Using Hornady Headspace Gauge to determine proper .223/5.56 headspace

[Kasteel]

So, I recently took delivery of a Hornady Lock-N-Load Headspace Guage set to help me out with measuring the headspace of my 5.56 and .223 reloads more precisely.

My goal: take once-fired cases from an unknown group of rifles (say military or civilian ranges) and process the cases such that they will safely and reliably chamber, fire, function and extract (manually when necessary) from any appropriately chambered firearm (usually AR-type), always assuming the firearm is within spec.

I spent a couple of days looking at various dimensional drawings of .223 and 5.56 chambers and cartridges to get familiar with specs. I also spent some time getting used to the Hornady gauge measuring once-fired cases, resized cases that that tended to stick in some chambers due to (apparently) incorrectly adjusted dies, and resized cases that ran through chambers well.

I also took measurements of some factory ammo (Federal 69gr. BTHP Match .223) for comparison.

Here are some of my measurements:

Cases from the "problem" group that will chamber and fire, but will stick pretty badly upon attempts to manually extract a round from the chamber: 1.460"

Cases that chamber and extract from multiple guns smoothly: 1.440"

Federal factory ammo: 1.457"

My question: exactly what is the accepted headspace standard for ammunition that has sufficient headspace as to ensure easy chambering and manual extraction of an unfired round when necessary, but not so much so as to prevent the firing pin from getting a solid hit on the primer?

In other words what is the max/min cartridge case dimension that I should be looking to measure?

[Kasteel]

In cruising around the Internet, my likely candidates for min/max cartridge measurement for headspace:

One guy sized brass for his Wylde chamber at 1.420"

The smallest chamber headspace measurement I found, for the Wylde chamber: 1.4316 (base to shoulder). The largest base to shoulder measurement was for the Clymer NATO chamber at 1.4380".

Several posts suggesting that minimum .223 cartridge headspace dimension is 1.4596" and max is 1.4666-.0070"

As mentioned above, my no-exception-smooth-functioning cases measured 1.440" and my measurement of the Federal factory ammo was 1.457".

[al503]

I'm a relative AR newbie and I'm not sure if this is the proper method but this is what I did.

I shot a handful of new factory rounds from both of my ARs. I measured the headspace with the hornady tool. I can't remember the exact figure but they were within .001" of each other. Based on the info found here (for semi auto rifles), I size the cases, pushing the headspace back an additional .004 to .005" As noted in the other thread, the bottom of my Dillon die has about a .025" gap with the shellplate when bottomed out.

I was worried that the base of the brass wouldn't get sized down enough but the reloaded cases make a nice 'thunk' when dropped in a JP case gauge and no issues when shooting the ammo.

[Kasteel]

As I understand it, your method is the preferred method to use when you are attempting to minimize work-hardening and wear and tear (by over working) brass you will shoot primarily in one rifle. Sound method.

I'm aiming more to ensure reliable function in a variety of rifles.

[Kasteel]

I think that method would also yield a bit better accuracy, all things being equal, but haven't done or seen any testing on it.

[Loop51]

As I understand it, your method is the preferred method to use when you are attempting to minimize work-hardening and wear and tear (by over working) brass you will shoot primarily in one rifle. Sound method.

I'm aiming more to ensure reliable function in a variety of rifles.

If you are trying to find a method of sizing to ensure proper function in multiple rifles, you would need to find a common headstamp ammo to do a little test with. First, measure your control ammo's current headspace as you have already done and record it. Fire a round through each of the rifles in question, noting which case came from which rifle.

Then re-measure the headspace on those cases. In order to ensure your ammo runs in any of those rifles, I would think you could take the one with the least growth, bump it back .004-.005" and use that measurement for your sizing. Test fire your newly resized case through all rifle to ensure proper function.

This may cause some brass to get worked pretty hard depending on how much some of them allow fired cases to grow but you would need to find a lest common denominator and this is one way to do it.

This method would be to ensure they fire in all rifle you own. If you want to be 100% sure it will function in any AR, your only real option is to return the brass to factory dimensions which will probably work the brass pretty hard. For me, this isnt a need so I just make sure it works in all MY rifles...

[Kasteel]

Right. I am looking for commonly used factory dimension.

[Kasteel]

Some measurements for reference:

Some of my own 55 gr. FMJ reloads using a couple of my guns to check for smooth chambering and extraction:

1.450"-1.457" The variance is probably due to adjusting die to get a length that worked.

Wolf 55 gr. Steel Case

1.453"-1.454" (measured five rounds)

Remington 55 gr. FMJ

1.458"-1.4585" (measured five rounds)

Remington 45 gr. JHP

1.4565"-1.458" (measured five rounds)

[Kasteel]

After some experimenting, I'm finding that rounds with the shoulder bumped back to 1.457" are good to go: they extract manually without undue resistance. I experienced more resistance the less I bumped the shoulder back. Rounds at 1.458"-1.459" stuck a bit, but would generally extract without need to "mortar" the gun. Starting at about 1.460" resistance was bad, and required mortaring and a solid thump to extract the round.

