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 ??
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


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 ??
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