How much case length growth measured base to shoulder should one expect with first firing?

[cdherman]

As measured with Hornady Lock N Load Headspace Guage Kit (Stoney Point)....

Yes, I headspaced my newly constructed 6.5-285 off of the new Lapua brass I have. The new brass was measuring a consistent 1.795" to 1.796" base to shoulder with the "E" bushing. Once fired is 1.800" So about 0.004" growth with firing.

I am nearly certain this is fine, about right, but I could not find any other posts that deal with it. It might be too little.

Most factory brass is pretty undersized. I have headspaced other guns off brass, one layer of scotch tape is go, two layers is no-go. And then found that, while I could fire the virgin brass OK, when I needed to resize the brass, my dies were too long. In other words my gun had a short chamber. I could not tap the shoulder back with a factory resizing die and standard shell holder. Die and shell holder made contact before the shoulder was bumping back.

I recognize that this question has a variable that none of us can know: How undersized is the Lapua brass compared to the SAAMI specs.

But I was wanting to read some more anyhow, and would like some opinions from you all.

 

[Bob Wright]

.004 doesn't sound bad. It's the belted magnums that will stretch on average about .019.
If your dies are not setting back the shoulders about .002, you can buy a set of shell holders from Redding that will accomodate your chamber. They vary in increments in .00x increments to set the brass deeper into the die. It's just for this problem. I believe there are about 10 shell holders in the set.

 

[milo-2]

IMO, .004-005" growth is perfect. and .006" is fine, get much over and a soft cup primer may be needed to get an initial firing.
In the case of your die not bumping the shoulder, I would point a finger at the die before the set headspace. The more shooting sports grow, the more we are seeing mismatched chamber-die relationships. Plus, it is easy to have some material shaved off the bottom of a die if it is still capable of constricting the base enough.
I do not shoot either anymore, but making 6 & 6.5 SLR from 243 brass was a picture perfect scenario, you controlled case growth from the first firing and I ran mine tight.

 

[sedancowboy]

Sizing dies do not take brass back to as new size but to fit in most chambers coming out of factories today. So you are correct to leave a little room to grow. The Hornady headspace gauge is only a comparater so the numbers mean nothing except to you at that moment.
To get a reference I sometimes measure a go gauge and them my fired brass to compare my chamber size to the go gauge. Most no gauges are .006 larger than a go gauge but not all.
If you don't have a go gauge then you will never know it you are within spec or not.
As long as you can resize enough to chamber a fired case then it doesn't matter what the number is.
However the problem with using a piece of brass for setting headspace is if you change brands of brass or sell the gun then you could have headspace so tight that something in the future would not fit in your chamber. That is why we have SAMMI standard go and no go gauges so everyone is on the same page. Both rifle makers and ammo and brass manufactures.

 

[sedancowboy]

[QUOTE="Bob Wright, post: 1975185, member: 10436 you can buy a set of shell holders from Redding that will accomodate your chamber. They vary in increments in .00x increments to set the brass deeper into the die. It's just for this problem. I believe there are about 10 shell holders in the set.
[/QUOTE]
Just so everyone is clear The Redding competition Shell holders do just the opposite they keep the case from going into the die as deep as a standard shell holder.
A standard shell holder is .125 height While the Redding Competition Shell holders start at .127 and go in +.002 increments up to .135 in height.
To push the case deeper into the die for more sizing you would need to remove material from the top of the standard shell holder or remove some from the bottom of the die.

 

[Mikecr]

I agree with the suggestion that the die is the problem.
You don't chamber to match dies, you make dies to match chambers.
You chamber to make what you want of your cartridge.

 

[David Emerson]

With the brass we are getting now it can be a crap shoot. I just finished a 338 rum. I used a new nosler case but ordered a go gauge from Manson. Perfect for the case. Got the go gauge and I had to chamber .015 deeper. That is a lot. At first I thought. Could Dave have stamped a no go as a go? I have a factory remington 338 rum here so I tried the gauge in it. Perfect. Just something we have to put up with I guess but .015 makes me nervous. I am going to tell the customer to buy ADG brass.

 

[SheepSeeker]

When fireforming new brass (especially belted) use the false shoulder method to limit case stretching.
Once formed I prefer the Redding neck bushing dies (after a full case prep).

 

[Bob Wright]

https://www.redding-reloading.com/online-catalog/35-competition-shellholder-sets[/URL]

Your factory die may not set the shoulder back enough for your chamber with 1 universal shell holder. Call Redding before ordering. They can explain it.

 

[jimbires]

I use these they work great . these are made to size the case less . the set includes a +.010 , +.008 , +.006 , +.004 , +.002 . . the +.010 shellholder will size the case .010 less (the case will be .010 longer ) than the standard shellholder

 

[Mikecr]

The "+" in front of each measure, i.e. +.004, +.006, is w/resp to headspace (not case depth in die).
Better description as provided by Sinclair link I posted:

The five shellholders are +.002", +.004", +.006", +.008", and +.010" thicker than normal shellholders (.125" from the bottom of the case head cut to the top of the shellholder).

That is, if you were to set a die to cam-over against any of these shellholders, then the +.010 shellholder for example, being 10thou thicker/taller at it's top surface, would reduce case entry into die by 10thou.

 

[Bob Wright]

Why not back the die out then? You wouldn't need to buy the shell holder set, right?

 

[jimbires]

Why not back the die out then? You wouldn't need to buy the shell holder set, right?

you are correct . but when I backed my die up , I didn't get consistent shoulder bump . when I use these shellholders I can cam over the press , and get just about dead nuts on shoulder bump .

 

[Bob Wright]

To the OP, what dies are you using?
Switching from RCBS (and that shell holder I tweaked by .002), to Redding dies and a standard shell holder, solved that problem and it's not camming over. Strictly adjusted. The bump is consistent and repeatable.
Annealing also improved bump accuracy as a regular brass maintenance process.