Bob Crone is Vice-Captain of the U.S.A. F-Class team, and he is one of those naturally gifted shooters who has excelled at all levels of the sport. His name is on the record books at ranges all over the country. He holds the F-class 1000-yard record at Camp Butner and he has won numerous 600-yard BR and 1000-yard BR matches (Light Gun). He is one of the favorites to win the first-ever U.S. F-Class National Championship, hosted October 8-10 at Camp Butner, North Carolina.
Bob, innovative maverick that he is, shot a standard 6 BR cartridge at a number of matches against the Big 30s and took home his share of trophies. But he knew he wanted more speed when shooting 1000 yards. He put some hard thought into what he wanted in an improved 6 BR case. First, it had to be accurate. Second, it had to produce enough extra velocity to make fire-forming worth the effort. Third, he wanted it to use standard 6BR dies.
To meet all three objectives, Crone invented the 6 BRX, the thinking man's alternative to the 6 Dasher or 6 BRBS. Bob writes:
"I came up the 6BRX idea 6 years ago and had Clymer make the first reamer 5 years ago. (Clymer has specs on the 6BRX and offers the reamers.) The design is simple and basic. A stock 6BR case is fire-formed in the new chamber during match competition and you're done. The 6BRX is just a 6BR with the shoulder pushed forward .100" keeping the same shoulder angle and the same body taper. This is an increase of 11% in capacity and allows the firing of 107's Sierras at 3,033 fps, which is where they shine!
I use Redding 6BR competition 3-die sets which means that there are no custom dies to buy or wait for. Fire-form with the bullet well into the lands and maybe lose 1 case per 2 hundred. It just don't get ANY easier than this. Lapua brass, Federal primers, Varget, and Sierras. Lots of barrel life. Shoots better than the trigger puller.
I do turn my necks but see no reason not to have the chamber cut for un-turned brass as the Lapua looks so good.
Gentlemen, this is a no-brainer. It has to be one of the best, cheapest, and easiest ways to make wildcat 1000 yard rounds from the 6mm BR parent case. Just remember, you can't just push in a standard 6BR reamer deeper in the barrel! Don't even try it. You would have a pile of extra free-bore from the long neck chamber and the neck shortens on the brass by .100". And because the 6BR case profile has a slight taper from top to bottom, if you just run the standard reamer in, the base of the chamber would be WAY over-sized. A fired case wouldn't even fit in a shell-holder, much less a tight die.
With the 6 BRX the OAL on the fire-formed brass stays about the same, so you should have no problems using Redding sizing and seating dies. But if you want to make a 6 BRX, call Clymer. You need their 6 BRX reamer to make the chamber correctly. After that, load with standard dies and enjoy 3000+ fps with Sierra 107s.
I have shot the BRX extensively in F-class, and at distances from 100 yards to 1000 yards. It does the job just as well as any of the other 6 BR Improved cases, with less hassle and fewer dollars invested."