Headspacing 7 MM Remington Magnum

[gilream]

I need some opinions from the experts on this topic please. I shoot a custom 7MM Remington Magnum. I have measured the headspace on several fired cases using maximum loads with the Stoney Point headspace gauge (that attaches to the caliper). All brass is Norma and from a single lot and I have measured 10 cases each of virgin, once fired, twice fired, and 6 cases fired three times. The cases have never been touched with a FL resizing die, only a Redding Bushing Neck die. I recently purchased a Redding Type S FL Bushing die and intend to FL size from now on. From the measurements below I’d like to know:

What is my chamber’s headspace? and

Where should I bump the shoulder to going forward?

Virgin brass: 2.101
Once Fired: 2.1156
Twice Fired: 2.1183
Three Firings: 2.1202

I have not removed the firing pin from the bolt, but I can feel a slight resistance to closing the bolt with some of the twice fired cases and the three times fired cases. The once fired brass gives no ‘feel’ when I close the bolt on it at all. I’m guessing that my chamber headspace is about 2.117 and I need to set the shoulders back to 2.115 or 2.116

This is a very elementary question I know, but I plan to start annealing cases and using the above mentioned die for more consistency and I want to make sure. Thanks for any comments.
Mike

 

[Fuzzball]

Re: Headspacing 7 MM Remington Magnum

What your headspace (chamber) is irrelivant for reloading. Just set your case shoulders back to where they are after the first firing and all will be well.

 

[TresMon]

Re: Headspacing 7 MM Remington Magnum


If your wanting ultimate accuracy from a belted mag have your 'Smith move the belt relief in your chamber forward about .015 to give it some breathing room.

A belted mag was originally intended to headspace off the belt. Of course for greater accuracy you want it to headspace off the shoulder of the case like any other rifle round.

Depending on your chamber dimensions (factory loose "sporter" of custom match) you may be able to get her to headspace off the shoulder with no additional chamber work.

I respectfully disagree with Mr.Fuzzb. If your looking for ultimate accuracy you need to be bumping your shoulder back .002- .003" MAX from the true shoulder length in your chamber.

From what you gave in specs I'd be bumping it back to 2.118" or two thou off your longest measured cases.

Best wishes and keep at it.

 

[bigwheeler]

Re: Headspacing 7 MM Remington Magnum

Belted mags headspace off the belt with new brass, after that the shoulder. Treat it
like you would any other round. 001 to 002 under chamber length is fine. I have
never used gauges, just my bolt and chamber. May get some someday though,
they work.