30.06- Case Gage Woes
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dmazur
Member
Well, the unwelcome advice would be "both".
The RCBS Precision Mic actually measures case head to shoulder datum, using SAAMI dimensions for zero. The "prototype bullet" and separate dial is supposed to permit measuring distance to lands, but as the prototype bullet isn't the one you are actually using, this may or may not work. (Many, I have read, use the RCBS Precision Mic for the first purpose and toss the prototype bullet stuff.)
The LE Wilson gauge is often used as a "drop-in" gauge to check for case head to shoulder datum (often called cartridge headspace), by looking at the head relative to a step cut in the bottom of the gauge. It also works to measure "trim length" by inverting the gauge / case on a flat surface and observing the case mouth at the other end, where there is a second cut step. The instructions describe how to use calipers in conjunction with the gauge to measure fired cases and resized cases.
I believe both gauges are deliberately oversized in diameter at the body so that there is no interference with measuring fired cases.
If I had to get just one, I'd get the LE Wilson and use it with calipers. When used as a drop-in gauge, it is fast enough to check an entire batch of brass for cartridge headspace and trim length. For setting up the resizing die initially, it can be used with a caliper instead of just "eyeballing" the head relative to the steps.
But the RCBS Precision Mic is a nice tool, too. Just not as versatile, IMO.
(Can't help with the rhetorical question...
)
The RCBS Precision Mic actually measures case head to shoulder datum, using SAAMI dimensions for zero. The "prototype bullet" and separate dial is supposed to permit measuring distance to lands, but as the prototype bullet isn't the one you are actually using, this may or may not work. (Many, I have read, use the RCBS Precision Mic for the first purpose and toss the prototype bullet stuff.)
The LE Wilson gauge is often used as a "drop-in" gauge to check for case head to shoulder datum (often called cartridge headspace), by looking at the head relative to a step cut in the bottom of the gauge. It also works to measure "trim length" by inverting the gauge / case on a flat surface and observing the case mouth at the other end, where there is a second cut step. The instructions describe how to use calipers in conjunction with the gauge to measure fired cases and resized cases.
I believe both gauges are deliberately oversized in diameter at the body so that there is no interference with measuring fired cases.
If I had to get just one, I'd get the LE Wilson and use it with calipers. When used as a drop-in gauge, it is fast enough to check an entire batch of brass for cartridge headspace and trim length. For setting up the resizing die initially, it can be used with a caliper instead of just "eyeballing" the head relative to the steps.
But the RCBS Precision Mic is a nice tool, too. Just not as versatile, IMO.
(Can't help with the rhetorical question...
)
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jr_roosa
Member
Yeah you should have both. They do two different jobs.
The precision mic is good for setting up your dies and adjusting as brass gets work hardened and a little harder to size. I adjust my sizer a little every time I use it. I also use the Hornady headspace gauge and bullet comparator instead of the RCBS, but it's the same concept.
The drop in case gauge is fast and every round that is going into an autoloader gets checked in one of these before going in the box. You can also measure headspace off one of these but it's a pain compared to the other gauges.
J.
The precision mic is good for setting up your dies and adjusting as brass gets work hardened and a little harder to size. I adjust my sizer a little every time I use it. I also use the Hornady headspace gauge and bullet comparator instead of the RCBS, but it's the same concept.
The drop in case gauge is fast and every round that is going into an autoloader gets checked in one of these before going in the box. You can also measure headspace off one of these but it's a pain compared to the other gauges.
J.
Grumulkin
Member
I haven't had either for several decades and have no plans to get one. I presume this is about the Garand? If so, it is highly unlikely that you will see any appreciable accuracy benefit with all the planned measuring. If you were loading for a bench rest gun it might be different.
dmazur
Member
If you're reloading for a Garand, it is customary to resize to minimum on a Wilson gauge, or 0.003" less than fired length.
The Wilson gauge will work fine for this, and can be used without calipers once your resizing die is set up.
It isn't about accuracy. It's about reducing the possibility of slamfires.
The Wilson gauge will work fine for this, and can be used without calipers once your resizing die is set up.
It isn't about accuracy. It's about reducing the possibility of slamfires.
I've never used case gauges.
My rifles have perfectly good chambers to test fit ammo in, no need to spend money on something that I already have.
If I were reloading for RESALE, yeah. Case gauges. But for personal use? Throw it in the rifle and see if it fits. If it don't, make changes.
My rifles have perfectly good chambers to test fit ammo in, no need to spend money on something that I already have.
If I were reloading for RESALE, yeah. Case gauges. But for personal use? Throw it in the rifle and see if it fits. If it don't, make changes.
Even with bench rest guns they are rather pointless. You're not moving the shoulder or body of the casing on those, only the neck gets sized.
(And necks turned. And primer pockets get uniformed. And flash holes deburred. And cases weighed. And you don't eat Pizza for two weeks before a match because it might give you gas and make you miss by .0001 MOA).
jr_roosa
Member
It's a real pain in the butt on my Garand. To get a good test I have to field strip it, remove the op rod and spring, and disassemble to bolt. Every time I do that it takes a few rounds to settle back down, and it gets a little looser in the stock too.