So, for me, 1.457" is max.

My question: does anyone know where the minimum is, beyond which unreliable ignition a possiblity? Are there any other issues that may occur with too much shoulder bump?

[cautery]

I don't know about unreliable ignition, but SAAMI specs only give a TOTAL of 0.010" between minimum and maximum headspace from the DL.

So personally, I would reject any case that headspaced more than 0.010" from the measured headspace on MY chamber. As you are going for multiple gun reliability, I would set the measurement at 0.010" max based on the seepest chamber I had...

[cautery]

I'm going out to shoot my rifle tomorrow to get fired cases for analysis.... But I noticed something today that is WEIRD.

I was setting up my Redding sizing die to get it close (pending tomorrow), and I used my Redding Instant Indicator (set up to minimum SAAMI specs using the supplied gauge) to check the amount of sizing. <long story omitted>

I ran a cleaned/fired case in the indicator that had not been decapped or sized and discovered that it BARELY met the MINIMUM SAAMI specs for headspacing... Is this unusual for military brass that has been fired?

To process this brass, I guess I'll set the die to the point just prior to touching the shoulder so it sizes the body, decaps, and runs the neck expander through the mouth. ???

[Kasteel]

I'm soooo glad I'm not the only one who experiences weirdness. I'll look forward to your update--and thanks for you input!!

[cautery]

I'm soooo glad I'm not the only one who experiences weirdness. I'll look forward to your update--and thanks for you input!!

Your welcome... for what, I'm not sure, but I'm glad to keep you company on the road to reloading for rifle... competently.

[Kasteel]

By the way, if possible, I'd love to know the actual base to shoulder measurement in the case you checked

[cautery]

I can't give you that.... The Instant Indicator measures true headspace from the base to the Datum Line, which for 223 is the point ON the shoulder where the body diameter is 0.330" (pretty sure of that number). It's just some random once-fired 223 we got a long time ago... No idea where it came from... it's possible that it was picked up on an IPSC/USPSA range after a match... which might well explain the well-manicured military brass...

[kamikaze1a]

Are you using the Hornady gauge to arrive at those figures?

If you want your rounds to chamber in any chamber, you need a case gauge. That Hornady tool is not a case gauge...it measures changes between datum line (reference point) on the shoulder to the base.

Edited August 24, 2013 by kamikaze1a

[Kasteel]

Yeah. Well, a case gauge can present problems of its own:

http://www.brianenos.com/forums/index.php?showtopic=179160&hl=

I can see a place for the use of both tools in conjunction--in this situation, to determine whether a shoulder has been bumped back too far.

[kamikaze1a]

You are right. The case gauge is not always the answer as I have seen rounds that check out in the case gauge but stick in a chamber.

The point I am trying to make is that the "headspace gauge" you have is designed to compare or determine the amount the shoulder has been bumped back using a reference point on the shoulder. Being that the "A" bushing is universal to multiple rounds, unless it was designed around 223/556 specs, it could not measure but rather it compares. Using this tool and bumping back the shoulder .00X means that you bumped back according to the chamber it was fired in, not necessarily to specs. A case gauge "should" be to industry specs...

By the way, I followed your link and you are sure having issues. Have you tried more than one brand of case gauge?

[Dan Sierpina]

I've been following the two similar threads, this one and the one by Clay Autery. It seems that all the tools available are making people question what the heck is to be done.

I've been an R&D machinist for over 40 years. This isn't rocket science, and a couple thousandths of space won't have AR parts strewn over the countryside.

I've been playing with AR's since before the plethora of parts that we now have available. I've machined barrel blanks and chambered them for AR's. Not just tighten a barrel nut and said that I've "built" an AR.

I use a Clymer .223 Rem Go gage to set my dies. I use a bushing, to take a measurement over the gage, the inside diameter doesn't mean squat, as long as you use the same bushing for all measuring. I set my sizing die to bump the shoulder back .002 under the dimension that I got from the chambering headspace gage, and size all my brass that way.

One of my AR's has a barrel that I machined and chambered, and the bolt would just rotate into battery when it was new. The brass fits in all 5 or 6 AR's in the safe, no issues.

Now, not trimming brass, and mushrooming the shoulder slightly has caused more problems than not bumping the shoulder back enough.

I hope this helped.

[cautery]

I've been following the two similar threads, this one and the one by Clay Autery. It seems that all the tools available are making people question what the heck is to be done.

I've been an R&D machinist for over 40 years. This isn't rocket science, and a couple thousandths of space won't have AR parts strewn over the countryside.

I've been playing with AR's since before the plethora of parts that we now have available. I've machined barrel blanks and chambered them for AR's. Not just tighten a barrel nut and said that I've "built" an AR.

I use a Clymer .223 Rem Go gage to set my dies. I use a bushing, to take a measurement over the gage, the inside diameter doesn't mean squat, as long as you use the same bushing for all measuring. I set my sizing die to bump the shoulder back .002 under the dimension that I got from the chambering headspace gage, and size all my brass that way.

