here may have a headspace guage set and might be able to help you out. I have a couple wildcats myself. The only one I don't own gauges for, I don't have to worry about as the chamber was cut precisely to spec and the dies were made exactly to match. That barrel is also shouldered and thus not adjustable.

    If you do plan to "set" your own headspace on a nut type installation, I would not use a fired case. As Ed says, that is going to make a bad situation worse. You would need to use an unfired case with either scotch tape or packing tape on the case head. strip the bolt head of ejector and extractor when performing these operations.
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    just out of idle curiosity, what is the wildcat? Someone here may have a headspace guage set and might be able to help you out. I have a couple wildcats myself. The only one I don't own gauges for, I don't have to worry about as the chamber was cut precisely to spec and the dies were made exactly to match. That barrel is also shouldered and thus not adjustable.

    If you do plan to "set" your own headspace on a nut type installation, I would not use a fired case. As Ed says, that is going to make a bad situation worse. You would need to use an unfired case with either scotch tape or packing tape on the case head. strip the bolt head of ejector and extractor when performing these operations.

    .277 Wolverine

    Just had a chat with the developer. He says the loaded ammo is designed to headspace with an AR and Savage rifles need minimal headspace. He recommended around 0.003" and said I should use 2 pieces of scotch tape on an unfired cartridge and screw down until it firmly seats against the round as 2 pieces of tape is 0.0045".

    I had removed the ejector, but left in the extractor to hold the round in place. Would this affect the end result?
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,244
    Mid-Merlind
    I honestly think you're backing into this and doing it the hard way. I really want to say "wrong way", but maybe that's a bit strong.

    First off, .0045" is nothing near "minimum" headspace and the person yoiu spoke with should know this. You are going to create case head separations with very few firings if you maintain such a large clearance. "Minimum" headspace is something like .0015" to .002" - just enough to chamber smoothly, even with a little fouling.

    Ammunition headspace requirements are either a) no different from one rifle to the next, or, b) in practice, slightly greater clearance for the AR-15, which depends on spring tension to go fully into battery. There is NO headspace spec that applies only to Savages and ARs and not to everything else.

    Do you suspect your rifle to be faulty? Was the barrel installed by someone who didn't know what they were doing? If so, then it might make sense to match your friend's rifle (not necessarily his ammo).

    What is the headspace dimension with this ammo in your friend's rifle? His ammo may also be marginally short in his own gun, just not quite short enough to misfire.

    Is your friend supplying all of your ammo, or just enough to get you out to the range once or twice? Otherwise, setting up your rifle to match your friend's die setting, which is still not necessarily right, even for his own rifle, doesn't make sense at any level, unless he is providing you with all of your ammunition.

    Wildcats, especially, and even factory-supported cartridges, can and will vary from what we would call "minimum" to what would be "maximum". If your rifle is correct and his is too tight, or if his dies are set to provide too much shoulder setback, you will be maladjusting your rifle. The good news is that wildcats are loaded to individual rifles and your maladjusted rifle won't come to a point of failing to chamber a corrected configured factory round.

    In teaching the precision handloading classes, I very often see dies, even for factory ammo, set to deliver too much shoulder setback. This usually comes from setting the dies to the manufacturer's generic, cover-my-own-butt directions. These directions are intended to provide minimum length ammo so that it will chamber smoothly, even in an SAAMI minimum chamber. Minimum length ammo is seldom what is actually needed for any given rifle, and VERY few rifles are ever set to minimum, except custom match rifles. Most custom match rifles are very close to minimum and this is about the only place the die maker's directions will deliver well-fitted cases.

    Setting your own dies for a wildcat or factory cartridge is very straightforward, especially with the .277, because the shoulder of the parent case gets set back. Were this my rifle, I would disregard your friend's ammo and load my own from the beginning, tailored to fit my own rifle. Set you sizing die to be just up off the shelholder, so you are still not sizing enough to chamber. Use a fresh .223 case, run it into your sizing die, cut it off as required, and try to chamber it. If it won't chamber, good. Adjust your die in about 1/4 turn at a time, test fit and try it in the chamber until you get it to chamber freely. Grab another new case and size that one once with your new die setting and make sure it works. At this point, I would make tiny die adjustments until I found the exact "zero" headspace point, then plan for about .002" clearance.

    Maybe this will be of help:
    http://www.shell-central.com/Brass_Prep1.html
    I suspect your ammo is going to want to be at about a "Level 2" fit.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    I just looked, and found several references to the difference between a Go and a No-Go for .20-06 to be 0.004 inches.

    So 0.0045" is not excessive. 0.045" would be HUGE.

    Another site states the benchrest/match gauges are about 0.004" and regular gauges at 0.006"-0.008".

    Another one states that the SAAMI spec for the difference between Go and No-Go is 0.0035".
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,244
    Mid-Merlind
    OK...the information above is a little unclear and I have misunderstood the situation. Very sorry.

    So your friend's loads are not his own handloads to fit his rifle, but instead, your friend loads commercial factory ammo for this wildcat. This changes this quite a bit and now I understand why you said "factory loads" AND "my friend's loads" above.

    Then yes, do adjust your rifle to barely accept his loaded factory rounds, NOT cases fired in another rifle. Why introduce that extra 'unknown'?

