"Cartridge Headspace Gage"

[Brad in Idaho]

I bought this a long time ago, and completely forgot about it. With the discussion on the M1 Forum here about the "Catastrophic Failure" of a posters M1 with his handloads, I have been doing more reading, and refreshing my own memory. I am prepping brass (all LC 69 in this batch) for loads for my M1's (multiple), and I remembered I had this gage, so out it came. I checked 100 cases I've sized, and of those, 15 do not gage as the manufacturer says they should. The case head protrudes beyond the second step of the gage (picture below), and according to the instructions, that means the shoulder is not set back enough. Thing is, the other 85 cases gage as they should. So if I were to readjust my sizing die to accommodate the 15, I would be pushing the shoulder back too far for the majority of the cases I size. At this point, I have set aside the 15 and am looking for advice from any of you who use this type gage.

Several questions come to mind. Firstly, how important is this? I have loaded and fired my own ammo in several different Garands with no problems in the recent past without using this gage. I understand that if the shoulder isn't right, the round may not chamber properly, but how far off does it have to be to matter? The picture below is a good representation of the amount of protrusion on the 15 cases. Who here uses these gages for Garands? Should I just discard the cases that don't gage properly, or just accumulate a bunch of them, and resize them with the sizing die adjusted to accommodate them. How can the majority of this brass gage fine, and these others not? The die I am using is an RCBS full length sizing die. If any further pictures would help, I can provide them.

[Hefights]

It is typical with milsurplus cases that some percentage will not gage, most of those that dont look like what is in your pic. I bet the ones that stick up like that shoot just fine. I know mine do. Typically I only worry if they stick up farther than the one shown in your pic, that is if they stick up above the rim.

In reality using only the standard case gage, we are probably oversizing the cases and bumping the shoulders down past where they really need to be for the chamber in question. In theory thus overworking the brass and reducing case life. For a Garand or military semi auto, I am not going to go through the trouble it takes to try and tailor the sizing die adjustment to the specific chamber. I am not worried that much about brass life in this type of reloading, I get enough reloads out of my semi auto brass.

If you want to be on the safe side, you can toss them out. Or just as you say, try to adjust the die for a group of the outliers if you can and bump them down farther. I use a Forster COAX press so there is a limit to how far down I can adjust the die to bump the shoulder back, but it works for the vast majority of cases.

[edpm3]

Sometimes the case is properly sized but still sticks out like in your picture, because there is a burr on the case rim. It doesn't take much and it may be hard to see. A magnifying glass and a fine file can take care of it. Not all case gage rejects are caused by burrs, but some can be.

[Brad in Idaho]

edpm3, Thank You. I checked the 15 cases that stuck out, and every one had a tiny nick on the rim. A few strokes with a fine file, and they all gage good. That hadn't crossed my mind. They were hard to see, but running my finger around the rim found them just fine. The best part is it tells me I have my sizing die set properly. I have a bunch more cases to prep, I'll make checking for the nicks part of the process. Even with the nicks, if I applied a little more pressure to the cases, they would seat in the gage as they're supposed to. A Garand bolt pushing a round into the chamber would exert a lot more force, so these nicks wouldn't be enough to cause any chambering problem even if they weren't noticed. Thanks again.

[Hefights]

Wow, I wish mine were that easy. The nicked ones mostly will push down into the die and dump out with a tap on a board. That tells you your brass is good to go.

[Brad in Idaho]

Exactly Hefights. Nearly all of the cases I found with nicks would go into the gage properly with just a little more pressure, then tap the gage on the table and they released. I'd just touch up the rough spot with the file and they gaged perfectly.

I have gaged all of the 407 cases I sized the last couple of days and found 2 that would not gage, no nicks, or any other problem I could discern, they just wouldn't go into the gage enough. Crushed the necks with pliers and into the recycle brass bucket.

[PhillipM]

I use the RCBS case mic designed to check setback and bullet seating depth. The bullet seating depth is a bit cheesy, close to useless, but where the RCBS shines above the Wilson is all in the numbers. RCBS will tell you down to the .001" where the headspace is in relation to SAMMI. A cursory inspection of unfired factory ammo on hand shows HXP about +.003", WCC 56 tracer -.002" LC67 .000", LC69 +.001", Korean PS 75 -.002", and Rem, Fed, Win all .000". Yes, the RCBS is slower to use than the Wilson, but if you have a quality press with no slop, once the die is adjusted you are done with the case checker.

If I adjust my shell holder against the sizing die, I get a -.005".

The best thing to do is get the RCBS tool and measure a new factory round then shoot it out of your M1. If you are OCD, remove the gas plug so you know the case didn't deform in extraction. Now measure the fired case and compare to what it was before you fired it and where it is relative to 0 on the gauge. Now you know how much the case stretched in firing. Shoot a couple more and check them then adjust your press to the shell holder hitting the die and measure that case.

A book could be written on what to do with that data, but suffice to say if my original case is .000" and my fired case is .003", I am not going to set the full length sizer to touch the shell holder if that gives me -.005", I'll adjust mine to .000" so I don't overwork the brass.

...almost forgot, if the inside of the neck has not been lubricated, the expander ball will stretch the case on the upstroke.

I lost a lot of hair when I first got my case mic learning the above. I hope you have a shorter learning curve!