Thread: Excessive head spacing 7mm RM - can it still be used

Reloaded about 50 rounds of 7mm RM but bumped the shoulder back 0.02" instead of 0.002" from fire form size (its PPU brass originally from highlands ammo has been fired twice)
At the time I was thinking it was too much and actually dialed it back a bit to 0.015" for most of them

Measured some Highlands & Sako Manufactured ammo and that's even further back at .021" from my fireform size.


Measured a sample of 30 rounds to get the below which is the distance the shoulder has been pushed back from the fire formed size.
Average 0.36mm 0.014"
Max 0.45mm 0.017"
Min 0.23mm 0.009"

Some has been loaded as a ladder so have a range of medium to slightly hot loads.

The question is Will it cause ruptures straight away or have I just taken a few reload cycle off the brass? (cant see that i'll ever load it more than 4 times)

@grandpamac may have some thoughts

That’s quite a big bump, potential problems are with that much it may throw shots (not group that well, only one way to find out) as excessive headspace can cause pressure issues, if you have access to a chronograph you could try a group and see if it shoots ok & the pressure isn’t excessive (High speeds, tight bolt lift, etc) if so use them and then bin the brass.

Forget using the ones loaded for a ladder test, the results could be meaningless.

Me, I’d pull the components, bin the brass and start again.

7mm Rem Mag headspaces on the belt, not the shoulder so they will be OK to use and will fire-form to the chamber.

I knew someone smarter than me would have the answer.

That's a lot but since the 300wm headspaces off of the belt, I don't know whether that's out of spec or not - you'd have to check.

No way of knowing if they're going to fail on the next firing. I doubt it. But you don't want doubt when reloading - you could pull one and inspect and feel for any thinning using a hook or paperclip. Certainly will reduce case life.

Peterson make 300wm brass that's long so that it doesn't undergo a big stretch and you can bump it 2 thou.

Originally Posted by gundoc

7mm Rem Mag headspaces on the belt, not the shoulder so they will be OK to use and will fire-form to the chamber.

This.

Although common practise now is to let the brass grow over consecutive firings until it headspaces off the shoulder, not the belt.

However, you will probably need the Larry Wills/Innovative Technologies Belted Magnum Collet die to get the area just ahead of the belt sized down (after those subsequent firings) to achieve this.

Peterson now offers 'Long' magnum brass with the explicit intention of not headspacing off the belt, but the shoulder.

https://youtu.be/XTL-Sk5dNf8

headspace is done from the belt chambering. providing you havent gone too hot or overcrimped go fire a few

Thanks All.

Im just going to fire them and see, may throw the brass on the hotter ones away if it seem to thin.

Thought:
Brass has been stretch nearly a whole 1mm over 3 firings

Manufacture Highlands ammo's shoulder is 0.53mm back from fire formed
Then for the next firing i pushed it back 0.05mm
And now I've pushed this back another 0.36mm

Totaling 0.94mm on Average which seems like a lot.

gundoc is correct The distance to the lands will not have changed as spaced off the belt and i kept the same overall length, but pressure may have been effected due to reduced space inside the case or is pressure based on the size of the brass once it has expanded into the chamber shape?


Interestingly the cases haven't lengthen that much over the two resizing from 63.25mm to 63.45mm - 0.2mm (which is still well with in SAAMI tolerances so i haven't trimmed them)
I cut one to see how thick the walls were 1.4mm - not sure if thats thin?

Originally Posted by Vandros

or is pressure based on the size of the brass once it has expanded into the chamber shape?

I would think so, as the ballistic models like Quickload and GRT use the capacity of a fired case

Originally Posted by outdoorlad

.. excessive headspace can cause pressure issues....

A sloppy case will "soak up" pressure as part of the energy produced is used to blow out the case, not just drive the bullet. You will have effectively reduced pressure.

Originally Posted by Vandros

Reloaded about 50 rounds of 7mm RM but bumped the shoulder back 0.02" instead of 0.002" from fire form size (its PPU brass originally from highlands ammo has been fired twice)
At the time I was thinking it was too much and actually dialed it back a bit to 0.015" for most of them

Measured some Highlands & Sako Manufactured ammo and that's even further back at .021" from my fireform size.


Measured a sample of 30 rounds to get the below which is the distance the shoulder has been pushed back from the fire formed size.
Average 0.36mm 0.014"
Max 0.45mm 0.017"
Min 0.23mm 0.009"

Some has been loaded as a ladder so have a range of medium to slightly hot loads.

The question is Will it cause ruptures straight away or have I just taken a few reload cycle off the brass? (cant see that i'll ever load it more than 4 times)

Greetings Vandros,
The problem you are having is well known. Chambers cut for belted cases have often been generous to say the least. As caberslash has mentioned current practice for many is to size the case just enough to set the shoulder back enough to chamber easily. This is done to prevent head separations as early as the third firing if the case is sized all the way back to the belt. This often allows another problem to develop in that the case in the unsized area just ahead of the belt expands an makes the case chamber hard or not at all in some rifles. There is a die available to correct this as caberslash mentions below but a low cost option for the 7mm Rem Mag would be to use a stripped .300 Win Mag FL die body to size that area (take the decapping assembly out first). This may not fully address the tight chambering so a fix I recommended for a friend with .308 Norma Mag cases that would not chamber was to sit the case on top of the shell holder and carefully run it into the die far enough to fix the problem. Next knock the case out with a rod like the one that comes in the Lee Loader kits. It worked a treat for my friend. Only use these steps if you have a chambering problem and only enough to correct it.
As far as pressure goes any change in case volume is miniscule and unlikely to have any measurable efect on pressure or velocity.
To check for thinning of the brass you are looking for a thinning ring inside the case. You can feel for this with a bent bit of thin wire with a sharp point just up from the case head. Easy to detect once you get the hang of it. If you want to section a case to check you need to do it lengthwise and dress it up with a file so you can see things clearly.
Regard Grandpamac.

My mates 7mmRM can stretch new fired cases out .06" in single firing. So FLS is not really an option.

Greetings Again Vandros,
I just realised that I did not specifically address your question of will the excess headspace cause ruptures. Unfortunately the answer is I don't know. You could carefully inspect the outside of the case about 6mm up from the base to see if there is a bright line part or all the way round the case if so these should not be fired. The other way is to pull the projectiles and save the components followed by checking with the bent wire as above. I see you live in Auckland so see if you can find an older handloader to help you with this. A whole bucket full of posts is nowhere as useful as 10 minutes of one to one instruction.
One of the options for setting headspace accurately is the Redding Competition Shell Holder kits. From your measurements these may not have the adjustment range needed (at + .010 inches) in your case. I ran into this problem recently with my 6.5x55 rifles. Two sets of dies including some new Redding dies both set back the shoulder excessively. My t3 has a tight chamber with fired Lapua cases barely longer to the shoulder after firing than new. Even the + 0.10 shellholder sets the shoulder back a little more than I would like for this rifle and way too much for my M38 and a friends M77. It seems that the US diemakers are working to a shorter headspace dimension than the Scandinavians who invented the round in the first place. Unfortunately this type of arrogance is far from rare in the US.
Regards Grandpamac.