Why is .223 headspace in 10,000ths?

[aquinas]

New to .223 handloading and was wondering why it's quoted as 1.4636 to 1.4736?

Take .308 for example, SAAMI headspace is 1.630 to 1.640. Simple.

Can I measure it as 1.463 to 1.473 and disregard the 6/10,000?

Do I need a caliper that measures to ten thousandths?

 

[Clark]

Re: Why is .223 headspace in 10,000ths?

Remington registered the drawing with SAAMI.
It says the chamber should be between 1.4636 and 1.4736", = a .0100" range.
It says the cartridge should be between 1.4596 and 1.4666", = a .0070" range.

There is .0030" of overlap.

I have a Ruger #1V 223 that is .003" more headspace than minumum.
I have a Bushmaster V-match 223 that is .008" more headspace than minimum.
I have a Colt AR15 223 that is .005" more headspace than minimum.
I have a Wilson AR15 223 that is .0065" more headspace than minimum.
I have a Mauser 223 [that I cut the chamber] that is .008" more headpace than minimum.

I try to keep brass that comes out of a rifle to stay with that rifle.
That way the brass from the bolt action and falling block get neck sized and the brass from the AR15s gets full length resized with the die adjusted to push the shoulder back to .001" clearance in the chamber.

I don't have a sizer die associated with every AR15 [maybe I should], so I have to adjust it nearly every time I use it, so some brass gets sized wrong while I am adjusting it.

What does it all mean?
For handloading, it does not matter what SAAMI says, what matters is what your rifle is.

 

[Fuzzball]

Re: Why is .223 headspace in 10,000ths?

"Can I measure it as 1.463 to 1.473 and disregard the 6/10,000?"

NO! If you do it that way your front swivel ring will rust!

Well, actually, I don't know how you would measure headspace to that resolution or why you would even wish to; it really only matters to makers and gunsmiths. All a reloader needs is how to make his ammo fit his chamber well enough to seat consistanly and without excessive stretching each time it's fired. THAT can be done without a measurement tool at all.

 

[aquinas]

Re: Why is .223 headspace in 10,000ths?

How?

 

[Fuzzball]

Re: Why is .223 headspace in 10,000ths?

"How?"

Okay. But if you don't read this after all the typing I'm gonna be ticked.

It really doesn't precisely matter what the chamber size really is, we have to live with it as it is. You know a fired case will easily drop back in the chamber and the action will close on it. FL sizing squeezes the case sides and that squewze forces the shoulder forward a few thousanths. All we need do is keep the shoulder where it was after resizing and springing back a little. We have two ways of putting the shoulder back were it was after firing, and that IS as far as it needs to go back!

We can measure the head-to-shoulder length before sizing and then push it back there during sizing. For that, we can use a calibrated gage like the Hornady LnL and/or Sinclair and a caliper. Or we can use the RCBS Precision Case Mic or The Innovative Technologies dial indicator type gages; all of them do the same thing for us. How it's calibrated means nothing to us, all we need is a relitive measurement of 'this' to 'that', fired to sized. IF I had a stable full of the same cartridge I would certainly have one of the calibrated gages to work with. I think you would do better with the RCBS Case Mic because it is totally repeatable between uses while the others usually are not. Make your self a note for what each of those chambers needs and keep it in the gage box so you can easily reset your FL die for what you're loading for.

What you ask is the "no cost-no numbers" way. First, back the sizer up a quarter turn from fully down (about 15 thousants UP from 'full' sizing) and size a case, checking for chambering afterwards - it probably won't go. Turn the die down in steps of 1/16th turn (about 4.5 thou) until you can close the action freely for an auto or with just a touch of resistance with a bolt. If you go too far enough and the action closes too easily, back off half the distance and size another case to confirm. This is the way all of us did it until fairly recently, we had nothing else to use but our chambers.

For precision work, forget any of the 'drop-in' type cartridge case gages. They can only tell us if the case will work in any weapon ever made for the cartridge - in other words, if it's back to factory dimensions, which is only helpful if you are swapping the ammo around. One of the greatest values in handloading is that we can custom fit our ammo to what we are actually shooting and using a SAAMI cartridge drop-in gage defeats that.

Note that the SAAMI drawing above shows the full max-min cartridge shoulder range for the .223 is 7 thou; in fact, that's the most common tolerance for bottle neck cartridges. It's EASY to overshoot when resizing and create excess "headspace" when there should be none. So, keep your die changes small. I often get appalled when someone suggests making "small die changes like 1/4 turn ...." Goodness! That's some 15 thou per step and is more than twice the full headspace tolerance range!

