Are there any tricks to measuring shoulder bump besides purchasing a gauge such as the hornady or sinclair?

An in-expensive option I have used has been utilizing a empty pistol case and caliper to reference length of fired case vs a case that has been lightly bumped. Removing the primer on a fired pistol case helps with consistency.

Otherwise slowly working up to bumping the shoulder back in very small increments and testing the fit when closing the bolt. Perhaps placing a layer or layers of tape on the base of your cartridge, to test fit after bumping the shoulder back to gauge the fit may work for you if you are working with a bolt action.

Decap a 9mm case or a .38 special or 357, mark it with a Sharpie so you know which one you used.
Invert the pistol case and place it over the neck of your cartridge case and measure, make sure it's long enough to touch the shoulder only.

It will give you a reference number, make note of a fire formed case length and a sized case and it's easy to be sure you're not bumping the shoulder too much.

Set the die for that rifle and you're done.

Hunterapp beat me by 2 minutes!!

A piece of pistol brass is certainly the quickest way to get started on this. Any piece of tubing of the right size will work though.

I like to make my headspace measurement bushings from cut-off barrel sections, and mark them for the case they are intended to measure. No particular reason for using barrel sections, except I already make a similar bullet ogive measuring tool using them.

If you're not familiar how to measure shoulder bump-

Zero caliper on a fired case (check with several):


Measure shoulder bump on sized cases:

I discovered different hardness of brass will give different amount of set back. It's a very good idea to have all the brass annealed the same.

For this reason and others I'm not as concerned as some others with how good die lock rings are. I adjust dies pretty much every time I use them.

Individual cases, even when fired the same number of times, will also vary slightly in dimensions after FL sizing. Which is why I generally just adjust the dies to a slight "crush fit" average for bolt actions.
Or at least I do that for big game rifles. Cases for varmint rifles are often neck-sized if fired in the same rifle.

This ^^^^^^

I've NEVER measured the 'set back'. This is no hassle.

Jerry

I'm having trouble understanding how there can be a crush fit after sizing when the fired case shouldn't be larger than the chamber to begin with.

I'm not being sarcastic here. I really want to learn. I can chamber a fired case in my rifle without much more effort than a factory round so I'm not understanding how you can adjust sizing dies going just by feel of chambering a round.

When the body of a case is sized it gets squeezed down radially, but the case can grow lengthwise. That is, the shoulder can wind up farther away from the case head than before sizing unless the die is adjusted to control this dimension.

Thank you mathman.
I didn't see that happen when I was setting up my FL sizing die. I have an RCBS FL sizing die. I was using a sinclair bump gauge to measure as I gradually adjusted my die down. The case head to shoulder distance never grew. It stayed the same as a fired case until the die adjustments started bumping the shoulder back. I stopped at .002-.003 bump.

The effect can vary with the taper of the cartridge design, and how much taper the size die tries to put on the case. For example, my Hornady 308 Win. FL size die squeezes and tapers the brass noticeably more than my RCBS die.

In 308 I have FL dies from Lee(2), Hornady, RCBS, Redding, Forster, and there may be a Lyman buried in my gear stash. They all move the brass differently.

I wasn't aware there would be that much diff between brands of sizing dies.

I've never had diff brands for the same cartridge at the same time.

Good to Know - Thnx

Jerry

I've used my bullet comparators to check shoulder bump a few times and I don't see why it can't be just as useful a technique as comparators made specifically for shoulder measurement. As an example (IIRC), the .30-cal comparator can be used for shoulder measurement on a .223 case. I generally use collet neck dies anymore, but if I have to set up a FL die I go by feel, making use of the fact that the shoulder will often flow forward slightly before it contacts the surface in the die which pushes it back. Very small adjustments of the FL die will move the shoulder 0.001 inch.

Empty straight wall case works
Socket from your toolbox works

Anything that hits close to the C/L of the shoulder datum

Or a custom sized tool made to hit the C/L of the shoulder datum like all of mine are

I know this is an old thread but I appreciate the info. The socket method is what I went with and it works great for my needs.

If you check, you'll never chamber a factory round that will not chamber easily, their all made the SAMMI spect's and chamber's are cut to the same speck's. When you fire one of those, the case will move forward slightly and then back to the bolt face. The case will cool enough to allow the fired case to be ejected. Most people load to those spec's weather they know it or not, that's what full length die's do! Other's neck size, even with FL dies by not squeezing the case down past the bottom of the neck. problem is that every few round's, the case will have expanded enough to not re-chamber again after it's loaded. People that do that simply FL size again and start over. Other's partial size, actually wrong thing to call it IF your sizing only enough to chamber a round even though you can feel the shoulder rubbing in the chamber with the bolt closing.

