7mm RM case neck thickness - help please!

[Timber338]

I'm wondering if some experienced 7mm RM reloaders can provide some help. I have a friend that I am helping to get set up with new Redding dies, including a FL resizing bushing die. I want to get him set up with the correct range of bushings so that he can properly size his necks to -.003 interference for his hunting rig.

First, is there a general recommendation for what is the best 7mm Rem Mag brass? Or a top 2 or 3 choices?

Second, is there an average neck thickness that seems to be consistent with this brass? My 300 win mag brass typically comes in right at .014 neck wall thickness with the brass I use, but no idea where this average thickness might be for the 7mm.

I doubt that the average neck wall thickness is going to be thicker than .014 for the 7mm, and a bit of a hunch that .014 is thicker than most 7mm neck walls. So right now my starting point is to assume the average neck wall thickness is .0125, and get bushings around that size.

So right now, I'm thinking the following bushings:

.304 (will give .003" interference with case neck walls at .011")
.305
.306 (assuming this is nominal .0125 thickness - a complete guess)
.307
.308 (will give .003" interference with case neck walls at .0135")

What do you guys think of this? Thanks for your help!

 

[MudRunner2005]

To get the proper measurement, pick your brand of NEW brass. Load your bullet of choice into it. Take your calipers and measure your case neck's width, with the your bullet of choice loaded in the brass as if it were a loaded round.

Then take that number, and subtract .003" and whatever that comes out to, is what size bushing you need.