Into lands or false shoulder to fire form belted brass

[cape cove]

Just because your shoulder has moved forward on the initial firing does not mean that your case has stretched. Measure your case oal before firing and after, not the shoulder. The belt holds the case in place and the shoulder is blown forward, but oal basically remains the same. The neck may be a little shorter. JMO

 

[gohring3006]

You won't normally get a full case stretch on the first firing. I usually wait till at least the third firing to set up my shoulder set back.

 

[Gwine]

It sounds like the consensus is to not worry about it and just load and shoot. Sounds like a you guys saved me some time.
This is why I asked, having never loaded new belted brass I didn't want to miss anything.
Thanks again for the input.

 

[Gwine]

I will definitely measure before and after firings and note it. I may put a shoulder on one and compare just for my curiosity.

 

[25WSM]

Dean is right for absolute sure on the lube. A light oil is only needed when doing the mild load fire forming method.
Shep

 

[Quarter Round]

7mm rem mag headspace
https://www.longrangehunting.com/threads/7mm-rem-mag-headspace.85163/

Below shows the variations in belt thickness and headspace, and if I remember correctly someone here stated that the average belted rifle has about .004 head clearance. And this can vary on the cases belt plus and minus manufacturing tolerances.

And as a side note, I have had new .243 Winchester cases as much as .009 shorter than chamber headspace.

Below are .308 cases fired in a brand new Savage rifle and full length resized until they failed. Look at the bottom chart and note that these cases did not start to stretch until after the 6th firing.

Along with all the measuring, I like to use a piece of wire and feel inside the case. I've found with this method the point of separation can be felt even on the first firing. The brass must flow somewhere. This method is not meant to replace sound practices of measuring for problems though, but just another tool.

 

[25WSM]

The ribs concentricity guage has the best little case probe out there. If there is a shadow I bet it can feel it. But you are right any paperclip with a hook at end will do. Yes we want all the stretch to be at the shoulder area not the web.
Shep

 

[nicholasjohn]

I will definitely measure before and after firings and note it. I may put a shoulder on one and compare just for my curiosity.

That, Sir, sounds like a good idea. You might not learn the answer to the question you started out with, but I'll bet you will learn something.

 

[Gwine]

In case anyone was curious.
I put a shoulder on 2 of my brass (expanded to 30cal then back to .284 using the stripped bolt to feel a slight crush fit on close)
Loaded 4 (2 with shoulder 2 without) with 168 Berger, 65g 7828.
The 2 with shoulder shot 2828, 2822. 3/4" apart horizontal.
The 2 Without shot 2769, 2761. Touching horizontal. (Magnetospeed)
The 2 cases with shrunk .008" and .006". (Maybe due to the crush fit?)
The 2 without did not change length.
All 4 grew .014"at the shoulder. .004" shy of my old cases.
Not sure why the shouldered ones were ~60fps faster, maybe the shorter gripping surface on the neck? They did seal differently in the chamber. Left 2 had shoulder.

 

[nicholasjohn]

In case anyone was curious.
I put a shoulder on 2 of my brass (expanded to 30cal then back to .284 using the stripped bolt to feel a slight crush fit on close)
Loaded 4 (2 with shoulder 2 without) with 168 Berger, 65g 7828.
The 2 with shoulder shot 2828, 2822. 3/4" apart horizontal.
The 2 Without shot 2769, 2761. Touching horizontal. (Magnetospeed)
The 2 cases with shrunk .008" and .006". (Maybe due to the crush fit?)
The 2 without did not change length.
All 4 grew .014"at the shoulder. .004" shy of my old cases.
Not sure why the shouldered ones were ~60fps faster, maybe the shorter gripping surface on the neck? They did seal differently in the chamber. Left 2 had shoulder.View attachment 163019

I did this years ago with 30-06's, to fire-form them into 30-06 Ackley Improved. Cases that were loaded with the bullets jammed into the lands showed less shrink in overall length than the ones on which I had made the secondary shoulder ( by necking up to 8mm, then back down to 30 caliber.) I think this is probably due to the stretching of the brass occurring differently with the two methods. When the secondary shoulder is employed, the cartridge cases are stretching sideways ( relative to the direction of the bore ) and circumferentially, and the brass has to flow in from somewhere to fill out the angles of the shoulder of the chamber. It came from the neck & shoulders moving aft to fill in the voids, and the cases ended up shorter in overall length.

With the other method, there is also longitudinal stretching occurring, and the brass that fills in the shoulders all came from the walls of the brass right above the web. This is because the case is driven forward by the firing pin impact, where it grips the chamber walls as it expands sideways, and then the case head is driven backward against the bolt face. This stretches the walls of the case, and the material all comes from the area just ahead of the web.

This is also why a lot of guys recommend lubricating the cartridge cases with WD-40 prior to fire-forming. This is said to keep the case from gripping the walls of the chamber, and negates the likelihood of all the stretching taking place at the pressure ring just ahead of the case web. It does it with increased bolt thrust, though, so even loads with moderate pressure may show high pressure signs on the case heads and primers. That is one reason why guys like the secondary shoulder method.

I think that you may be seeing the same thing with your 7mm magnum, but to a slightly lesser degree than what I was getting. It was pretty pronounced in my case, because the Ackley Improved chamber was a lot bigger than factory 30-06 brass than your 7mm brass is relative to your chamber. The principal, though, is pretty much the same. The whole idea in employing the secondary shoulder in your case is to keep from stretching your cases thin at the point on the case walls that is just ahead of the web. This is where they tend to separate after several firings and re-loadings. The idea is to reduce this stretching as much as possible, but it cannot be completely eliminated.

 

[Rich Coyle]

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[jlreff]

It is a real issue. New brass has the shoulder pushed too far down. If you don't put a false shoulder you'll get too much case stretch in front of the belt. If the brass was fired brass then I throw it out after five firings to avoid case head separating.

 

[Rich Coyle]

It is a real issue. New brass has the shoulder pushed too far down. If you don't put a false shoulder you'll get too much case stretch in front of the belt. If the brass was fired brass then I throw it out after five firings to avoid case head separating.

Instead of automatically throwing them away you could make a pointed wire tool to reach into the case and check if there is even a beginning separation.