Belted Magnum Headspacing

[ballistic64]

Just doing a little research for an up coming project and was wondering what the most popular method of headspacing a custom chamber for a belted magnum is? In my case it will be a 7mm Rem.
Ive been told its better to headspace off the shoulder rather than the belt,as the belt dimensions can vary considerably even within the same brand of brass.Any truth/advantage to this method?Thanks,Joe.

 

[BoydAllen]

What is the rifle being built for?

 

[ballistic64]

LR target,probably ocassional hunt.It will be close to a sendero configuration.

 

[Preacher]

It don't matter what your going to do with the rifle, it needs to headspace off the shoulder, not the belt...
Your cases will thank you for that...

 

[fdshuster]

Joe: Ditto to what Preacher said: forget the belt, pretend it's not even there, and headspace off the shoulder.

 

[BoydAllen]

Gentlemen,
When you write of headspacing off of the shoulder, do you mean when chambering the barrel, or do you mean one should pay attention to shoulder bump when setting up a FL die? The reason that I ask is that since there is no SAAMI spec. for headspace based on the the shoulder to head measuremnt of belted cases, how do you suggest that that dimension be arrived at for reamer design and chambering purposes?

 

[eddyverhoeven]

It don't matter what your going to do with the rifle, it needs to headspace off the shoulder, not the belt...
Your cases will thank you for that...

If you headspace off the belt you'll get case head separations after a very few reloads. I found this out the hard way.

Ed

 

[StevenDzupin]

When you build the rifle you head space using gages that simulate

head spacing using the Belt.

After 1st firing of new brass you use a Wilson adjustable
head space gage and set it up to the fired brass.

From then on you use this as a means to set up your resizing die
to minimize working the brass.

Hope this makes more sense. LOL

Regards,

Steve

 

[fdshuster]

ballistic64: As an 'extension' of what others have said, check out the Sinclair info posted on the 'Daily Bulletin', titled 'Setting up a Full Length Sizing Die'. It also mentions the Wilson gages in addition to the Sinclair versions. Used to load for a 300 Winchester Magnum, so I'm at least a little familiar with your questions & problems, with the belted case).

 

[Stonewall]

You can use a 7mm Rem Mag reamer headspaced tight on the belt of your brass. Then make your brass from .300 Win Winchester cases.
First set the shoulder with a f.l. .338 Win Mag die -then size in a 7mm Rem die to set the shoulder to your actual chamber size - .0015.

An old friend said on this very subject 'you don't shoot headspace gauges.'
#2 method
Jim Borden had a great article on this subject in an older Precision Shooting magazine -check the index.
He matched the reamer to the brass.

Glenn

 

[TRECustom]

Headspacing on the belt works for me. I have had good results by setting headspace to just barely close on a belted cartridge go-gage. Cartridge belt to base dimensions have been consistent enough that I have never had trouble chambering a round, and after the first firing, the case fits the chamber and could function without working the body. I have a large collection of belted brass of several calibers that are in excellent condition except for primer pockets that won't hold primers anymore. By using the belt to hold the base very close to the bolt face, the soft front part of the case stretches to fill the chamber the first time it's fired and then can be chambered with only neck sizing to hold the bullet.

I do full length size anyway, with a very, very light bump on the shoulder just to make feeding fail-safe. When I used to shoot match rifle, I always cycled all ammo through the match gun,,including alibi ammo) before a match. I used 3 different belted magnums over the years for Any-Any rifle matches and cycled at least 22 rds through those rifles before a match. I never once had a problem using tight headspacing of the bolt on the belt. No misfires and no feeding or cartridge failures. Just loose primer pockets after 2-3 firings.

My go-to hunting rifle is a .30 x .378 Wby and I have accumulated quite a few cases that are in excellent condition, except for the primer pockets.

I don't know if headspacing on the belt is the best way or not, it's just the only way I've ever done it, and it works for me. I'm apparently way out of touch, because I have always liked the belted cartridges and haven't seen any reason to switch to the large non-belted cartridges that are in vogue now.

As for accuracy, I'm only an inconsistent 1/2 minute shooter, so my rifles have to compensate for my shortcomings by being better than I am. They are.

Good question, good thread.

Thanks, Tom

 

[ballistic64]

I want to thank you guys for all the input,its what makes this site great.
Glenn,any chance of knowing the approx. date of the article Borden had in PS?
Thanks,Joe

 

[Stonewall]

Emailing Jim Borden would be quicker.
I will look for the article this week end -it's the Easter gun show tomorrow .

Glenn Jackson