Shoulder bump

[Yondering]

Or you can measure immediately after firing to get a somewhat better idea compared to measuring cold brass........its important to have them all set back the same as uniformity is what youre after in the first place, so .002 to .004 is fine so long as they are all the same, just like trim to length and neck wall thickness......all the same.

It doesn't matter. Case to case variation is greater than any difference you'd see there. The point is to set the shoulder back as little as possible while still sizing enough so all cases chamber and extract easily. If you're using mixed brass or not annealing, setting shoulder bump to .002" average will result in some variation, probably .001"-.004" if things are working right, or a lot more variation if the brass is really inconsistent.

Setting shoulder bump is accomplished by adjusting the sizing die body down until it bumps the shoulder back the specified amount, rather than jamming it all the way down to the shellholder without measuring. With some cartridges and dies you'll end up with the die very close to or at the shellholder, but with others you'll have it backed off a bit.

[Fl0und3rz]

I always understood it to be an alternative to neck-sizing fire-formed brass intended to be used in the same rifle chamber, with 0.002" being a rule of thumb to ensure reliable chambering.  I use a Lee Collet die to neck-size, if I am looking to achieve the benefits of neck-sizing.

[Yondering]

No, it's not neck sizing. The .002" shoulder bump is full length sizing, it just involves measuring to make sure you're not bumping shoulder back more than necessary.

You may be thinking of partial sizing with a full length die, where a portion of the neck is unsized and the shoulder is not touched at all. That can work well too, but is not what we're talking about here.

[Fl0und3rz]

I think we are saying the same thing from a different angle.  Maybe not.  Wouldn't the neck be sized at least partially by the sizing die if you're hitting the shoulder?  But I guess you wouldn't get any shoulder bump with neck-sizing, if that is what you are after.

I admit I don't fire enough bolt action (still working on 50 or so fired/necked cases) or super-mega-magnums having enough case stretch to bother.  Most is either FL sized or neck-sized.

[BULLBLASTER]

Super mega magnums don’t have any more or less case stretch than any other cartridges. Case lengthening is a product of head clearance not powder burned. With small shoulder bumps or neck only sizing there shouldn’t be any or very minimal case stretch. I have some 300 win brass on its 6th during that has never been trimmed. Has only stretched .006 since its first firing.

[Yondering]

I think we are saying the same thing from a different angle.  Maybe not.  Wouldn't the neck be sized at least partially by the sizing die if you're hitting the shoulder?  But I guess you wouldn't get any shoulder bump with neck-sizing, if that is what you are after.

I admit I don't fire enough bolt action (still working on 50 or so fired/necked cases) or super-mega-magnums having enough case stretch to bother.  Most is either FL sized or neck-sized.

If the die bumps the shoulder, the neck and the rest of the case are all fully sized. It is not possible to bump the shoulder with a full length die without fully sizing the neck. The .002" shoulder bump discussed here is correct full length sizing for your chamber; in many cases running the die all the way down to the shell holder is excessive sizing but is a one-size-fits-all approach for generic sizing die instructions.

As Bullblaster said - case stretch is not just (or even mostly) the territory of bolt actions or magnums, in fact weaker actions like a 30/30 lever gun or most semi-autos benefit just as much or more. Pretty much all bottleneck cartridges benefit from correct sizing.

[jasnt]

I think we are saying the same thing from a different angle.  Maybe not.  Wouldn't the neck be sized at least partially by the sizing die if you're hitting the shoulder?  But I guess you wouldn't get any shoulder bump with neck-sizing, if that is what you are after.

I admit I don't fire enough bolt action (still working on 50 or so fired/necked cases) or super-mega-magnums having enough case stretch to bother.  Most is either FL sized or neck-sized.

If the die bumps the shoulder, the neck and the rest of the case are all fully sized. It is not possible to bump the shoulder with a full length die without fully sizing the neck. The .002" shoulder bump discussed here is correct full length sizing for your chamber; in many cases running the die all the way down to the shell holder is excessive sizing but is a one-size-fits-all approach for generic sizing die instructions.

As Bullblaster said - case stretch is not just (or even mostly) the territory of bolt actions or magnums, in fact weaker actions like a 30/30 lever gun or most semi-autos benefit just as much or more. Pretty much all bottleneck cartridges benefit from correct sizing.

: yeah: