Exactly what is the difference between the 30BR and the 308 Inch and a Half

[picketpin]

Thinking about building a Ruger #1 in 30BR for 100 yard shoots. My gunsmith has a 308 inch and a half reamer, Shilen who I would probably get the barrel from has a 1:17 30 cal barrel and a 30BR (Robinet 30*) reamer. The place I rent reamers from time to time show 308 Inch and a half and 30BR. I just want whatever is "standard" What am I asking/looking for.?

 

[tonedaddy]

30br has a steeper shoulder angle.

 

[gunsandgunsmithing]

Also, in typical brass, the primer and flash hole sizes are different.

 

[Tim Singleton]

The "industry standard" it what has become a "Robinett Reamer. Basically, it features a .330 neck, a max case length of 1.510, and a "zero freebore" going into a 1.5 degree lead..

http://forum.accurateshooter.com/index.php?action=dlattach;topic=3778611.0;attach=881305

 

[Outrider27]

Also, in typical brass, the primer and flash hole sizes are different.

More or less agree, but the BR family of cartridges was loosely based on the .308 x 1 1/2 cartridge and no one made brass for either the .308 x 1 1/2 or what became the BR family of cartridges in those days, so primer and flash hole size was basically determined by whether you used regular .308 Win brass or the Remington .308 BR brass. Either way, the first die sure moves the shoulder back a bunch, but if you use the .308 BR brass you ended up with a small rifle primer. In short range benchrest this may have made a difference; in IHMSA metallic silhouette, where the 7mm BR was common, I never detected a difference large enough to matter, even at 200 meters, regardless of which primer the parent brass required, though most of mine used the small primer .308 BR parent case - the large rifle primer cases were just a 50 case experiment. Now that you don't have to roll your own, small primer pockets do rule for the BR cartridges, but if you're shooting a .308 x 1 1/2, I expect you still have both sizes show up.