    No way I would use two layers of tape, though, and I stand by what I said above about 0.0045" killing your brass. I am especially sensitive to killing brass when it is something that is hard to get and/or hard to make.

    I have headspaced my own bolt action match rifles to barely accept factory match ammo, which means that it will barely or even not quite swallow a "Go" gauge. This is admittedly tight, but these rifles have lapped & lubed lugs, typically use only that one type of ammo and no lives are at stake. If you want "generous" clearance, more appropriate to a multi-purpose rifle, then just the one layer of tape would give you that.

    If you wanted a more precise and smaller measurements, use a small piece of shim stock of desired thickness, held in place with a small dab of grease. If you put a dot of grease on the case head, then press the shim stock on and twist/grind it in, the grease will hold it in place long enough for measurement without contributing substantial thickness.

    If you get unexpected flattening of primers (edges) without cratering, your headspace is probably still a little long.

    Headspace dimensions will creep up a little with use and wear. Fine aberrations in the chamber get smoothed out, un-lapped locking lugs mate, barrel threads seat, things stretch out and these tiny factors add up to a couple thousandths over time. Starting at minimum ensures that you won't eventually creep out to or past maximum. Having a bolt action, you will not have difficulty with lockup if you encounter a slightly tight cartridge.

    The CCI-450 is the small rifle "magnum" version and will provide greater brisance to help ignite larger charges of powder using thicker deterrent coatings uniformly. It also has a slightly harder cup. The harder cup resists slam-fires better, so he also may have concerns with that due to the AR-15 application.

    The harder cup vs reliable ignition is a non-issue in a rifle with a healthy firing pin spring and correct headspace. Your Savage striker assembly, for example, is used with all combinations of bolt heads and for magnum/non-magnum cartridges. It should have no issues at all with magnum primers, IF it can reach them.

    I would suggest that when you do begin loading on your own, that the CCI-450 is a bit much for the capacity and powder types found in the .277. I have seen magnum primers produce erratic pressures and wide velocity deviations in cartridges that don't need them. You're unlikely to experience a slam fire in your bolt gun, so the harder cup is of no benefit.
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,733
    Socialist State of Maryland
    As a wildcat, don't you have the luxury of simply adjusting your die to the chamber and leave it at that? Certainly you're not re-headspacing a rifle to match a die setting....are you?

    Even when loading for a standard cartridge, the die can create an excess headspace condition. The manufacturer's "boiler plate" die setting instructions are not usually optimum for anything but the absolute SAAMI minimum chamber.

    This. ;)
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    I think I may have found the issue...

    The developer says the shoulder, using a comparator, should measure 1.260" - I measured unfired ammo and I am getting 1.258-1.260" - I measure ammo that did fire and am getting 1.260-1.263"

    Now, when I measure ammo with the light primer strikes, they are almost all measuring at 1.250"
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,244
    Mid-Merlind
    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:
    I just looked, and found several references to the difference between a Go and a No-Go for .20-06 to be 0.004 inches.
    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%.
    So 0.0045" is not excessive.
    Agreed. In a long 25-06, it wouldn't be a safety issue and is still between "Go" and "No-Go".
    0.045" would be HUGE.
    Aye.
    Another site states the benchrest/match gauges are about 0.004" and regular gauges at 0.006"-0.008".

    Another one states that the SAAMI spec for the difference between Go and No-Go is 0.0035".
    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.
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,244
    Mid-Merlind
    I think I may have found the issue...

    The developer says the shoulder, using a comparator, should measure 1.260" - I measured unfired ammo and I am getting 1.258-1.260" - I measure ammo that did fire and am getting 1.260-1.263"

    Now, when I measure ammo with the light primer strikes, they are almost all measuring at 1.250"
    Yup.

    I'd take the compaator to a box of ammo and find the longest one, then set my barrel to just clear it.
     

    E.Shell

    Ultimate Member
    Feb 5, 2007
    10,244
    Mid-Merlind
    But what about the shorter ones? Would accuracy be affected by the 0.0010 difference?
    You don't want the headspace so tight that all of your factory rounds will not chamber, thus the logic of using the longest (worst case) one.

    I would be very surprised that factory ammo that hasn't been cycled through the rifle varies as much as 0.010" and your testing of unfired ammo straight from the box seems to prove that out. The ones that didn't fire were either modified by cycling through the gun or your measurements aren't reliable or they are defective from the factory and your rifle weeded them out.

    I would lean toward finding a way to ensure measurements are taken in such a way that if any burrs or formed-shoulder irregularities are present, you're not picking up a 'before' and 'after' being smoothed out by the gun. Try measuring a few and then cycling them through (don't shoot your rifle indoors :D), then remeasuring.

    If the short ones are not a product of mismeasurement or modification through the rifle, I'd send them back.
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    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 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.

    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?
     

    balttigger

    Ultimate Member
    Oct 15, 2008
    3,051
    Middle River, MD
    Tried to headspace on a 1.255" round and wound up at 1.245" AUGGHHH!!

    Oh well, gotta get some sleep and work 12hr shifts this week then hunting. Try again next week I guess...
     

    K-43

    West of Morning Side
    Oct 20, 2010
    1,881
    PG
    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.
     

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