I am a bit confused on headspace. Let's use my 204 Ruger as an example. Using my Stoney Point Headspace Gage, headspace on my once-fired brass measures 1.555. Now do I use this as my headspace measurement when loading them for the second time or is it necessary to bump back the shoulder a few thousandths?? I checked and the once fired cases do chamber freely in my rifle.
I also checked the OAL of the cases and they did stretch a few thousands so I know that I need to trim them back but am still confused on the headspace issue.
Will the same answer apply to my 7mm Remington Magnum?

1. Check 15 or 20 cases with the Stoney point tool. You will find they vary .002 or so.

2. I like to find a case from another rifle that has a longer chamber than my rifle. If not I like to neck up a case and then neck it back down until it will chamber with some friction. That maybe be .002 longer than your fired brass.

3. Set your die to push the shoulder back enough that you can barely feel a tiny bit of drag with your bolt stripped.

4. Since your .204 is a varmit rifle you could leave your dies set there unless you expect to get charged and need rapid fire to knock off a wood chuck.

5. For your 7mm Mag I would check it the same way but push the shoulder back at least .001 to .002 to insure feeding if you hunt big game with it.

Just keep in mind the following:

With this small push back you need to check every case that you size until you understand how they vary.
1. Variations in the amount of lube can vary how far the case slides up into the die.
2. The speed that you size the case can vary the headspace.
3. Dwell time at the top of the stroke can vary the headspace.
4. The rigidity of your press can etc.
5. I suspect that variations in the hardness of the brass from one case to another, one lot to another and one brand of brass to another can all affect the variations in headspace.

Fortunately you can detect the variations by measuring each case. .001 is not much variation but you can measure it and if your die is set too long or the brass for some reason is not sized enough (lube or speed) your bolt will drag on closing.

I get around this by cycling the press ram off of the top of the stroke, partially rotating the case and cycling again. It is sort of difficult to do that with a short round like a .204 so you might have to toggle the ram twice with out rotation. Do not pull the case over the expander but once. That is just unnecessary working of the brass.

If multiple press strokes are too tedious just set the FL die to push the shoulder back and check every case to make sure it will chamber.
With a little time invested you will learn exactly what will work.

SR4759 has said it all very nicely. One thing I have noted when using this method is that if you start off with one case that is too tight in the chamber and screwing the FL die down a fraction at a time until you get the bolt closing with just a hint of a drag on that same case, the next cases you size with the die locked at the correct setting will usually chamber without that slight drag i.e. a single stroke of the press to size a case will set the shoulder back just a fraction too much.
I now use 4 or 5 cases and only stroke them once as I set the die down, in other words when I finally get the die set to have the bolt feel a slight drag, that last case in the batch will have been sized once, not in multiple stages, to get the shoulder just right.

The earlier cases used to set the die can then be sized and will be very close to snug fit while all the rest of the unsized cases will be spot on when run through the die using the normal amount of lube and a single stroke of the press. To ensure consistency just like using a powder measure, the press should be stroked the same each time when setting the die and when sizing cases.

The posters have given good replies.

I find that cases are properly fireformed with nice crisp shoulders after two loads. I measure the headspace on my Stoney Point (now a Hornady Lock n Load I think if you buy a new one) for once fired cases and the twice fired cases.

I then set up the dies to bump the shoulder back around 1.5 to 2 thou. This is close to the once fired diemsnions. I'll set up with one case adjusting as I go until I get a number that I want. Then I will confirm my setting with a fired case that I size just once and tweak from there.

I'll add that not all brass will give you the same results either. Remember that as you size the case headspace will first decrease (or put differently the number you read on the calipers will get bigger) before increasing. This is because the case head to shoulder datum length increases as you size the base of the case down, until you hit the shoulder and shorten it again. You learn a lot about what sizing does to a case with these gauges.

A set of Skips shims or the Redding Competition Shellholders can be useful if you load several rifles in the same caliber. Finally, the Redding Competition Shellholders worked for me with Redding dies, but with some other highly regarded brands the dies could not be screwed down to touch even the highest shellholder in the set without sizing too far. Now whether those rifles are in spec is another question I suppose.

Wow Fellas, I didn't expect such detailed responses...Thank You!

