With a 125 BTip at the neck/shoulder junction, a 30BR measures approx. 2.300 in overall length. The Nosler 125 BTips I have on hand measure 1.060 long. A barrel twisted 1:14 would be slick for a hunting rig....you'd have extra rotational speed for the 125 BTips and be able to stabilize bullets in the 1.150 length range (150's, etc.) should you ever want to try something a bit heavier/longer.
I like the T3's single column magazine and the couple of T3's I've worked on have been pretty darn accurate for basically out of the box rifles.
Probably the only area you need to give serious thought to is the neck issue....when expanded to .30, there's a pronounced 'lump' at the bottom of the case neck on the 6BR brass. This is the old shoulder that's now become neck. It needs to be taken care of by neck turning. I'd caution against trying a 'no neck turn' reamer specd' off the o.d. of the 'lump' as your chamber neck diameter...this will guarantee poor results before the first case is ever fired.
Here's a link to some more info about the case:
http://www.6mmbr.com/30BR.html
Go with a standard .330 neck 'Robinett' reamer and prep the case necks per normal and you'll avoid any issues. For dies, the Redding Type S full length bushing die and a Wilson non-stainless, non-micrometer seating die is all you need for a great setup. Harrels also makes fine full length bushing dies for the 30BR...you can send a couple of fired cases to them and they'll send a die that matches best. In the case of a hunting rifle where feeding is a big concern, I'd ask for some generous sizing if going that route..or just order one of their 30BR #3 dies right from the start. Be aware that the Harrels dies don't size the full length of the neck and leave a bit of the bottom of the case neck in 'as fired' diameter. For a hunting rig, the Redding will size the entire neck length...something to consider when thinking about chambering a round in a hunting situation.
I'd suggest that a loaded round measure no more than .327 across the neck with a seated bullet. Snag a few Redding regular steel neck bushings in .324, .323 and .322 as the 30BR's love neck tension...another benefit in a hunting rig when feeding from a magazine.
Grab a pound of H4198 Extreme, one of Benchmark, some Federal standard 205's or Winchester WSR primers and you're set.
One other thing...if you're not doing the barrel work yourself, you may want to consider using a 'smith that has a
proven 'no throat' 30BR reamer. That way, he can throat the barrel for exactly where you want the base of the bullet to be in the case neck. My cipherin' shows that with the ogive profile/length of the 125BTip at the base of the neck, you're going to be close to the zero freebore range anyway. Picking the base up about .050 may be something to consider and chat with your 'smith about. If he doesn't grasp the concept and connect the dots, you need someone else to do this.
Just how I'd do it.......
