Perhaps this belongs in the Reloading forum, and I will move if appropriate or I don’t get many responses here:

I’m learning new stuff here on the the ‘Fire about reloading. Considering my age, I kinda hate to admit that. On the other hand, learning new things is great. I’m learning from many, but especially mathman and Dirtfarmer. And of course Mule Deer.

I’m learning that with the highly regarded Lee collet neck sizer dies, occasionally you need to move the shoulder back. I’ve learned what a body die is and that you can make a pretty good one from the Lee full length resizing die. (I’ve also learned what a bump die is and how it is not quite the same as a body die. Different topic.) But whichever I use, I probably don’t want to move the shoulder back as much a body die is capable of. Instead, I want to move the shoulder only a few thousandths. So, I need a good measure of the head to shoulder dimension.

What method or commercial devices do you use to measure the head to shoulder dimension on cases?

I load a lot of rounds based on the 308 Winchester case. For those I use a real fancy tool, a deprimed 40 S&W case.

I put the 40 case over the case neck of the rifle brass and measure the whole thing with calipers, before and after sizing. The difference of the lengths is the amount of shoulder bump.

^^^^^^^
I've read that before, likely from you. I bet you always use the same case too, unless you are willing to reestablish your reference every time. In addition, I suppose that method works a lot of places so long as the "measuring case" rests on the shoulder of the case to be measured. After all, the datum diameter is probably just the diameter the designer picked. Nothing really special about it.

I use my Hornady LNL comparator tool. The actual measurement doesn't mean much, as long as it fits over the neck and touches the shoulder. I use the one that's meant for measuring Ogives, but I have the whole set so I end up using whichever collet goes over the neck of my intended cartridge to take the measurement.

https://www.hornady.com/reloading/p...uges/headspace-comparator-anvil-base-kit

Hornady bullet comparators will serve the purpose. For instance, you can use the .35 cal bullet comparator to get a reference measurement on the shoulder of a .30 cal case, or a .30 cal comparator insert on a .223 case.

Can't beat a Stoney Point (Hornady)

I like the Redding Instant Indicator.

It's expensive, specialized - but it can do datum line, case length and OAL measurements too - a tool that makes it easy to get a reading that's good enough - all the more because I'm using a relative measure. It's quick and easy for repeated measurements, easily zeroed with a set of go, no go and field gages and I have head space gages by thousandths for .223/5.56, .308/7.62x51 and .30-'06/7.62x63. Paying for convenience but time is money too. Makes it quick and easy, encourages checking for spring back and doing things right. Well set up the Redding is robust and maybe calipers and micrometers are more fragile. No need to have bodies and dial indicators for every cartridge and of course one tool will cover a range on both sides when the head to datum is similar like the .308 family with a range of bushings that are likely to be on hand anyway. Then too though it's well worth having anyway, one additional justification I used for adding a T7 to the collection is having the Instant Indicators and the dies all set up simultaneously. Like having a caliper set-up with the Hornady adapters for each cartridge without tying up a good caliper.

I also have some Hornady (and some from previous ownership) despite using a Starrett digital (serial port and machinist's milk tolerant but not worth the extra money for reloading bench use) I don't trust the readings to all the indicated places for actual dimensions. I also have Wilson case gages (and cartridge gages not the same thing and trimmer shell holders also not the same thing) and RCBS plastic micrometer style and Case Master dial tools.

In effect I started with L.E. Wilson gages and relative eyeball measurements and never had a complaint but I wanted a little more convenience and better numbers as time passed and the number of cartridges loaded - and the same cartridge in a break action, a gas gun and a bolt gun is sometimes not really the same cartridge - so I went what I think is deluxe.

For a tool, just about anything with an appropriately sized round hole that fits in your calipers will work. The hole size should be such that it makes contact about halfway up the shoulder. I make my own from pieces of barrel cut-offs.

Always zero on a fired case from the same rifle:


Then measure shoulder bump after sizing:

I use both the Hornady/Sinclair "comparators" and the Larry Willis "Digital Headspace gauge"...