I just sized 150 pieces of brass this morning, and after resetting my die to get 0.002" short of my chamber, I could easily check every round for proper sizing (one or two came out about 0.004" long and needed another run through) with the drop-in wilson case gauge. Long ones were verified with the Hornady gauge on calipers.
It probably doesn't help accuracy much, but with my die set "all the way down plus 1/4 turn" the rounds get sized to about 0.010 short of my chamber. Brass is too expensive to waste by oversizing. Rifles (and fingers and eyes) are too expensive to waste by risking an out-of-battery slamfire. It's a 5 second check for each round to make me feel better about my consistency.
-J.
Hmm. The only gauges I use, are drop-through case gauges to make sure they haven't grown too long and require trimming.
If the die is set up properly to begin with, what would a second run through of the same die do to it, that the first run through did not do?
Are you measuring to the shoulder? Or the total case length? Because necks will grow inconsistently. The only time you can trust measuring the full length (mouth to base) is immediately after they've been sized and trimmed.
And why in the world would you have to disassemble your Garand to check anything? Load a dummy round and run it through (or a few). I've never had to dissasemble any firearm to check whether the rounds will feed and chamber.
If your die is not sizing brass fully, to the point you can chamber them, you need a different die. Plain and simple. Shoving the shoulder back does nothing for this if the web (base) is expanded out of spec. You could shove it back a half inch and the round still won't chamber.
Also, be careful about impacting the shell holder with a die that's adjusted too low. That's real rough on your hardware. At the maximum leverage you get at the end of the stroke that press is putting a LOT of pressure on things.
If the die is set up properly to begin with, what would a second run through of the same die do to it, that the first run through did not do?
Are you measuring to the shoulder? Or the total case length? Because necks will grow inconsistently. The only time you can trust measuring the full length (mouth to base) is immediately after they've been sized and trimmed.
And why in the world would you have to disassemble your Garand to check anything? Load a dummy round and run it through (or a few). I've never had to dissasemble any firearm to check whether the rounds will feed and chamber.
If your die is not sizing brass fully, to the point you can chamber them, you need a different die. Plain and simple. Shoving the shoulder back does nothing for this if the web (base) is expanded out of spec. You could shove it back a half inch and the round still won't chamber.
Also, be careful about impacting the shell holder with a die that's adjusted too low. That's real rough on your hardware. At the maximum leverage you get at the end of the stroke that press is putting a LOT of pressure on things.
dmazur
Member
If you're resizing 0.010" less than chamber length, I'm afraid that is overworking the case. The idea is to resize enough to guarantee chambering without resistance, but not more. From what I've read, this can be 0.003" to 0.004" shorter than fired length.
The practice of stripping a Garand bolt to use a true chamber headspace gauge is due to the stiff extractor and ejector, considerable spring force from the op-rod spring, etc. All of these make getting a "feel" for bolt closure on the gauge almost impossible. Much easier if the springs are temporarily removed. But also not something you want to do frequently...
While it may not make sense, I have had mixed brass problems when reloading for a Garand. Multiple passes through the same die, same setting, got another couple of thousandths. Something sometimes called "spring back"? Some swear brass can't do this, but when it work-hardens, apparently it can. (I solved the problem by using new cases and then tracking the reloading history of each "lot" of cases. No more mixed range brass for me...)
The practice of stripping a Garand bolt to use a true chamber headspace gauge is due to the stiff extractor and ejector, considerable spring force from the op-rod spring, etc. All of these make getting a "feel" for bolt closure on the gauge almost impossible. Much easier if the springs are temporarily removed. But also not something you want to do frequently...
While it may not make sense, I have had mixed brass problems when reloading for a Garand. Multiple passes through the same die, same setting, got another couple of thousandths. Something sometimes called "spring back"? Some swear brass can't do this, but when it work-hardens, apparently it can. (I solved the problem by using new cases and then tracking the reloading history of each "lot" of cases. No more mixed range brass for me...)
jr_roosa
Member
Oh, I don't do that anymore. Once I got a gauge and saw how much I was sizing my brass I changed my practice to the 0.002" pushback I do now.
I mention it because I bet that the majority or new reloaders out there who don't measure and don't know how much they are beating up their brass.
J.
jr_roosa
Member
I see that too. Sorting by head stamp and year fixed that. Also I see that if one is a little long another pass through takes it down about another 0.002" and even properly sized brass with a second pass will get shorter.
sage5907
Member
I went through the same thought process. I bought a RCBS case micrometer and Wilson guages. My intent was to size the cases to the SAAMI "0" line on the micrometer. I was shooting the cases in more than one rifle and I thought that if I resized at .002 shorter than the shortest chamber (the "0" mark) I could shoot the rounds in all of the rifles with minimum working of the brass. This was not entirely true, possibly do to springback in the brass, because I noticed at times I was getting a tight bolt closing on some of the rifles. Full length risizing pushes the shoulder back somewhere between .003 or .004 shorter than the "0" mark. Unless your chamber is exceptionally long I would recommend full length resizing and forgetting about purchasing the guages. If you were shooting factory ammo in your rifle you would have a cartridge at least .005 shorter than your chamber with every shot.
jr_roosa
Member
Yeah, factory starts out way short, but it is only stretches that much once, and then you are in control of the stretch after that. As long as you check for incipient head separation, and keep a broken case removal tool in your range bag, then you should be just fine with maximum resizing. The only downside is your brass will wear out sooner.