Cartridge brass is 'springy' and inconsistant. It will spring back down a little when fired and it will spring back up a little when sized. The actual amount of spring back is determined by the alloy AND how much many times that case has been cycled. We will NEVER get repeatable precision between cases so we learn to live with a variation of around 2-3 thou even with the same box of cases when FL sizing. Thus, dreaming of a caliper that could accurately read to +/- .0001" would gain us nothing at all even if it could be bought. Fortunately, we don't need that, we just need to make the longest resized head-to-shoulder equal to or a tad shorter than our chamber and all will be well.

Last point, as an aside that you did't ask; neck sizing doesn't always produce better accuracy or case life than FL sizing done right. Most properly resized cases fail from neck splits and the average neck die will do that as soon as the average FL die. Only way to extend case neck life much is to anneal after each few loading cycles and not a lot of people want to bother with that because it's hard to do it very well.

 

[aquinas]

Re: Why is .223 headspace in 10,000ths?

Fuzzball...I'm a very experienced handloader. Nice post but you didn't have to go there.

I only want to know why .223 goes to ten thousandths while most others are measured in thousandths?

As far as size until it fits the chamber, I know you can do that but it isn't a good approach. I want a number. To get that, I take a minimum Forster headspace gauge and zero it in a hornady headspace gauge. Measure a case. It comes up -.002 and I'm good to go.

Most of my chambers (that I'm currently shooting) are minimum SAAMI specs. I keep up with them as they grow and adjust accordingly.

Again, the question: why is .223 measured in ten thousandths? If you can answer it, fine. But don't hijack the thread with a bunch of stuff that wasn't asked for.

 

[plastikosmd]

Re: Why is .223 headspace in 10,000ths?

Thx fuzz, I copied that and filed it

 

[groovinpickle]

Re: Why is .223 headspace in 10,000ths?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">But don't hijack the thread with a bunch of stuff that wasn't asked for.</div></div>
To be fair, wasn't Fuzzball answering your question?

 

[Teggy1]

Re: Why is .223 headspace in 10,000ths?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">

You're "very experienced" and need to ask how?

Then shit on the guy that is explaining it to you, by asking not to hijack the thread?

His explanation says NO you don't need to buy tools that measure to 1/10,000ths. Guess you didn't read it, or understand it for that matter.

By the way, good explanation Fuzzball.

 

[aquinas]

Re: Why is .223 headspace in 10,000ths?

Never teach a pig to sing.

It wastes your time and it annoys the pig.

 

[aquinas]

Re: Why is .223 headspace in 10,000ths?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Teggy1</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">

Yeah, because I thought maybe he had some other way I didn't know about.

 

[MitchAlsup]

Re: Why is .223 headspace in 10,000ths?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">I only want to know why .223 goes to ten thousandths while most others are measured in thousandths?</div></div>

Because that was what the numbers were on the dimension sheet when it was sent to SAAMI.

 

[pjparker]

Re: Why is .223 headspace in 10,000ths?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Fuzzball</div><div class="ubbcode-body">"Can I measure it as 1.463 to 1.473 and disregard the 6/10,000?"

NO! If you do it that way your front swivel ring will rust!

</div></div>


My .223 does not have a front swivel ring - Will it rust anyway ?

 

[aquinas]

Re: Why is .223 headspace in 10,000ths?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: himaster</div><div class="ubbcode-body">I only want to know why .223 goes to ten thousandths while most others are measured in thousandths?</div></div>

Because that was what the numbers were on the dimension sheet when it was sent to SAAMI. </div></div>

Finally...an answer!

 

[Fuzzball]

Re: Why is .223 headspace in 10,000ths?

"Yeah, because I thought maybe he had some other way I didn't know about."

Given your initial basically pointless noob type question and then the "How", I didn't have a clue what you did or didn't know about. Excuse me for not recognising your expertise and I apologise for hijacking your thread.

 

[aquinas]

Re: Why is .223 headspace in 10,000ths?

14 posts and still no answer.

Fuzzball...I wasn't being a jackass. I just call 'em as I see em. I'm straightforward and speak my mind.

I thanked you for the post.

 

[Fuzzball]

Re: Why is .223 headspace in 10,000ths?

"14 posts and still no answer."

Perhaps because there IS no specific answer to a meaningless question?


"Fuzzball...I wasn't being a jackass. I just call 'em as I see em. I'm straightforward and speak my mind."

So do, I usually, or what there is of my mind. But sometimes both common courtesy and common sense makes me refrain so I won't look like a jackass... other people may not be able to tell the difference between a jackass and someone who only looks like a jackass.


"I thanked you for the post."

You're very welcome, even tho the long effort was unacceptable to you.

 

[felderthewelder]

Re: Why is .223 headspace in 10,000ths?

Oh my Jesus. The drama.