One of my AR's has a barrel that I machined and chambered, and the bolt would just rotate into battery when it was new. The brass fits in all 5 or 6 AR's in the safe, no issues.

Now, not trimming brass, and mushrooming the shoulder slightly has caused more problems than not bumping the shoulder back enough.

I hope this helped.

Thanks, Dan.

[kamikaze1a]

WOW...I went and read the other thread in it's entirety. Very odd...

Did you check your brass for collapsed shoulder. Probably not that since you said it sticks with sized brass without bullets. Another thing might be trying different sizer die?

As was mentioned excess sizing or setting the shoulder back too far could result in case stretching and case head separation. Using your Hornady tool, could you compare before firing to after? It would be interesting to see how much your brass stretches with the case gauge showing that much setback. Excessive sizing and then stretching will lead to poor brass life and you may see a bright ring a little over 1/2" up from the base. Or wondering if the gauge is out of spec?

Regarding cam over, it is more of an issue with progressive presses than single stage presses. With a progressive press, the cam'd over die torques the ram/plate where as with a single stage the force is inline with the ram so no torquing.

[Kasteel]

Yes. Now we're getting some big brains (i.e. bigger than mine) in on this act. I'll get to answering some questions to the best of my limited ability on my days off starting tomorrow evening. For now, I'm just loving the BE forums.

For now Kamikaze: as far as the issue goes, I'm really being a bit OCD in the view of lots of reasonable folks. The rounds that measure greater than 1.457" will function just fine under most circumstances. As long as you don't need to manually extract an unfired round from a cold chamber, you might never even know there was an issue.

The one "practical" issue I've run across is firing ammo that is 1.458+" (probably 1.46+") in a 14.5" DD mid-length barrel. In this rifle, the bolt failed (on occasion) to travel sufficiently far to the rear to pick up another round, resulting in a failure to feed.

The added "oomph" necessary for the BCG to extract the insufficiently shoulder-bumped cartridge might account for this.

Might. I have, to my dismay, proven that I am an idiot. Or a Murphy magnet.

More to follow.

[bigedp51]

I was very lucky to be at the range when our local Police and SWAT teams were practicing and came home with three five gallon buckets of .223/5.56 brass. The brass was fired in many, many different types and models of the AR15 rifle and some of you are way over thinking this resizing issue.

I'm loading for three diffrent AR15 rifles and a bolt action .223.

1. All the range pickup brass was resized first in a RCBS small base die, and please take note this "small Base" die only made the case .0005 smaller in diameter at the base than a standard die. A small base die simply sizes further down the case than a standard die. I used the small base die for several reasons, "a" not all the chambers the ammo was fired in were the same size/dimension "b" not all the brass was made by the same manufacture and cartridge cases have different spring-back rates. "c" the small base die returns the cases to minimum size standards.

2. All the cases were sized to minimum with the die making hard contact with the shell holder and the press set to cam over or maximum shoulder bump.

3. After these case were fired in my AR rifles a Hornady cartridge case headspace gauge was used to measure "fired" case length. These lengths were compared to unfired military 5.56 Lake City cases and commercial .223 cases.

4. After experimenting with resized lengths I decided to use the Redding competition shell holder .004 taller than a standard shell holder. The resized cases are .001 to .002 longer than the average new case length when resized and function 100% in all my AR15 rifles. This means I have .004 to .005 head clearance in all the chambers and there is no stretching and thinning in the web area of the case.

I will now tell you a funny story I read at the "The Rifleman's Journal" and this statement was made by a well known competitive shooter. "I get my best accuracy when the case fits the chamber like a rat turd in a violin case"

Edited August 26, 2013 by bigedp51

[Kasteel]

Overthinking? Really?

Please explain.

"2. All the cases were sized to minimum with the die making hard contact with the shell holder and the press set to cam over or maximum shoulder bump."

Maximum? Minimum? Ok. SAAMI max/min? For which chamber? What, exactly, is the measurement to which you refer?

"3. After these case were fired in my AR rifles a Hornady cartridge case headspace gauge was used to measure "fired" case length. These lengths were compared to unfired military 5.56 Lake City cases and commercial .223 cases."

And these measurements were . . . . ? This would be fantastic info.

"4. After experimenting with resized lengths I decided to use the Redding competition shell holder .004 taller than a standard shell holder. The resized cases are .001 to .002 longer than the average new case length when resized and function 100% in all my AR15 rifles. This means I have .004 to .005 head clearance in all the chambers and there is no stretching and thinning in the web area of the case."

And average case length was?? Chamber measurements??

You are in danger of actually contributing some very useful information. Please hold forth sir.

Seriously, you've got some good stuff there. And, as to the original question: how much shoulder bump is too much?

Anything? Anyone?

[Kasteel]

Also, when you say all the rounds function fine, I'm assuming you include manual extraction of an unfired round?