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

[cw308]

I full length size only for my benchest 308 . How I measured my chamber length was the order a Go Gauge , using a stripped bolt I built up the base of the gauge untill I felt the bolt close with very little resistance . Recorded that measurement with the RCBS Precision Mic , Then using the Redding Competition Shellholder Set of 5 , using the lowest deck height shell holder ,set your die to full contact , changing deck hights until you get your .002 less from your zero measurement on the mic. Should be or is more accurate with a stripped bolt. You can find on line the stripped bolt method to find head to datum and head to ogive measurement. The three best tools I found that worked for me is the RCBS Precision Mic , Redding Competition Shellholder & the Redding Competition Seating Die . Hope I Helped in some way.
Chris

 

[K22]

Will try not to repeat what's already been said. This is a fairly simple process and concept so don't make it more complicated than necessary.

Comment of Sizing:
Full sizing also sizes the body of the case radially aiding in chamber fit. Since I'm primarily a hunter I strongly believe in full sizing every time. After many years of reloading using various methods, i.e. neck sizing, partial sizing, and full sizing I can attest that full sizing, done properly, does not reduce case life or degrade accuracy and produces reliable functioning reloads which is critical to a hunter.

Comments of Procedures:
While I use a bump gauge and caliper to set my FL die, the ultimate gauge is your rifle chamber. What you are trying to achieve is bolt closure with only very slight resistance of the case being chambered. The best way to gauge this is to remove the firing pin assembly so you can get a more exact feel of bolt resistance to chambering a sized case. Before gauges, the manual method was used quite successful to set up FL dies to obtain the optimum fit for that rifle chamber rather than just screwing the die down per the die mfg's instructions which often resulted in over sizing . I prefer to measure set back but the manual method still works.

The .001 to .002" shoulder set back measurement is the standard for bolt rifles. You simply measure the fired case with primer removed and set your FL die to push the shoulder back the desired amount. Check the sized case in your rifle chamber to verify that the case chambers with minimum resistance.

All this assumes you are using the same cases in the same rifle and rotating their use so that cases received uniform number of firings.

You don't need a lot of fancy equipment to measure set back. You just need a bump gauge and caliper. I like the Whidden gauges since they are caliber specific, inexpensive and simple to use with no inserts thus no interfaces. If you're reloading you should already have a suitable caliper.

As cases age or if you change brands you may have to adjust your FL die to obtain the desire set back. I like to check three cases every 2 reloads to make sure the die setting is still appropriate.

You don't special shell holders either which can be quite expensive.* They can be useful if you are loading for multiple rifles of the same caliber but even then you do need them. There are other effective and much cheaper methods for adjusting FL die for multiple rifles of the same caliper but I won't go into that here. If you are loading for a single rifle / caliber then all you need to do is adjust the FL die by tuning the die in small increments until you reach the set back you want.

*if you go this route make sure you check the dimensions. I had a friend who had two of them that were off about .002" from the marking inscribed on them.

Bottom Line: you want to size your cases to provide the optimum fit for your rifle chamber so that your reloads will chamber and extract flawlessly without over sizing the case.

 

[JimSC]

everything you always wanted to know about headspace but was afraid to ask

Amazon.com

 

[Richard Coody]

It is an incremental learning.process that gets simpler as you grow more experienced. One thing you will learn along the way is SAAMI and case gauges mean nothing to the precision reloader. Your case gauge is your rifles chamber.

Step one learn what fully fireformed cases feel like.
Step two learn how to measure base to shoulder datum
Step three learn how to set up your sizing die for bumping the shoulder

All reloading dies are not the same. Always try chambering a piece of your sized brass. If it doesn't chamber easily you need find out why before going any further.

Only way to learn these things is by doing it. You will make mistakes but that is how you learn. An experienced mentor can shorten the learning curve. Utube is your friend. Lots of good and bad information out there in internet land. Telling the difference can be difficult for the beginner. Just remember reloading is a simple process. That is until you go down the rabbit hole.

 

[Bill K]

You are making it too complicated and chasing your tail. Take a fired case, from your rifle and use it to set your FL die to just touch the case as you run it into your die, have just a very slight resistance and then close that in your chamber, you want just a slight resistance there also. If you have that, set your FL did at that point and leave it there.
They just resize, load and fire your cases as normal and use them in just that rifle.
K.I.S.S. and you will be happy.

 

[milboltnut]

Hornady made a note with their Head and Shoulders headspace gauge kit that most reloaders bump back the shoulder .001 to .002 thousands. That's plenty to prevent hard extracting and provide enough headspace to function.

