All about Headspace - I'm not sure where I stand here?

[SinWolf]

Good day all,

Rifle: Tikka T3
Caliber: 30-06
Twist: 1-11
Barrel length: 565mm (22.2441")

Disclaimer: Please bare with me, as I'm sure I did not always use the right terminology with this post, but I'm sure (and hope) it makes sense

Ok... So I've been doing some research the last couple of months regarding headspace.

I have NEVER FL sized any of my reloads, ONLY neck size... I bought brown box PMP rounds, shot them out at the range, and so I have acquired my once fired brass for reloading, which was also now fire formed. These were then always neck sized only...

I want to change my reloading practice to now always do FL sizing. The consensus (it seems) is to FL size, but only bump shoulder 0.001" to 0.002" (0.025 - 0.05mm) to minimize brass wear.

Ok... So how I understand it is that your chamber has a headspace measurement of x

After re-using the same brass over and over, with no FL sizing, the brass will grow to a point where the brass headspace measurement will be x + y - This is when your bolt needs more pressure to close...

You want to FL size your brass to have a headspace measurement of x - 0.002" (0.002" = 0.05mm)

There is also a SAAMI spec for headspace, but this is obviously difficult to use, as we use comparators, and not the actual values. It will be difficult to convert our values to an "actual" value, as not all comparators are equal. The only way to do this would be to have a SAAMI spec case and measure with your comparator, and this obviously is not something you can buy over the counter. But this is also not needed in my opinion, but one would think that brass manufacturers would at least adhere to these SAAMI specs when they produce new brass (see Lapua brass measurements later in this post)?

Now all this theory makes sense... But when I start with measurements, things does not make sense anymore...

Ok, firstly, I started with x, I measured my firearm headspace (with Hornady comparator) as 51.89mm

My method for measuring my rifle headspace... I took a case, FL sized it and took the shoulder back as much as my die would allow. The case headspace measured 51.82mm (and this makes sense, as the case headspace should measure shorter than the chamber after a full length resize). I then took a spent primer (one that was removed during a de-priming session) and pushed it in the primer pocket with my finger. You can actually only get it in about 1/3rd of the way.... I then carefully closed the bolt. The bolt pushes the case forward until the case head meets the chamber, and then the bolt pushes the primer into the pocket to a point where the bolt can close. Now carefully remove the case and measure your headspace against the primer that is not fully seated inside the primer cup.

Ok... so back to my findings...

My PMP brass, that have seen probably around 8 firings gave me the following measurements:

51.85
51.86
51.87
51.85
51.86
51.83
51.84
51.82
51.83

Now, these measurements do not mean much, because I have never measured the headspace on a new brown box PMP round, and I don't have any rounds on me to measure. But what does bother me, is why are all of them shorter than x, 51.89mm ?? All sources that I can remember said that these would probably be longer than x after a few firings without bumping shoulders back with each reload?

I have some ONCE fired (according to my reloading procedures, once fired PMP brass = NEW brass

) PMP brass, and they measured as follows:

51.83
51.84
51.83
51.83
51.83
51.83
51.83
51.83
51.82

Clearly, the once fired brass is more consistent at this stage, but still well under x.

So if I were to use the once fired, do I then FL size without bumping shoulders? But just FL sizing, without touching the shoulder increases the cartridge headspace again... Should I set up my die to try and end with a case headspace of x - 0.002", in other words 51.89mm - 0.05mm = 51.84 mm?

Ok, so that was PART 1...

Now for PART 2...

So I thought I need to step up my reloads' consistency... Maybe move away from the old PMP brass....

So I ordered 100 Lapua cases, as they are the best right? They are the most expensive! And consistent... And most sources on the net recon you can just load them up and fire away, no prep needed!!

Glen Zediker (in his book: Top Grade Ammo) makes it very clear that even new brass needs to be processed and sized before use... And now I can see why...

So here are 20 Lapua cases, brand new, measured headspace:

51.88
51.88
51.84
51.86
51.84
51.85
51.83
51.84
51.88
51.85
51.84
51.86
51.83
51.84
51.85
51.90
51.85
51.84
51.94
51.87

So I took that 51.94, tried it in the rifle, and yes, the bolt is very difficult to close, that headspace is too long...

