Can someone explain .308 headspace to me please?!

[Sheprador1973]

Thanks to all the above...very interesting and I didn't quite realise the depth that you can go into reloading if you so choose (in terms of headspace that is).

My needs are pretty simple really so I'll try to keep it as basic as possible. From what I can tell my Lee press cannot cam over anyway...it has stops built in i believe. Also, most seem to think that the Lee FL dies cannot bump incrementally...so if that's the case, with my current setup I cannot bump shoulders...only either FL resize or neck. Again, the general concensus seems to stick to FL sizing for stalking purposes. If I find I want to neck size and gently bump the shoulders every 3rd firing or so, I'll need a different die (perhaps a specific shoulder bump die) and/or a different press.

Please correct me if I'm missing something still. Many thanks.

 

[Sheprador1973]

I have a reloading room set up for .308, pop over if you fancy a nose.

Might well do that mate. It's been a while and you've a proven record of helping show me the way. Appreciate it thank you

 

[cjm1066]

Simplest way to visualise


Shoulder of case touches the chamber at a datum point and the bolt face is the second datum point

Case sizing (full length sizing) compressed the case to dimensions the same as or slightly smaller but within the tolerances of your chamber (if you are resizing correctly)

I always strip out firing pin when setting up my dies and work on the principle that the bolt handle should NOT drop under gravity on a re sized case but light single finger pressure only

Set your die’s incrementally to a point the bolt will close using light pressure only

Do not go past this

Do so and you are reducing the length bettween the two datum points and creating a situation where the case is not fully supported in the chamber

Hope this helps visualise the original question

Nice explanation

 

[Stalker62]

Simplest way to visualise

Shoulder of case touches the chamber at a datum point and the bolt face is the second datum point

This may help some (it helped me).

 

[Ronin]

This may help some (it helped me).

View attachment 336824

Not strictly accurate - the datum point is usually somewhere along the shoulder - not necessarily at the junction of the neck or main body of case

(For bottleneck cartridges)

For rimmed the diagram is good

 

[NP435]

Thank you guys, very helpful although will probably take a few re-reads to fully take in.

One thing that still confuses me. If I shouldn't neck size for stalking (for the well explained reasons above) and I want to keep the cases fireformed to the chamber (ie I don't FL size either) how does the case neck have the tension on the bullet upon the next reload? Or are we saying that most stalkers FL size after each firing? Apologies if I'm missing something very obvious.

Your chamber will tell you if fl size or partial fl size will work. Can you put a fired non sized case back in the chamber? If you can without pressure no need to push the shoulder at all. If not continue to screw down and size until it enters with eez or as I do some pressure on bolt closure.

 

[Utectok]

I’ve not read the whole thread but I would say it is extremely unlikely that excessive shoulder bump causing miss fires. Look elsewhere for that . Also only neck sizing is for losers lol

 

[Cyres]

It is important that you use the same case holder all the time..
D

 

[BuckhurstBen]

Get a Forster Co Ax press, quality dies not Lee and research on you tube, Eric Cortina and others of his ilk will tell you all you need to know.

 

[kenbro]

I’ve not read the whole thread but I would say it is extremely unlikely that excessive shoulder bump causing miss fires. Look elsewhere for that . Also only neck sizing is for losers lol

Why do you say that about neck sizing?
Neck sizing has its place, Imo.
Ken.

 

[Utectok]

Why do you say that about neck sizing?
Neck sizing has its place, Imo.
Ken.

Ok yes it’s fine but the body needs resizing every 4-5 reloads anyway as it usually expands and starts binding in the chamber. It also can result in difficult to chamber rounds as headspace is very tight and any small amount of detritus in the chamber can cause problems (often more of a problem when hunting). It has also been proven by cleverer people than me that there is no accuracy advantage by not full length resizing which in any case you have to do after a few firings. Neck sizing has been largely abandoned by those serious about getting the last bit of accuracy out of there setup. But do as you please!