 

[gambleone]

Where's Guffey?

 

[Richard Coody]

Where's Guffy?

He was kind of entertaining. His riddles required thought.

Impossible to bump the shoulder back!

Actually what he said was true. You actually don't just move the shoulder back. You form a new shoulder each time you resize a fired case. A tiny piece of shoulder becomes neck and a tiny piece of case body becomes shoulder. The reverse happens upon firing.

 

[JFrank]

Also the case doesn't space.

 

[milboltnut]

He was kind of entertaining. His riddles required thought.

Impossible to bump the shoulder back!

Actually what he said was true. You actually don't just move the shoulder back. You form a new shoulder each time you resize a fired case. A tiny piece of shoulder becomes neck and a tiny piece of case body becomes shoulder. The reverse happens upon firing.

splittin hairs ain't ya?

 

[Richard Coody]

splittin hairs ain't ya?

Oh yeah

No doubt!

Have you ever read any of Guffey post?

I bump shoulders regularly.

 

[JFrank]

Oh yeah

No doubt!

Have you ever read any of Guffey post?

I bump shoulders regularly.

You do realize that's impossible using a die with full body support.

 

[wkdickinson]

Several people have referenced setting headspace by feeling a slight resistance as you close the bolt. In order to do that they've mentioned the need to remove the firing pin, to get the "feel". But you also need to remove the extractor and ejector in order to truly feel it.

None of this is going to work very well unless you anneal, there is just too much "springback" in unannealed cases.

 

[Richard Coody]

Several people have referenced setting headspace by feeling a slight resistance as you close the bolt. In order to do that they've mentioned the need to remove the firing pin, to get the "feel". But you also need to remove the extractor and ejector in order to truly feel it.

None of this is going to work very well unless you anneal, there is just too much "springback" in unannealed cases.

Actually I believe you may be misunderstanding what they mean. Stripping the bolt is probably the best way but once you know the feel I find it not necessary.

I want the bolt to close tight with resistance on a fired piece of brass. That way I know the brass is fully fireformed

I will then take that case and measure base to shoulder datum. Want sized brass 1 to 2 thousandths shorter.

Take that case and put it in the shell holder. Carefully in tiny increments adjust the sizing die till you get that 1 to 2 thousandths bump. In time you will learn the feel when the die hits the shoulder.

Now chamber that sized piece of brass in your rifle. If it chambers easily put a lock ring on that die and don't mess with it any more. If not you have work to do.

 

[cw308]

Using the competition Shellholders you have full contact , die to Shellholders , tried bushing dies and run-out was more , full length standard die was much better .001 No shortcuts in case prep.

 

[milboltnut]

Actually I believe you may be misunderstanding what they mean. Stripping the bolt is probably the best way but once you know the feel I find it not necessary.

I want the bolt to close tight with resistance on a fired piece of brass. That way I know the brass is fully fireformed

I will then take that case and measure base to shoulder datum. Want sized brass 1 to 2 thousandths shorter.

Take that case and put it in the shell holder. Carefully in tiny increments adjust the sizing die till you get that 1 to 2 thousandths bump. In time you will learn the feel when the die hits the shoulder.

Now chamber that sized piece of brass in your rifle. If it chambers easily put a lock ring on that die and don't mess with it any more. If not you have work to do.

Get a Hornady Head and Shoulder HS gauge, when bumping the shoulder back.

 

[STS]

As suggested above, take a fired case that has some resistance to bolt closure and set your die so that it closes with the slightest feel of contact on the case head as the bolt handle stops the bolt rotation. That Hornady gauge has two purposes, to increase Hornadys revenues and to confuse new reloaders. It's wildly successful at both. You don't need that gauge to figure out where to set your sizing die.

 

[wagonman]

Where's Guffy?

He pops up with his riddles on calguns.net, when the words bumping shoulders comes up most guys are just baiting for his response

 

[milboltnut]

As suggested above, take a fired case that has some resistance to bolt closure and set your die so that it closes with the slightest feel of contact on the case head as the bolt handle stops the bolt rotation. That Hornady gauge has two purposes, to increase Hornadys revenues and to confuse new reloaders. It's wildly successful at both. You don't need that gauge to figure out where to set your sizing die.

where did you buy your crystal ball from ? You have no idea where the case is headpace wise just "adjusting" your die.

 

[Webster]

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 ??

I reloaded good ammo for almost 45 years before I heard the term HS or bump related to sizing brass.