I do not care for the crush fit I partial re-size. I shoot a case a few time only sizing about two thirds wat down the neck, you can see the sizing die leaves marks where the case stopped with the ram all the way up. i do that until I can no longer get a fired case back into that chamber. From there I run the die all the way down to the shell holder and then back out about a half turn. Try the case and it will not chamber without rubbing at all, maybe won't chamber at all. The shoulder need's set back! Turn the die down 1/8th inch each time the case won't chamber without rubbing, it'll take a number of tries. What your doing is slowly setting the die to re-size for that chamber. I keep going down just a bit until I can feel no rub chambering the case.First one with no rub is where I stop. I do not want to be out hunting and find out that one round simply will not rub. Of course you can try them all before you go but you find one and you need to pull the bullet and dump the powder simply because you cannot re-size a loaded case!

Run the ram up to the die with a case in it and lock down the die right there. Leave it locked even when you take it out and that die will be set as long as the lock ring isn't move for that rifle. Each of my rifle's has it's own die set.

When you reach that point you will have bumped the shoulder just a bit. You'll also bump the entire case just a bit. You cannot bump the shoulder with out bumping the whole case!

Then, I am a guy that use's only one bullet shape and weight in a rifle. So to seat a bullet, I start with the bullet set to the junction of the neck and shoulder.

To se the seating die to seat the bullet just short of the lands, I use a dummy load. Seat a bullet maybe half way down the neck. Run it easily into your chamber. You probably won't be able to close the bolt. Take it out and look at the ogive of the bullet, you'll see mark's on it where the bullet touched the lands, that's the ogive of the bullet. clean the marks off with a small piece of 0000 steel woll and turn the die down maybe 1/4 inch and try again. Do that until there are no longer marks being left on the bullet by the rifling. Then run that round back in with out moving the seating spindle and lock it down there. That seating depth will work to keep the bullet off the lands no matter which bullet you fire. Reason is that the distance from the bolt face to the land's will never change regardless of the bullet used. anf the dia of every bullet that dia will be the same at that point no matter which bullet is used.Keep in mind that when bullet's are made, the placement of the ogive changes just a bit but the dia at the ogive never change's.

Do yourself a favor and get a set of Redding Competition shell-holders and forget most of what you think you know about measuring shoulder bump. Cranking in a die an eighth of a turn at a time might seem precise but it is 1 divided by 14 divided eight, or with the tiniest bit of rounding .009" at a time. Factor in that the die is up flapping in the breeze and at the mercy press flex and brass hardness so you are measuring with micrometer and cutting with chainsaw. Heck, you're cutting a moving target with a chainsaw.

I did the calculations one day. Screwing the die in as far as the second hand moves in a single tic (that would be six degrees) will set the shoulder further back by little tiny bit more than 0.001". That's not much turn at all when you're thinking you'd like to keep from pushing the shoulder any more than two or three thousandths.

Setting the die like that take's a bit of time but once set is locked and never moved again. Die is dedicated to that rifle.

Problem I see a lot is reloader's wanting their hunting rifle to shoot like a match rifle. It's fish and foul! Your hunting riffle will seldom ever shoot like a match rifle. Not to say that now and then the hunting rifle won't blow your mind, some will!

You use all the tweek's and get your rifle down to constant 1/2" group's, and you'll never win against a match rifle with it and it won't take anymore game than a 1 1/4" rifle. Most people don't have the tool's to measure to one one thousand inch in a group either.

My goal with hunting rifle's is 1". varmint rifle's are never accurate enough, they are for fiddling with!

I view minimal shoulder bumping as a way to maximize case life and little else. With the Competition seaters its so easy that there is little reason not to unless you need the ammo to fit in more than one gun. Then size for the short chamber.


A side benefit is that the same dies can be used for multiple rifles without adjusting the sizer again so there is no big reason to have dies for each rifle.Just keep track of which shell-holder is for which gun. I write the number on the die box and shell box. It also eliminates the need for shoulder measuring tools. Heck, not having them is losing you money.

This is the best way to do it.

https://www.youtube.com/watch?v=WfWS7R1CdZI