I'm surprised at these measurements, they are all over the place... And that is why I mentioned SAAMI earlier in the post, should the new Lapua brass not at least meet SAAMI requirements??

So this now comes back to my FL sizing question... What headspace should I aim for when resizing these new Lapua cases?

So now I "aim" for a certain headspace measurement when doing FL sizing... That is all good and well... lets say we aim for the 51.84mm

But the next step after resizing is to open the case mouth with an expander mandrel die (I'm moving away from the FL die's button expander, as the consensus seems to be that this type of expander contributes to run-out).

But irrespective of the method you use to open the mouth, this has an influence on your headspace measurement again... The expander mandrel puts downward forces on the case, and then you end up with a case headspace of 51.44mm - a
The expander ball inside the FL die will have a pulling force on your case, and then you end up with a case headspace of 51.44mm + a

Then, seating a bullet puts a downward pressure on the case again...

So how do you make sure you end up with the correct headspace? Or am I making it too technical ??

 

[KY_Windage]

I think you are making it too technical.

Put in empty brass until you find the length where there is resistence to the bolt closing, measure it with your comparator, then set your FL die to reset the shoulders back to .003" shorter.

You may need to tweak that a bit once you have some loaded cartridges. If there is resistence to closing, set back a bit more. Be sure your necks are not too long, or your bullets seated too high, both of which will also produce resistance to closing.

Some brass will take several firings and still never move the shoulder out to where your die is doing anything. They will not be your most accurate rounds, most likely.

Welcome to the anal-retentive world!

 

[Patriot007]

Good day all,

Rifle: Tikka T3
Caliber: 30-06
Twist: 1-11
Barrel length: 565mm (22.2441")

Disclaimer: Please bare with me, as I'm sure I did not always use the right terminology with this post, but I'm sure (and hope) it makes sense

Ok... So I've been doing some research the last couple of months regarding headspace.

I have NEVER FL sized any of my reloads, ONLY neck size... I bought brown box PMP rounds, shot them out at the range, and so I have acquired my once fired brass for reloading, which was also now fire formed. These were then always neck sized only...

I want to change my reloading practice to now always do FL sizing. The consensus (it seems) is to FL size, but only bump shoulder 0.001" to 0.002" (0.025 - 0.05mm) to minimize brass wear.

Ok... So how I understand it is that your chamber has a headspace measurement of x

After re-using the same brass over and over, with no FL sizing, the brass will grow to a point where the brass headspace measurement will be x + y - This is when your bolt needs more pressure to close...

You want to FL size your brass to have a headspace measurement of x - 0.002" (0.002" = 0.05mm)

There is also a SAAMI spec for headspace, but this is obviously difficult to use, as we use comparators, and not the actual values. It will be difficult to convert our values to an "actual" value, as not all comparators are equal. The only way to do this would be to have a SAAMI spec case and measure with your comparator, and this obviously is not something you can buy over the counter. But this is also not needed in my opinion, but one would think that brass manufacturers would at least adhere to these SAAMI specs when they produce new brass (see Lapua brass measurements later in this post)?

Now all this theory makes sense... But when I start with measurements, things does not make sense anymore...

Ok, firstly, I started with x, I measured my firearm headspace (with Hornady comparator) as 51.89mm

My method for measuring my rifle headspace... I took a case, FL sized it and took the shoulder back as much as my die would allow. The case headspace measured 51.82mm (and this makes sense, as the case headspace should measure shorter than the chamber after a full length resize). I then took a spent primer (one that was removed during a de-priming session) and pushed it in the primer pocket with my finger. You can actually only get it in about 1/3rd of the way.... I then carefully closed the bolt. The bolt pushes the case forward until the case head meets the chamber, and then the bolt pushes the primer into the pocket to a point where the bolt can close. Now carefully remove the case and measure your headspace against the primer that is not fully seated inside the primer cup.

Ok... so back to my findings...

My PMP brass, that have seen probably around 8 firings gave me the following measurements:

51.85
51.86
51.87
51.85
51.86
51.83
51.84
51.82
51.83

Now, these measurements do not mean much, because I have never measured the headspace on a new brown box PMP round, and I don't have any rounds on me to measure. But what does bother me, is why are all of them shorter than x, 51.89mm ?? All sources that I can remember said that these would probably be longer than x after a few firings without bumping shoulders back with each reload?

