Re: 6.5mm 123gr Scenars?
Just started working up some loads yesterday in my 6.5x47L. 25" Krieger 8 twist on a Surgeon action w/ bushed firing pin.
Background: My first loads for this rifle were with 130gr Berger VLD's. They are damn accurate with 37.5gr Varget, CCI 450 primers .010 into the lands. But I haven't been able get up into the 2900 fps range -2825fps is what I got - which is fine considering the accuracy. I shot this load out to 1250 on steel two weeks ago and it was dead on for my JBM Chart. Although I need more practice beyond 900yds, and a target a little larger than 8-9" because the wind tunnels to the target where I shoot. This load is not a slouch and if I ever decide to hunt with this rifle these are the bullets I'd choose.
After this load I ran some charts on the 123 Scenar, and saw no real BC benefit to the 130+grainers for long distance if I could get the speed up on the 123's. JBM showed less drop and drift.
Yesterday I loaded up some test rounds starting at 37.7gr Varget, up to 38.6 - perfect load test day at 104* with heat index of 108 and 38% hum, if I'm going to see pressure signs both physical and chrony it will show in these temps. I loaded up 5 rounds of each, with two different bullet seating options - .002 into the lands and .002 off. 38.3gr Varget got me to 3015fps seated into the lands .002 with new brass, neck tension of .288. This is the speed which is near the edge of where I've read many folks started to lose accuracy actually anything above about 3020. Most reported high accuracy nodes that I've read and heard from other shooters tend to be between 2900 and below 3020. I still need to dial in the load somewhere between 38.1 - 38.4gr, CCI 450 primers. <span style="font-weight: bold"> NOTE: START LOWER THAN THIS it's safe in my rifle and chamber but may not be in yours.</span> Start somewhere around 37.5 or 37.7 if using Varget.
H4350 is another good powder but speeds are lower IME and will take 40-41.5gr to accomplish the same thing Varget will accomplish. Other good powders are RL17 and RL15 - although I don't like temp sensitivity so I avoid RL powders.
Hope this helped somewhat. You've got a little more case capacity to work with, so speeds will be up there a bit more for .260. Also 4350 will probably be the best powder choice for you unless running 140-142's then 4831SC might be the better option.