Neck thickness and clearance?

[Rich Coyle]

With a .300 Norma Magnum necked to 7mm what would be the neck thickness you would use? What diameter would you go with in the chamber neck?

Thanks.

 

[Mikecr]

What's your chamber neck diameter?
How thick are your necks at 7mm?

 

[Edd]

With a .300 Norma Magnum necked to 7mm what would be the neck thickness you would use? What diameter would you go with in the chamber neck?

Thanks.

If I was neck turning the brass, I would leave it as thick as I could as long as it wasn't over .015" thick. I would want the chamber neck .004" larger than a loaded round. If I was having a reamer made I would have them taper the neck so there was .004" clearance at the front and .005' clearance at the rear.

 

[Rich Coyle]

What's your chamber neck diameter?
How thick are your necks at 7mm?

That's what I'm trying to determine.

Edd,

Thanks.

 

[Rich Coyle]

Gentlemen,

I have the answer. I found the neck thickness for a .300 Norma Magnum is .017". So I am going with a reamer for my 7mm that measures .316". That will give me .002" after I turn the neck to .015". The neck length of the .300 is .290". This 7mm will be .350" so the throat lasts longer than it would with a shorter neck. At least that's what I learned from Lonny at Hornady. It will have a 40* shoulder. The reamer will be here in 16 - 20 weeks. In the mean time I save for a scope.

 

[dok7mm]

It's your build, of course, but unless you have a specific reason for running .002" overall clearance, I would be thinking at least .003" clearance. I run 4 different 7mms and use .004" in all, with very good accuracy. Different turns, depending on brass used. Just my thoughts.

 

[shortgrass]

With a .300 Norma Magnum necked to 7mm what would be the neck thickness you would use? What diameter would you go with in the chamber neck?

Thanks.

I would buy the brass I'm going to use, neck it down, seat a bullet and measure it. Then I'd take a new case or two, turn the necks after necking down, and seat a bullet to the desired length and send those examples to my tool maker for reference. .003" neck clearance is about right for a hunting rifle. Every 'run' of factory brass is not identical to the last 'run', or the next.

 

[Rich Coyle]

Thanks, guys, for your concern and input. To arrive at .002" I called two gunsmiths, two custom rifle companies, and a bullet company. They all suggested .001" - .002". So I went with the larger number. Since the reamer is 16- 20 weeks out I wanted to get it started as soon as possible.

I heard the barrel is on the way, but don't tend to believe that sort of info anymore. When it arrives then I know it's here. I have Burris Signature rings for the scope I bought until I can afford the March 5-50X56. When I can afford the scope I will have to get larger rings. I will rebarrel my consistently most accurate rifle: A Klienguenther K14 I bought in 1977. This will be its fifth barrel.