There is no need or reason to measure, simply adjust the sizer so cases chamber with a tiny amount of resistance,.

You can sure get by using that method. Truth be told, if I move a shoulder 0.002" and still don't like the way it feels closing the bolt, I'll go another 0.001" or so...but I like being able to measure for the ease of making that adjustment. It doesn't take much movement of the lock ring the change it by too much. But you're right, it ultimately has to feel right when closing the bolt.

Exactly...if one NEEDS a measurement, stick tape on the case head, close the bolt. Measure the thickness of the tape when it feels good. About three thous, or two applications of tape.

You can do that if you want... But actual measurement before and after like I showed in the pictures above is easier, faster, and more accurate, even if you're just using an empty 9mm or 40 S&W case instead of the tool attached to the calipers. I can't see any reason to bother with tape.

Here's an article I wrote on die setup and shoulder bump last year that might help. The Sinclair Hex Bullet Comparator I used is designed for measuring OAL to the ogive, but by using a larger caliber hole than the cartridge you're loading for lets it seat down on the shoulder of the case to measure shoulder bump. Since the nut I have only has holes up to .30cal it only works on cartridges up to 6.5mm, but it's easy enough to make your own by purchasing a 1" nut (on the flats) and drilling the appropriately sized hole(s) into one of the flats to meet your needs. Sinclair also offers a second version for .17, .20, .224, .277, .308 and .338 calibers that will allow you to do up to .30 cal cartridges.

http://www.savageshooters.com/content.php?476-Sizing-Die-Setup-and-Shoulder-Bump

Yea boy! This works in spades!

https://www.midwayusa.com/product/3...-comparator-complete-set-with-14-inserts

for use on cases with no bullet

This is true, careful die manipulation, 1/16 turn at a time. When you get done, smoke a case with a candle or cigarette lighter, and carefully chamber the sized case after wiping the lube off the case.

You should see slight deformation of the black soot on half of the shoulder. If you do not see this, you have probably pushed the shoulder back too far.

Measuring is just easy, write the length down in the top of the die box or in a note book for that rifle with that particular barrel. Check more than one case as brass spring back is a real bitch to deal with as brass gets work hardened along with the fact that there maybe as much as 6% variation in hardness within a single lot# of brass.

Done that too...uses a .45 LC or 357.
It works.

I set my die up by using a fired case, sizing down till the bolt closes with no resistance. I will also check bolt close on a different make of brass, adjust if needed. YMMV.

Same here, but I opt for slight resistance when closing the bolt, or ,when I had my M14, reliable closing of the action with a full magazine. None of this small base die FLS nonsense - I wanted my cases to last! (and they did)

If you do the arithmetic, turning the die in 6 degrees---a single tick of the second hand of a clock, the shoulder should be moved further back by a little over 0.001 inch. Getting it exactly where you want it is a precise and tedious operation. That's why I leave the locking ring set once I've adjusted it.

^^^^^^^
Good post! Puts things in perspective.

Been loading over 50 years and this is what I do. Numbers don't mean a thing if the cases don't fit YOUR chamber.

Why bother with weighing powder? Just put in what looks right.

I've had the stoney point headspace gauges 20 years, from back before Hornady bought them out. They've long since been amortized and it takes about a second to mount it on my calipers. Going by the "slight resistance when closing" method can fool you because there are other things than the shoulder that can cause the same feeling like an expanded case head or tight neck. Measuring something instead of guessing is never the wrong answer.

+1...... To what Crow hunter said.... Got my Stoney Point headspace gauges back around the mid 1990's IIRC. I have all the headspace data written down for each rifle. Put gauge on caliper; take measurement and instantly know what the story is. I think the folks at Hornady recognized what a great product Stoney Point had and that's why they bought 'em out. Nice part is that they didn't change anything. I can buy a Hornady bushing today and use it on my 20-something year old Stoney Point tool.