I have some ONCE fired (according to my reloading procedures, once fired PMP brass = NEW brass

) PMP brass, and they measured as follows:

51.83
51.84
51.83
51.83
51.83
51.83
51.83
51.83
51.82

Clearly, the once fired brass is more consistent at this stage, but still well under x.

So if I were to use the once fired, do I then FL size without bumping shoulders? But just FL sizing, without touching the shoulder increases the cartridge headspace again... Should I set up my die to try and end with a case headspace of x - 0.002", in other words 51.89mm - 0.05mm = 51.84 mm?

Ok, so that was PART 1...

Now for PART 2...

So I thought I need to step up my reloads' consistency... Maybe move away from the old PMP brass....

So I ordered 100 Lapua cases, as they are the best right? They are the most expensive! And consistent... And most sources on the net recon you can just load them up and fire away, no prep needed!!

Glen Zediker (in his book: Top Grade Ammo) makes it very clear that even new brass needs to be processed and sized before use... And now I can see why...

So here are 20 Lapua cases, brand new, measured headspace:

51.88
51.88
51.84
51.86
51.84
51.85
51.83
51.84
51.88
51.85
51.84
51.86
51.83
51.84
51.85
51.90
51.85
51.84
51.94
51.87

So I took that 51.94, tried it in the rifle, and yes, the bolt is very difficult to close, that headspace is too long...

I'm surprised at these measurements, they are all over the place... And that is why I mentioned SAAMI earlier in the post, should the new Lapua brass not at least meet SAAMI requirements??

So this now comes back to my FL sizing question... What headspace should I aim for when resizing these new Lapua cases?

So now I "aim" for a certain headspace measurement when doing FL sizing... That is all good and well... lets say we aim for the 51.44mm

But the next step after resizing is to open the case mouth with an expander mandrel die (I'm moving away from the FL die's button expander, as the consensus seems to be that this type of expander contributes to run-out).

But irrespective of the method you use to open the mouth, this has an influence on your headspace measurement again... The expander mandrel puts downward forces on the case, and then you end up with a case headspace of 51.44mm - a
The expander ball inside the FL die will have a pulling force on your case, and then you end up with a case headspace of 51.44mm + a

Then, seating a bullet puts a downward pressure on the case again...

So how do you make sure you end up with the correct headspace? Or am I making it too technical ??

Really to technical. Take the expander ball and the hole top half of the FLS die, off. I use a Forster FLS die.
Take the fired brass that you just shot out of your rifle. DE prime it, Measure the head space and subtract 2 thousandths and set the FLS die up to bump the shoulder back 2thou,, just like you did with your bump die. Keep in mind that this will shrink your case neck down also,, all in one step. Then use your expander mandrel and expand the case neck to your desired neck size. Please use imperial sizing wax when expanding and do not use graphite to expand with.. People kill me when I see them using it as an expanding lube. ( Very,, counter productive and dirty.) Good Luck, and yes, It's that simple.
Don't forget to anneal after every firing also.

 

[Uncle Ed]

Don't over complicate your life, measure a fired case with your Hornady case headspace gauge. Now set the die up for a bolt action for .001 to .002 shoulder bump.

I would get a set of Redding competition shell holders that allows you to set the shoulder bump in .002 increments. And I would pause at the top of the ram stroke for a few seconds when sizing your cases. This minimizes brass spring back and makes your shoulder locations more uniform.

Headspace is also the distance between your ears, and I think you have been reading too many posts by F. Guffey.

When I first started reloading in 1973 I had a Rockchucker press, no gauges except for a worthless green plastic Lyman vernier caliper. I set my RCBS die up per the instructions and never had a case head separation. (shoulder bump and the internet had not been invented yet) I bought Hornady bullets and seated the bullets to the middle of the cannelure. The deer I shot didn't know I was a rookie reloader and still fell over dead when I shot them. And if your standing on your hind legs shooting at a deer running at top speed for some reason the bullets always hit behind the deer. So forget headspace and get faster bullets and aim three feet in front of the shoulder.

I didn't have any reloading problems until I came here, read all the postings and started buying all sorts of gauges, bushing dies, etc and started overthinking everything.