I read your responses over several times but let me ask you this:

So regarding my once-fired .204 headspace reading of 1.555, SHOULD I pump the shoulder
back 1-2 thousands or can I just load it again as is since my bolt closes on it??

In other words since my once-fired brass is fire formed to my chamber is the 1.555 measurement the headspace I should use?

For the 7mm since it is a big game rifle, should I just bump my once-fired shoulder back 2 thousands and leave it at that?

Fellas you gave great responses but since I am new at this I am a bit overwhelmed...sorry!

THANK YOU ALL!

Frank

Here is the non technical answer: Why are you measuring headspace of a cartridge? it has no meaning unless paired with the actual dimensions of your chamber. If you fired the brass in your rifle and it fits back in after you neck size it; it is good. If you have a target rifle that give a slight "feel" on the bolt closing, that is good. For a DG or big game rifle, give it a bit more clearance to insure no hangups in the field. Too much data is not necessarily helpful.

What dcpd said.

quote:

Originally posted by dpcd:
Here is the non technical answer: Why are you measuring headspace of a cartridge? it has no meaning unless paired with the actual dimensions of your chamber. If you fired the brass in your rifle and it fits back in after you neck size it; it is good. If you have a target rifle that give a slight "feel" on the bolt closing, that is good. For a DG or big game rifle, give it a bit more clearance to insure no hangups in the field. Too much data is not necessarily helpful.

Yes.....but I know what my C/L at the shoulder datum measures on all of my rifles brass.

Too much data....no

I have one odd rifle.....it has a very short chamber. How do I know this? Because I measured the once fired brass at the C/L datum.....I didn't just guess....some do, I won't and will loose no sleep over doing so

There are really 2 answers for the 2 different calibers because 1 is belted and 1 is unbelted. The reason is the belted case will have a lot more expansion before it is fully expanded to fit your chamber

For instance, using the Hornady gauge and neck sizing only a typical string of measurements might be

30-06

new case - 2.040" (zero caliper with Hornady at 2" with gauge attached and then subtract that 2" for true measurement)
once fired - 2.0485" (neck sized)
twice fired - 2.050" (slight crush fit, neck sized)
3 times fired - 2.0510" (crush fit, time to push shoulder back to 2.050" for slight crush fit)

TOTAL expansion .011"

Belted case 300 win mag

new case - 2.253"
once fired - 2.270" (neck sized)
twice fired - 2.272" (slight crush fit, neck sized)
3 times fired - 2.2725" (crush fit, time to push shoulder back)

TOTAL expansion .0195"

So you really do not know your chamber headspace until you fire enough to get a crush fit. Now if you size a case, say once fired, then you could balloon the shoulder forward when you squeeze the case body. To see if you are doing this, take a measurement before you size and after you size. Then after you size, try the case in your rifle to see if you are getting a crush fit.

Simple answer, no the measurement on a once fired case is not the headspace of your chamber

Whether you use tools and gauges to measure or your rifle to measure, you are still measuring. Some people seem to think that if the method doesn't provide a number with a unit after it it is not a measurement. In fact it is. If you measure with the rifle, ideally remove the firing pin from the bolt so that you have good feel when closing on the action on the sized case.

Generally the gauges recommend sizing your cases to measure the same as once fired, as I recall. So if you size you want it to measure in your example 1.555 (I don't know what this number should be, just using your figures as an example).

If you then have many times fired brass that measures 1.557 for example, you want to be sizing it back to 1.555.

That is the theory.

By the way, if you "load it again" you may be bumping the shoulder anyway without realising it, depending on how your dies are set up, so measuring helps with that too.

I believe in measuring, so to each their own. DPCD is absolutely correct, but "a bit more clearance" doesn't mean the same to everyone. You can use the measurements of the threads of your dies to gauge how much that "more" is, but it is a lot easier to just measure it. If that "bit more" becomes "too much more" it costs you in brass life from oversizing.

I like at least 2 and not more than 3 thou sizing on a properly fireformed case in a bolt gun. On a DG rifle it would be more like 3 to 4 thou and I would feed all of my cartridges prior to venturing into the bush to check function.

Neck size your cartridges a fogetaboutit!!!

We DO say FUGETABOUTIT here in the big city

quote:

Originally posted by Leopardtrack:
We DO say FUGETABOUTIT here in the big city

Ehhh FUGETABOUTIT!!!!