That's a pretty solid indication you don't understand what we're measuring or why. The zero measurement I showed above is on fired brass from YOUR chamber. The entire point of measuring is to know where the shoulder is set relative to YOUR chamber. It ain't hard, but without measuring you're just guessing.

All of the techniques described above to avoid measuring headspace are more tedious and less accurate than just measuring it.

The Forster Datum Dial Measurement System works very well for measuring case headspace in my experience. It clamps on a vernier caliper and measures the headspace for unfired and fired brass in the specific bullet cases offered in the set. Standard set measures from 17 Rem to 375 H&H.

https://www.forsterproducts.com/product-category/inspection-measurement/datum-dial/

It's very easy to measure fired brass for each of your rifle chambers. Then size your brass in to the spec measured by the datum dial.

Bruce

Great thread - great info. ..

So you are measuring the distance from the base to a datum on the shoulder(headspace). As I understand you, you are then setting the shoulder back some amount (.001-.002) Why? If I PFL size or necksize. I am not touching the shoulder so am working my brass less. When PFL or necksizing no longer allows chambering, I FL size just enough to once again allow chambering. What does knowing the dimension to an arbitrary datum gain me? What have I been missing all these years?

I do the same thing Blacktailer, and have been for years. The only reason I bump shoulders back is when brass gets a little too tough to chamber. My brass lasts a very long time.

I think at least part of the percieved issue here is about different applications; what works for a guy shooting 10-20 shots from a bolt action may not work for the guy shooting 500 rounds through a semi-auto, for example.

Partial full length sizing is certainly a viable option in some bolt action and single shot applications, and I've done it quite a bit myself. It does not work for everything though, and makes closing or opening the action unreliable in some guns (most semi-autos and pump actions for example, or when firing a lot of rounds in a bolt gun and the chamber gets fouled or dusty). This discussion is not about partial full length sizing though, or about neck sizing.

Measuring shoulder bump comes into play when you FL size. Instead of guessing "just enough", you can actually measure exactly enough shoulder bump to be correct for your chamber. It's less critical in a bolt action in a clean environment with plenty of camming power, as long as your "just enough" isn't too much, but in other actions or in severe environments, the ability to measure and bump the shoulder the right amount can be the difference between a gun that won't cycle or extrac, and having excessive headspace.

One example I'll point to is the commonly suggested method of adjusting a sizing die down in 1/8 turn increments until the action closes. If you actually measure (or do the math on die thread pitch), 1/8 turn is equivalent to ~.009", meaning one increment can take you from not closing the action down to excess headspace. If you're actually measuring shoulder bump, you'll catch that immediately, but without measuring it would feel fine and the owner wouldn't realize the headspace problem he created.

Agreed. Pumps and autos are a whole different animal.

Good explanation of the process here:
https://youtu.be/Qd583ZMYncE

+1

I wonder...if partial full length sizing doesn’t bump the shoulder back, wouldn’t it potentially move the shoulder forward since the side walls are being partially compressed, forcing the shoulder forward??

It does...but try it your self to see.

Run the die down to your lock ring. Just so you know where you`re at. Then turn back out 3-4 full revolutions. Start sizing the case, and move the die down 1/2 turn. Check the case in your rifles chamber after each turn. Do it again etc. See what happens.

Yes, that's exactly right. As the body diameter (at the shoulder) is squeezed inward by the die, the shoulder moves forward gradually, up to the point that the die shoulder contacts it and pushes the case shoulder back.

Results vary of course, but in a number of different cartridges I've measured .001"-.002" shoulder set forward. The maximum set forward happens right before the shoulder is set back. If you're partial full length sizing and leaving a significant part of the neck unsized (like 1/4 of the neck, maybe), the shoulder set forward happens but is very small; I've measured .000"-.001" max. In a bolt action with plenty of camming power, that is no problem at all. In something like an AR15 - it can work, the bolt will close, but it is usually very hard to open again unless you fire the round.