 

[kenbro]

Ok yes it’s fine but the body needs resizing every 4-5 reloads anyway as it usually expands and starts binding in the chamber. It also can result in difficult to chamber rounds as headspace is very tight and any small amount of detritus in the chamber can cause problems (often more of a problem when hunting). It has also been proven by cleverer people than me that there is no accuracy advantage by not full length resizing which in any case you have to do after a few firings. Neck sizing has been largely abandoned by those serious about getting the last bit of accuracy out of there setup. But do as you please!

As i said previously, I cycle all my cases through the action after sizing so I know they will chamber when shooting.
Even had to try some factory rounds in a Tikka and a Bergara because they wouldn’t all fit the chamber.
I don’t like dragging the button back out through the neck with FL dies so I use a body die (On factory ammo too) when needed and do the necks separately, sometimes only sizing part of the neck.
Ken.

 

[Utectok]

As i said previously, I cycle all my cases through the action after sizing so I know they will chamber when shooting.
Even had to try some factory rounds in a Tikka and a Bergara because they wouldn’t all fit the chamber.
I don’t like dragging the button back out through the neck with FL dies so I use a body die (On factory ammo too) when needed and do the necks separately, sometimes only sizing part of the neck.
Ken.

I don’t like FL dies either because of the expander mandril! I use a body die and a lee neck collet die. One more process but it suits me.

 

[kenbro]

Ok yes it’s fine but the body needs resizing every 4-5 reloads anyway as it usually expands and starts binding in the chamber.

Bit confused here…..why would a hot case extract easily after firing but then get bigger as it cools so it’s hard to go back in?
Ken.

 

[jcampbellsmith]

As i said previously, I cycle all my cases through the action after sizing so I know they will chamber when shooting.
Even had to try some factory rounds in a Tikka and a Bergara because they wouldn’t all fit the chamber.
I don’t like dragging the button back out through the neck with FL dies so I use a body die (On factory ammo too) when needed and do the necks separately, sometimes only sizing part of the neck.
Ken.

Interesting, I've had empty cases that chambered after I finished prepping them, but wouldn't chamber after I had reloaded them.
Regards
JCS

 

[jcampbellsmith]

This may help some (it helped me).

View attachment 336824

A good reminder of the power of the Internet - to replicate mis-information. I've also got a book that replicates this dodgy image. The first diagram is incorrect. As Ronin says, there is a datum line on the shoulder that is used to define the headspace.
Regards
JCS

 

[Stalker62]

A good reminder of the power of the Internet - to replicate mis-information.

Absolutely.

I just used it to visualise that the datum point moves and @Ronin is (of course) correct.

 

[Utectok]

Bit confused here…..why would a hot case extract easily after firing but then get bigger as it cools so it’s hard to go back in?
Ken.

Sorry I might not have been clear. What I meant was if you neck size only the base of the case expands a bit and eventually (4-5 firings) starts to bind on extracting in the rifle chamber. Then it needs body sizing to easily fit. Nothing to do with hot or cold cases.

 

[kenbro]

Interesting, I've had empty cases that chambered after I finished prepping them, but wouldn't chamber after I had reloaded them.
Regards
JCS

Possibly depends on how much tolerance between neck dimensions on case and in chamber to start with?
I‘ve not experienced failure to load since I started running cases through the action prior to loading, but it wouldn’t be a big deal if it happen.
Ken.

Sorry I might not have been clear. What I meant was if you neck size only the base of the case expands a bit and eventually (4-5 firings) starts to bind on extracting in the rifle chamber. Then it needs body sizing to easily fit. Nothing to do with hot or cold cases

The base of the case expands and you resize it with a body die? Ken.

 

[Bavarianbrit]

Interesting, I've had empty cases that chambered after I finished prepping them, but wouldn't chamber after I had reloaded them.
Regards
JCS

The neck is 2-3 thou smaller in diameter after resizing so it chambers. Stick a bullet into the neck it expands out a few thou so now it is a functioning as a no go gauge perhaps.