some dimensions;
The chamber in this 6.5BRM barrel is 2.030"
case length; 2.015" (trimmed)
base dia, .415"
shoulder dia, .405"
bottom of base to shoulder, 1.650"
bottom of base to shoulder/neck junction, 1.776"
neck dia, .293"
Rim thickness(WW case).055"
These are taken from a trimmed and neckturned case, fired, before sizing. I turn all necks to .012" wall thickness.
Browns chamber in this barrel is very tight. One batch of 30-30 brass I acquired at a gun show(once fired R-P) wouldn't chamber with a loaded round. until I turned the neck. Since then I turn all the necks and accuracy has been a lot more repeatable.
The base of the neck is a radius rather than an abrupt transition. Neck length is approximately .240-.245. I you use the dimensions on Browns web site the neck length figures to .270" I wish it was that length! Almost like a Weatherby round.
37.gr of H4350 will fill to the base of the neck.
It would be almost impossible to overload this round with H4350 or 4831 and a 140 gr bullet
You could underload it with those powders.!!
I use a lot of 30-30 cases for several other cartridges and the uniformity varies by lot. Sometimes a LOT. Hornady and the last batch of WW were very consistant.
I can't reccommend the Barnes TSX bullets in this round. the velocities are not high enough to get reliable expansion. I am going to load some Northfork bullets I have for another 6.5 rifle(6.5x53R- 256 Mannlicher- an English Double) They should expand reliably. How they will shoot? I am a big fan of Northfork bullets they have a wide usable velocity range.
http://www.northforkbullets.com/magento/bullets/
This has been a fun cartridge to play with and am looking forward to hunting this year with it. The accuracy from the start has been exceptional. If you like tinkering with wildcats this is an easy to load round. The Brown people are great to do business with. Browns dies are a combination of Lee FL size die and Hornady seating die. I was always a bit sceptical of Lee dies until I bought a set a few years ago.
Hope this helps.