Resizing question

[TrapperBR549]

I have been reading quite a bit on this site and very much appreciate the wisdom and help the forum provides. Thank you!
I loaded quite a bit many years ago, like in the '80's, but have been out of the metallic loading game for quite awhile. My son and I are headed west this fall if we draw so we decided we needed new guns and that we need to load our own shells.
He built a 300 PRC using a no go gauge and barrel locking nut style.
I opted for a factory Win M70 extreme weather in 300 Win Mag.
I purchased the Digital Headspace Gauge from Digital Technologies (and yes I understand it isn't actually measuring headspace) and we have made some interesting observations.
When comparing factory loaded ammo before and after firing in the 300 Win the cases grew by a consistent .015".
Is this a fairly normal number? My plan is to reload the brass bumping the shoulder back .001" and shoot again to see if it grows some more. Thoughts, ideas, concerns?

With regards to my son's 300 PRC, when comparing factory loaded ammo before and after firing, the cases actually shrank by .001". The no go gauge and the factory ammo measured the same.
Is this a normal situation? Should we still bump the shoulder back .001" when resizing?

Thanks!

 

[Rocketvapor]

No-Go??
You sure?

 

[TrapperBR549]

I am not sure, that is what he called it. I know he said he put it in the chamber, screwed the barrel on and tightened the lock nut.
What do you think it should be?

 

[Hohn]

If he used the no-go gauge to put the barrel on, the headspace is excessive. With excessive headspace, the shoulder will blow forward a lot when firing, and pull some brass out of the neck to do so.

A barrel is installed with a GO gauge, and the no-go is used to verify the bolt will NOT close on the excessive headspace value. If he actually installed the barrel with a no-go instead of a go gauge, then the rifle is dangerous to shoot and shouldn't be used until it is properly headspaced.

 

[Richard Coody]

Factory 300 WM ammo headspaces off the belt. They usually grow a lot. Will a piece of your fired brass chamber easily. If so you are not ready for a shoulder bump. Just set your die up to size the neck without bumping the shoulder and load them and.shoot them. Since this is for.hunting once your brass is fully fireformed you might.want.to bump that.shoulder 2 or even 3 thousandths. I would.cycle.every reload through the rifle before making that trip too.

The PRC it is not uncommon for brass to stretch sideways filling the chamber.and shortening the overall length on the first firing. I'm sure some on this forum are.going to go ballistic on that chamber length but.reality is if you only plan to use that brass in that rifle it really doesn't matter. You might have created a bit.of a wildcat with your headspacing but so what. Since its a barrel nut you also could easily change it. Same deal applies. If your fired and unsized brass chambers easily then it is not fully fireformed.

 

[TrapperBR549]

Thanks for the replies. I am guessing that he used a go gauge since the case actually got shorter after firing as measured from the shoulder. If there was excessive headspace wouldn't that length almost have to get longer?
I will message him regarding the gauge.

 

[BoydAllen]

Your son used the wrong gauge. He should have used a GO gauge, which is shorter.

 

[TrapperBR549]

Just heard back from him and he used a go gauge, my bad in relaying the info. That is why I bought a fully assembled rifle.

To clarify I was not measuring the overall case length, I was measuring from the base to a point about the middle of the shoulder. This distance actually reduced by .001 after firing the 300prc.
Your explanation makes sense to me Richard Coody, thanks for the reply.

The rifle shoots well. He has only fired factory ammo but after the break in procedure he shot 3-5 shot groups at 100yds that ranged from .75" to .66"

 

[Dusty Stevens]

When the body expands to fit the chamber the case gets shorter

 

[JEFFPPC]

When the body expands to fit the chamber the case gets shorter

Then when you full length resize it it grows. The brass case is amazing. Almost like it is alive.

 

[dogdude]

Jeff, Alive and Kicking

 

[Hohn]

Jeff, Alive and Kicking

..me in the nuts.

 

[K22]

On non belted cases*, if you full size and not contact the shoulder you can actually make the case longer by extruding it. If the die is set to contact or bump the shoulder back it will not 'grow" after sizing.

