Dan B, .245 loaded neck dia. with .248 neck chamber will give you .0015 clearance per side,which is considered a match grade neck clearance.
Just out of curiousity,whats the thickness of your brass.Or what im asking is how much your turning off to get to .245?
The Constitution shall never be construed to prevent the people of the United States who are peaceable citizens from keeping their own arms -Samuel Adams
107gr SMK's seated 20 thou off the lands over 29.5gr Varget in a Lapua case lit off by a CCI450 works pretty slick in my Savage 10FP w/ a 27" SSS/Douglass barrel w/ a 1-8" twist @ 2700fps. The barrel came as a .272" neck no-turn chamber, but I did turn anyways, just a light cleanup (50-80%) to about 0.0131"... loaded rounds measure just a RCH over .270" at the neck and shoot very, very well out to 500yds (furthest I've shot it so far).
I haven't tried RE-15 yet, though I think I also read some interesting results in one of the gun-of-the-week articles (36? or so) using IMR4895.
I've not turned any yet. The brass is Herter's and I've heard the necks are thin to start. I bought the gun as built and the seller can not find the dies...so he's buying me a new set...so I'm waiting on the dies to size all the parent .222 RM brass then turn, load and ff.
Did some digging in my notes when I was playing with a 6BR. I used Rem brass (7BR brass to be exact) and had no problems at all for LR plinking and such. Clays at 750yds were a no brainer.
I started with some 70gr TNT but these proved irratic in QC from lot to lot. Just fine for PD popping but certainly not a LR match quality bullet.
I used CCI BR4 primers, H322, Rem brass with 2 thou chamber clearance and a 12 thou neck thickness. Was getting 3300fps with these TNT's molied.
I then started LR shooting and found one of the best kept secrets, the 87gr Vmax. These things are accurate and fly superbly. Just adjusted the load amounts and was shooting 1's and clays at said 750yds. Velocity was 3150fps.
Things to watch out for: Do turn again once necked down and fireformed to 6mm. You want to keep those necks as consistent as possible. I just do a light cut and remove up to 75% of circumferance. Don't like under 12thou or over 14thou neck wall thickness.
Anneal your brass. Because of the tight tolerance, you don't need to size the necks. The spring back is enough to hold your bullets again. I just popped out the primers and seated a bullet. This worked great for a while then loads went very irratic. The cause was work hardening of the necks.
Remember that in a BR chamber, that brass is going to be reloaded over 20 times. I would suggest annealing at least every 6 times, more often if you compete.
A bushing or collet neck die is the way to go. I found that 2 thou of neck tension was min with up to 4thou being ok.
As I work through the cannon phase, I am looking back at such nice cartridges as the 6BR. No muss, great accuracy, no recoil/noise, low cost, etc. Maybe a barrel will be cut in the not too distant future.
I hope that you will enjoy the 6BR as much as I did. Just keep an eye on your groups. If you get a flyer, mark that brass and if it throws the shot the next time, get rid of it.
I have done this sorting on all my target rifles. This way I get components that are as close to identical as possible. I find this much more productive then any other type of brass sorting.
Anytime I can shoot in the 1's and 2's at moderate ranges with a LR rig, I am happy.
Thanks for the excellent info. I noticed that the resized necks (7mm to 6mm) had "ripples" and figured I should turn them again but was reluctant to mess with things too much in the learning phase... I'll trim them again as you suggest/state.