I'm a data guy, and I like knowing the numbers, even if they don't necessarily matter that much.
-J.
jr_roosa
Member
http://www.saami.org/pubresources/cc_drawings/Rifle/30-06 Springfield.pdf
Also, things can get weird with .30-06 since the allowable SAAMI case lengths overlap with the allowable chamber lengths (I'm talking about headspace here at the 0.375" datum on the shoulder, not OAL or length from the base to the case mouth). This means that an in-spec SAAMI .30-06 case that is at the long end of the range (2.0456" to 2.0526") is actually longer than an in-spec SAAMI .30-06 chamber that is at the shorter end of the range (2.0487" to 2.0587").
GI spec cases can run even longer (2.0482" to 2.0542" according to Hatcher's Notebook). I just found out that my HXP80 rounds fresh out of the spam can are so long that my Garand bolt won't close on them unless it is loading them out of the magazine with the force of the op rod spring to crush the shoulder back a little to make it fit. This sort of blew my mind until somebody pointed me to the chamber prints and case dimension drawings.
You just don't know until you measure.
-J.
Also, things can get weird with .30-06 since the allowable SAAMI case lengths overlap with the allowable chamber lengths (I'm talking about headspace here at the 0.375" datum on the shoulder, not OAL or length from the base to the case mouth). This means that an in-spec SAAMI .30-06 case that is at the long end of the range (2.0456" to 2.0526") is actually longer than an in-spec SAAMI .30-06 chamber that is at the shorter end of the range (2.0487" to 2.0587").
GI spec cases can run even longer (2.0482" to 2.0542" according to Hatcher's Notebook). I just found out that my HXP80 rounds fresh out of the spam can are so long that my Garand bolt won't close on them unless it is loading them out of the magazine with the force of the op rod spring to crush the shoulder back a little to make it fit. This sort of blew my mind until somebody pointed me to the chamber prints and case dimension drawings.
You just don't know until you measure.
-J.
sage5907
Member
jr roosa, I used to think that when a case was fired it would expand to the full size of the chamber but that is not always true. I have checked the case chamber length of many fired cases and what I have found is that when a new case is fired and then neck sized it may take as many as two firings to fully expand to the full length of the chamber. I am talking about a 30-06 with 150 grain bullets loaded to normal pressure. If a new case is .003 shorter than "0" saami length it may only stretch to the "0" length and if you reload it again with full length resizing you may only be setting the shoulder back .003. Doing this does not excessively work the brass and the reloaded cartridges chamber easier because even when fired they are about .002 shorter than the rifle chamber.
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ArchAngelCD
Member.
I bought a Lyman last month for only $18.95 at my local gun shop.
The Lyman looks every bit as good as the LE Wilson and is just as good. (they are probably made by the same manufacturer)
http://www.midwayusa.com/product/270484/lyman-case-length-headspace-gage-30-06-springfield
It's my new baby and by the looks of the barrel, has never been fired more than a handful of times. It's also a national match rebarreled in 53. I'll never win the real lottery, but I won the gun lottery on this one. Chalk it up to damaged op rod and gas plug horror stories, I'm way paranoid. And this past weekend I got a round stuck in the chamber. For various reasons, most of which involve opporator error.
jr_roosa
Member
I'm jealous, Ali! Good luck figuring out reloading for it. You will think you l ow what's going on and then something new will surprise you. You can download a PDF copy of Hatchers Notebook and read the chapter on headspace. It is very enlightening.
Good point, sage.
In my garand it gets even weirder because the cases come out of the chamber with various lengths, maybe from extraction stretching, maybe from the shoulder getting pushed back even more from chamberig. It seems that the biggest change is in how fat the body is, making it impossible to get a fired case back in the chamber.
I have to use cases sized back various amounts as poor man's headspace gauges to empirically figure out the size of my chamber. I have dreams about getting a bolt action some day where the reloading is easier!
J.
Good point, sage.
In my garand it gets even weirder because the cases come out of the chamber with various lengths, maybe from extraction stretching, maybe from the shoulder getting pushed back even more from chamberig. It seems that the biggest change is in how fat the body is, making it impossible to get a fired case back in the chamber.
I have to use cases sized back various amounts as poor man's headspace gauges to empirically figure out the size of my chamber. I have dreams about getting a bolt action some day where the reloading is easier!
J.
hueyville
Member
In 35 years at this game I have never used case gauges. I do use a bullet comparator to set up my bullet seating depth from lands on some rifles but never seen a need for a case gauge. I either full length size or neck size. If for a repeater I use small base dies for full length sizing. No issues with this method hundreds of thousands of semi auto rounds later. I don't use the comperator for semi autos either. I set them up to SAAMI maximum OAL using proper bullets and let fly.
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