* I've never loaded belted cases so I'll defer to others on sizing those type of cases.

 

[Richard Coody]

On non belted cases*, if you full size and not contact the shoulder you can actually make the case longer by extruding it. If the die is set to contact or bump the shoulder back it will not 'grow" after sizing.

* I've never loaded belted cases so I'll defer to others on sizing those type of cases.

You are absolutely correct about that. Especially one that has expanded to fit a fat chamber.

I have tried a lot of different ways to ensure full fireforming before setting a shoulder bump. All kinds of measuring. I have gotten lazy in my old age and decided what works best for me is to let my chamber tell me when brass is fully fireformed. If a fired but not resized piece of brass chambers tight then i set up a very slight bump. Of course i measure it before and after sizing. Then i test that resized brass. If resized brass chambers tight i bump it a little more. Measure and try chambering. Once that shoulder bump is set i lock that die down and don't mess with it again. Many find that their shoulder bump is inconsistent or changes and they are constantly messing with the die to compensate. Not me. I find with proper annealing i have consistent shoulder bumps.

 

[Field_2_Fork]

This gives me some insight into what I'm experiencing with a set of new brass and new load development.

New Lapua brass, .243 Tikka M55 rifle. After shooting the first bunch of brass the CBTO measurement stayed the same or went down .001 on some cases. The initial charge was only 1.6 grains below Bergers max, so I assumed that would be enough to initiate the fireforming, when they shrank I was stumped!

I've been trying to figure out why, sounds like a similar situation to the OP.

Good stuff!

ETA: If I'm off base here I'd love to hear thoughts or suggestions. Thanks.

 

[Dusty Stevens]

Back when i thought i wanted to deal with a belted case (not anymore) you couldnt coordinate the belt and shoulder at all. Some factory cases i found are .025 short on the shoulder and would finally seperate on the body before the shoulder ever touched- and if it just so happened to ever touch before the case was destroyed, you couldnt bump it with the die hitting the belt way before it hit the shoulder. Even with a bunch invested in custom dies to remedy this you change brass and it doesnt work anymore.

 

[BoydAllen]

After the first firing, you ignore the belt and set the die as if it was a rimless case. The only issue is whether you get a bulge above the belt. If you need to size in that area and have a lathe, you can cut off and open up the top of a cheap FL die so that it only sizes a little more than that area. Having said that, once I went through an entire pressure test up to well past ejector marks on a custom chamber .300 WBY using one case and a one piece neck die that coordinated perfectly with the tight neck chamber and turned brass. After all of that abuse, the case chambered with no problem.

 

[K22]

You are absolutely correct about that. Especially one that has expanded to fit a fat chamber.

I have tried a lot of different ways to ensure full fireforming before setting a shoulder bump. All kinds of measuring. I have gotten lazy in my old age and decided what works best for me is to let my chamber tell me when brass is fully fireformed. If a fired but not resized piece of brass chambers tight then i set up a very slight bump. Of course i measure it before and after sizing. Then i test that resized brass. If resized brass chambers tight i bump it a little more. Measure and try chambering. Once that shoulder bump is set i lock that die down and don't mess with it again. Many find that their shoulder bump is inconsistent or changes and they are constantly messing with the die to compensate. Not me. I find with proper annealing i have consistent shoulder bumps.

Before gauges, that was the tried and true way of setting the sizing die and it still works today. If you can remove the firing pin assembly you will get a fairly accurate indication of the amount of sizing needed so the case fits the chamber properly i.e. by observing the resistance to chambering a sized case.

However now a days I measure with a caliper and bump gauge but I still spot check in the rifle chamber. It helps if you have cases all from the same lot and obviously the cases need to be dedicated to one rifle only.

I don't anneal but I suspect it does indeed provide consistency with regards to sizing. Sometimes, depending on the brand / lot of cases and the rifle I have to adjust my sizing as the cases age. I use Skip Shims to make the sizing adjustment.

German Salazar published an interesting article about the method he uses to make adjustments. He used a rubber o- ring under the lock ring and by moving it slightly clockwise or counter clockwise he could change the sizing. I never tried this method but since he is a well respected shooter I trust it works.