Alinwa.....
Those are some great numbers with the 6/6.5x47L that you are getting.
You know when I talk about velocities in the 243 AI, very seldom did I give a complete description of the barrel length and chamber.
First, the chambers were minimum spec with .0005 over bullet dia throat to seal all the gases behind the bullet instead of blowing around the bullet (Al, I know that I'm preaching to the choir here), ZERO freebore, with a 1 1/2* leade angle, leade angle starting right at the case mouth, .265 neck dia.
Second the barrels were 28-30" long 1-12 twists.
Third, the bullets were 70g TNT, 70g NOsler, or my 70g Customs loaded in a Rem 7/08 fire formed case, with a CCI-250, with 48.0-48.5g of Win 760. ON the 28" barrels, the velocity was usually 3800 or a touch more, and at 48.5 the vel was 3850 usually. Now, at these velocities, I have never even used my full length sizer on a case. What I found out is that when the Velocity on the 70g bullet gets over 3850, the copper fouling is increased exponentially. When I bumped the powder charge to 49.5g and changed the primer to a WLRM primer, the velocity on a 30" barrel was 4030 fps shooting a tiny bug hole. Since I was shooting p. dogs, I needed for the barrel not to copper up, so I choose the slower speeds.
Al, You and I both know that barrel length and individual barrels can have a dramatic effect on speed. Get a Bore that is oversize and your speed is much less. I always shot Hart barrels and they put the dia on the outside of the barrel so you know exactly what you are dealing with.
I tried working up a load with the Sierra 85g BTHP and at 45.5g of 760, I got bug holes with high pressure signs on the cases, and a boat load of copper in my barrel due to the increased bullet's bearing surface. I threw those cases away and shot up the 85's in a 6 Rem on yotes.
I think that a lot of these issues on speed are dealing with the yield strength on brass and the Lapua is no doubt the Mack Daddy of Hard brass. I always thought that it would be interesting to see some of the other brands of brass shot and compared with Lapua. I have been wanting to do this with the Lapua and compare it to the Rem 7/08 that I have been shooting in the 243 AI. I had some Rockwell testing of PMC, Fed, Win, And Rem cases a few years back and needless to say, the Rc of the brass is all over the map. You would think that the guy that is mixing the alloy is smok'en dope while he is mixing the batch. PMC was in a class by it's self regarding how hard it is, far better than the others!
Al, also when you have a fast twist and try to shoot light bullets, in experience you will have a slower speed compared to a twist rate that is appropriate to the size for the bullet. I found this to be true in a Custom 223 with a 1-9 twist compared to a 14 twist, in a 22 PPC with a 1-9 twist compared to a 14 twist. Also, if you are shooting the 70's in a barrel that is throated for long bullets, you are loosing a lot of pressures as the gas blows by the bullet in the throat, which is where you may be not getting the velocity numbers that I have been getting.
Al, I would in no way attack you, this has been a very good learing discussion. I would really appreciate it if you could get me a copy of the Reamer that you are using in the 6/6.5x47L.
I bring fitted necks out into the field, the varmint patch, no problems. Get the mythical "piece of grit" in there and the bugger simply will not close