Case gauge or comparator set?

[Ponder_MD]

When resizing your brass, do you prefer to check them with single caliber case gauges or a comparator set?

- With a comparator set and caliper, I can use a case fired from my rifle as an example and set the shoulder back 2 thousandths when resizing so that they will safely work in MY rifle and not overwork the brass.
- With a case gauge, this basically sets the shoulder back to a SAAMI standard that will work safely in any rifle but it may work the brass harder.

Is that correct?

 

[Park ranger]

rcbs precision mic for the win.

 

[Ponder_MD]

rcbs precision mic for the win.

Ok, I'm looking.

Precision Mic | RCBS

RCBS Precision Mics determine chamber headspace and bullet seat depth by measuring from the datum point on the case shoulder to the base of the case.

www.rcbs.com

If I take your meaning, my understanding is correct and you're showing me a more convenient tool to find the datum point?
It looks like you adjust the threaded section of the dummy round and then measure it with the adjustable case gauge?

 

[Park ranger]

Ok, I'm looking.

Precision Mic | RCBS

RCBS Precision Mics determine chamber headspace and bullet seat depth by measuring from the datum point on the case shoulder to the base of the case.

www.rcbs.com

If I take your meaning, my understanding is correct and you're showing me a more convenient tool to find the datum point?
It looks like you adjust the threaded section of the dummy round and then measure it with the adjustable case gauge?

right. You take a measurement of the fired piece of brass. Say it reads 5. Then adjust your die to where it gives you the bump you like, I typically do 2-3 under in bolt guns. Zero is basically a go gauge setting, and that’s what I size to for auto’s. Biggest lesson I learned from them is how much you can easily oversize a case.

 

[brianns]

The dummy projectile is used for another function. The precision mic does two things. I’ve only used it to measure a specific headspace for a specific rifle chamber. I think the dummy projectile/cartridge is for seating depth, which may change for different projectiles.

 

[Ponder_MD]

The dummy projectile is used for another function. The precision mic does two things. I’ve only used it to measure a specific headspace for a specific rifle chamber. I think the dummy projectile/cartridge is for seating depth, which may change for different projectiles.

Oh, I see. You use the mic on your spent case. The dummy cartridge is for seating depth. I had it wrong.

I can see how the precision mic is simple and easy but it's caliber specific. A comparator set with a few dies covers a wide range of calibers but not as convenient to use. There's a lot of debate on the internet about just full sizing or chasing the shoulder bump in autoloading rifles.

Frustrating for a new guy. I'm just trying to make safe, reliable ammo. I'm not shooting for the F class.

 

[brianns]

For auto loading rifles use a full length resizer. But if you try to get close to the chamber and set back to it you ought to keep those cases for that specific rifle chamber. The idea is to only bump the brass as little as possible for longevity. So you might be over Saami or too long for other rifles and have issues if you get into fine tuning the headspace with one of these micrometers. It’s caliber specific because the zero line is the saami spec. Either high or low end of the saami specification for headspace.

I don’t have the instructions in front of me. I just started using the RCBS mic recently for my M1A. I’m new at that level of measuring. I’m more used to using a non adjustable case guage for everything else.

 

[atblis]

The Hornady set that clamps on a caliper is most useful IMO. $40, covers a bunch of different calibers.

The Redding competition shell holder set is nice because once you measure you now know the shell holder to use to achieve the same bump.

The case gauges that indicate max and min SAAMI are useful for setting up batch processing of mixed brass that’s intended for use in multiple guns. Goal is to get all cases inside SAAMI spec, and cases will resize differently depending on multiple factors.

 

[Growler215]

When resizing your brass, do you prefer to check them with single caliber case gauges or a comparator set?

- With a comparator set and caliper, I can use a case fired from my rifle as an example and set the shoulder back 2 thousandths when resizing so that they will safely work in MY rifle and not overwork the brass.
- With a case gauge, this basically sets the shoulder back to a SAAMI standard that will work safely in any rifle but it may work the brass harder.

Is that correct?

Most case gauges that I've seen have two datum. Level with the lower datum is SAAMI min, level with the upper shelf is SAAMI max headspace. It also contains a recreation of a chamber to tell you if you have any other problems that could prevent chambering, e.g. brass too long, base too fat, etc.

I have both case gauges and comparator inserts for most calibers I reload, but use the comparator more.

 

[Ponder_MD]

The case gauges that indicate max and min SAAMI are useful for setting up batch processing of mixed brass

This is exactly what I'm doing. I'm not trying to get 10 reloads out of a single set of brass. Maybe I'm overthinking all of this and should just use the min/max SAAMI gauges.

 

[atblis]

I live right up the road from you if you'd like to borrow and try both types.

 

[Chauchat]

... I'm not shooting for the F class.

No, but you should reload as if you are shooting F Class or PRS or ultra long range . You will not blow up a rifle if you stick with published loads AND don't use pistol and shotgun powders or have barrel obstructions in your arms (Rright to bear arms). Any skill set that can get you food in a S H T F or 1775 to 1781 situation is a good skill set.

The chambers across my M1903, M1917, and Garand are all cut about the same. Why are they about the same? Who knows but being able to gather data gives me serenity when I pull the trigger. My RCBS die is set and will feed them all. Or to quote a movie... "One die to rule them all."

Plus! Suppose you can get 10 reloads from your brass. Money not spent for brass is money for powder and bullets.

 

[Ponder_MD]

@Chauchat thanks, I appreciate your input! Yes, I am absolutely sticking with published loads.

 

[Ponder_MD]

I live right up the road from you if you'd like to borrow and try both types.

I have a SAAMI gauge. Once I fire some rounds, I might like to borrow your comparator set. I have 2 Garands so I'd like to set my die to rule both of them.

 

[Growler215]

I've currently got 7 rifles chambered in 7.62x39. Looking to add a few more.

Keeping track of the headspace for all of those requires writing measurements down.

I also have a bullet comparator, used with modified cases to measure the maximum Cartridge Base To Ogive (CBTO) for individual rifles and bullets. I can then load to whatever "jump" distance I want. I also record the CBTO for every load I do, because for some/many bullets, this distance is much more consistent than OAL measurements.

 

[Speed3]

Comparator and measure base to shoulder, as park ranger mentioned bump it 2-3 thousands. Check after a few firings though, what WAS 2- thousands can change. If you don't catch it, you WILL overwork brass and end up with the dreaded doughnut ring or worse, case head separation.

Sucks to have those on brass in general, but also sucks when its lapua brass that you've spent the time turning necks on(speaking from experience lol).