 

[Ol Thumper]

They’ve pretty much nailed it, Im going to try out the Redding competition shell holder sets pretty soon myself but don’t overthink the simplest of tasks. You confused me just trying to read that so I see why your confused

 

[LC Tikka]

The head space is the clearance to the bolt face, created once the shoulder is bumped back, eg 2 thou/.05mm. Not 51.8???
LC

 

[RegionRat]

To make this even more simple...
Since your once fired cases will still allow your bolt to close easy, and you have that data, you should try and use that data and that longer Lapua sample to establish your chamber size.

Being careful with that long Lapua case, since you only found one where the bolt doesn't want to close, carefully start with your FL die turned out where it has no effect and slowly approach the shoulder to try and catch the first sign of it changing the shoulder datum length.

Also use your chamber to verify that feel as well.

Using the very small changes slowly turn the die in to "bump" that shoulder datum down just the first little bit and chamber again while collecting the measurement data and taking notes. Continue till the dimension has changed just 0.001" - 0.002" (0.0254 - 0.0508 mm) . Along the way you may even find that the shoulder datum dimension climbs before it shrinks. This is not uncommon and depends on several variables including the brass and the chamber size compared to the die.

Once you have bumped that shoulder down as above, keep a record of the value and compare it to the earlier ones where the fired cases were still closing in the chamber without effort. You will eventually see them grow to the value and then get tight till they are bumped down where the bolt first closes easily.

You are just a few cycles short of getting a tight closure on those fired cases. It sometimes takes four or more cycles to establish the chamber size, but it can also happen in just two or three cycles depending on your brass, chamber, pressure, and luck.

ETA: Your concern about expander balls and mandrels also changing the shoulder datum on the case is not wrong. Expander balls being pulled back up can alter the shoulders in instances where there is too much cold working and not enough lube. An expander mandrel is less harsh, but you should also consider using lubrication to minimize the longitudinal force on the neck and shoulder. When done right, and expander mandrel will not significantly affect that shoulder length.

Good Luck and take lots of notes.

 

[SinWolf]

The head space is the clearance to the bolt face, created once the shoulder is bumped back, eg 2 thou/.05mm. Not 51.8???
LC

Yes, like I mentioned in the beginning of my post... Please excuse the terminology...

The 51.89mm is actually my chamber length...

Thanks for all the feedback everybody!! Much appreciated...

The fact that I now know my chamber length is 51.89mm... Should I not just use this measurement to establish my shoulder bump? Set up my die in such a way to end with a cartridge length of 51.89mm - 0.05mm = 51.84mm That way, I know I always have a headspace of 0.05mm...

 

[RegionRat]

If the bolt will not close or is tight to close at 51.89 mm, and it will close at 51.84 mm, then you are good to go.

On occasion, you may find that after you accumulate more cycles on that brass, that you begin to encounter tight closure again even though you have 51.84 mm on the shoulder. That might indicate the die needs to squeeze down just a little beyond 51.84 mm on the shoulder in order to also get the body diameters back down to size. Don't worry about this unless it happens, just be aware that the brass might still show you more changes after four or five cycles.

 

[LHSmith]

Overthinking it. I recommend to remove the firing pin spring assembly
from bolt to eliminate the pressure on the case from the spring. I prefer the tape method- add a layer(s) of thin (scotch) tape to the case head (without any primer) to come up with a H/S value ( the spent primer method results in inconsistent measurements.
As said it can take several firings to fully fireform brass- they'll measure differently before fully FF. And yes, when sizing -perform every operation exactly the same way (this also applies to every step in the process including test shooting).
You are being overwhelmed by numbers, use the tape method to start out then once you have cases that function well-then you can determine your H/S number. If your die is a good match to your chamber you should be good to go.

 

[hoz53]

Don't over complicate your life, measure a fired case with your Hornady case headspace gauge. Now set the die up for a bolt action for .001 to .002 shoulder bump.

I would get a set of Redding competition shell holders that allows you to set the shoulder bump in .002 increments. And I would pause at the top of the ram stroke for a few seconds when sizing your cases. This minimizes brass spring back and makes your shoulder locations more uniform.

Headspace is also the distance between your ears, and I think you have been reading too many posts by F. Guffey.

