necking down to 7mm

[Geezerbiker]

I remember reading somewhere a long time ago that the 7mm08 was designed so the home reloader could size .308 Win brass down without needing to ream. Checking length and trimming if needed was recommended...

Anybody else recall that?

Tony

 

[stagpanther]

For lack of better description--it's sometimes a "push comes to shove" thing as to where the displaced brass goes when compressed. Since NH shooter mentioned he was having problems with the shoulder--my guess is that he's encountering too much friction between the expander and the inside of neck while attempting it in one operation.

 

[Marco Califo]

Buying new quality brass like Starline 7mm-08 takes the trouble-shooting, frustration, and guessing out of the process. Starline brass also has the correct headstamp
To differentiate it from 308/7.62 brass.
Starline 7mm-08 brass costs about the same as their 308.
No backorder right now.
https://www.starlinebrass.com/7mm-08-remington

 

[Reloadron]

While I agree that just buying 7mm-08 Remington brass is obviously the most practical and best way to go sometimes getting the brass you want is easier said than done. When I resized .308 Win to 7mm-08 Remington there was no 7mm-08 Remington brass to be had nor even 7mm-08 Remington loaded ammunition to be had. I did have a mountain of 7.62 NATO brass so that is what I used. On another note as UncleNick points out, doing the math my case neck thickness increased by 0.001" going from 0.014" to 0.015" which is nothing to be concerned about or requiring ID neck turning. Measured using a Starret case neck micrometer. So while just buying 7mm-08 brass is the ideal solution the answer to can .308 Win (7.62 NATO) brass be run through a 7mm-08 die and be used the answer is yes keeping in mind the head stamp and never confuse your brass which is a very good point.

Ron

 

[Unclenick]

As Geezerbiker mentioned, the 7mm-08 Rem is designed to be formed from 308 Win brass without touching the neck or having to trim the finished case length. This avoids forming a "dreaded donut," as would happen when starting with brass that had a taller shoulder. This is confirmed when you look at the SAAMI drawing dimensions from the case head to the start of the shoulder, which is the same for both cartridges as is the shoulder angle and all diameters up to that point.

What that all tells you is that if there is a shoulder problem, you could try resizing first in a 308 die. That will set the base-to-shoulder length. After doing that, the 7mm-08 die is just bringing the neck diameter down and forming the last few hundredths of the shoulder from the bottom end of the 308 Win neck, which should be pretty easy going. The rest of the shoulder should then go untouched. If doing this is causing a problem, I would check for an existing internal donut in case the brass manufacturer screwed up somehow.