When I first started reloading in 1973 I had a Rockchucker press, no gauges except for a worthless green plastic Lyman vernier caliper. I set my RCBS die up per the instructions and never had a case head separation. (shoulder bump and the internet had not been invented yet) I bought Hornady bullets and seated the bullets to the middle of the cannelure. The deer I shot didn't know I was a rookie reloader and still fell over dead when I shot them. And if your standing on your hind legs shooting at a deer running at top speed for some reason the bullets always hit behind the deer. So forget headspace and get faster bullets and aim three feet in front of the shoulder.

I didn't have any reloading problems until I came here, read all the postings and started buying all sorts of gauges, bushing dies, etc and started overthinking everything.

LOL. i was thinking when i read the heading to this thread " Where is the Guffer when ya need him"

 

[LHSmith]

I will add -there is nothing wrong with having 0.003 H/S. I know competitors who target 2-3 thou to minimize bolt operation effort. It does not take much dirt to hamper smooth operation.

 

[BDman]

51.84 is where I'd start. You mentioned 51.44 later in your post but I think you meant 51.84. You can try a longer length but, you need to strip your bolt to ensure your getting the true "feel" for when they are too long.

 

[dgeesaman]

But the next step after resizing is to open the case mouth with an expander mandrel die (I'm moving away from the FL die's button expander, as the consensus seems to be that this type of expander contributes to run-out).

But irrespective of the method you use to open the mouth, this has an influence on your headspace measurement again... The expander mandrel puts downward forces on the case, and then you end up with a case headspace of 51.44mm - a
The expander ball inside the FL die will have a pulling force on your case, and then you end up with a case headspace of 51.44mm + a

Then, seating a bullet puts a downward pressure on the case again...

It sounds like you’ve got the chamber vs brass headspace under control.

The shoulder bump / headspace length of the brass should not change during neck expansion or bullet seating. Those operations should feel smooth and steady pressure, without forcing or grabbing.

Brass is not like lead - it has some springiness that means it will support some force before it permanently deforms. The seating and external expander should be well away from permanent deformation.

Internal expander balls can drag hard so those might affect headspace in some situations. I consider that to be highly undesirable.

David

 

[CharlieNC]

The primer method has always given me accurate zero headspace measurements. I have compared this to brass plus .002" thick layer tape to assure it works. Several of your results are not within the distribution, and you may want to repeat this a few times with different make brass as well to assure yourself. This zero HS minus desired clearance (eg .002 ) is the reference for sizing, vs bumping from a variable fired brass of which you have no idea how it fits the chamber.

 

[std7mag]

If your headspace in the chamber is "X", then the brass can only grow to "X".
Your brass cartridge is not going to push the steel chamber.

 

[JFrank]

OR..just get a Wilson case gage and forget all the complicated stuff or better yet a cut away Sheridan gage.

 

[Coyotefurharvester]

Also your measurements seem to be in the range of when I have rotated a case in the comparator body. Factory chambers seldom produce fired brass that gives the same measurements all the way around. Bolt face not perfectly square to chamber, brass doesn't push forward equally around the shoulder, brass shoulder thickness varies. The comparator isn't perfect either, I mark mine so I put it in the adapter the same each time.

 

[searcher]

To simplify things - you always want to set your shoulders back from the LONGEST case measurement. Since you have new, unfired cases measuring LONGER than your fired cases, I'd chamber your LONGEST unfired case. If the bolt closes with no resistance, you know your max chamber length is this length or longer - So I'd completely disregard your fired case measurements at this point and size your next batch of unfired brass with NO shoulder setback. Measure them after firing. If the fired length is longer than before firing, it shows two things 1) You may not have achieved your "max" brass length yet and should use the longest fired length as your new reference point. 2) It will show that all of your previously sized brass had the shoulders set back much too far each time you were sizing. When the shoulders are set back much too far - they may never blow out to full length unless the bullets are seated long enough to force the base of the brass against the bolt face. I suspect this has not yet occurred because your fired brass lengths are shorter than unfired. Tight bolt closure can also be a result of expanded bases - which I suspect is the case here. Brass does not expand to a length longer than the chamber when fired.

 

[milboltnut]

Fire Formed case backed off .001 to .002 thou... load and shoot.

what I did before is use a Hornady head and shoulders headspace guage with calipers, sizing your fire formed brass.