Well a few weeks ago I got my barrel. It is a Krieger, 1-7.5 twist, 4 groove "conventional" rifling, finished at 30". I had it chambered in 6.5 x 284 with a "substantial" freebore to handle the new 150s. I started using H1000 and went from 54.0 to 55.5grs, however the accuracy was somewhat less than what I anticipated. Velocity was from 2950 to 3030 with ZERO pressure signs. BUT whew the accuracy was not good. I then decided to open up the freebore some more. Additionally, I spoke with my "old" riflesmith in Houston, who has extensive experience with the new Hornady 147 ELD-M and some experience with the 150 SMKs. He stated that the node is in the "lower 2900s".. Not wanting to go SUPER low with H1000 I decided to go to a faster powder. After much consideration, I settled on RL-23 and went from 47.3grs to 49.0gr to go from the Mid-2800s to the Mid-2900s. There is NO information on HOW to do that, so I extrapolated known load data from H4831sc, which is a bit slower that RL-23 but in the same ball park. Fortunately, I landed exactly where I wanted to be. The loads went from 2850 to 2960! Well Omar was correct and at 2930f.p.s. it looked promising. So today 1-31-2018, I took a load of 48.6grs out to do a ladder test of seating depths. I went from 7 thousandths INTO the lands to 24 thousandths OFF the lands. At 17 off it shot just under an inch at 300 yards in 10m.p.h. winds! SUCCESS!!! >>> Not so fast! My last 5 shot group only showed 3 shots on target. I thought "well at 300 yards, I suppose it COULD have 3 bullets in one tiny hole!" However, upon inspection, there were only 3 holes in the paper! Uh OH! I looked at the other bullet holes. Those in the 1-15 shots were clean like a paper punch. However, shots 16-25 had GRAY "lead appearing" marks just a shade below the bullet holes, which were NOT "paper punch pretty"! They were "wallowed out" in appearance! No doubt, those bullets were blowing up upon impact with the foam board backed target paper and the 2 missing had blown up PRIOR to target impact! I called up Sierra and they are now in the process of an investigation. They stated they would get back with me and had me write an email with all of the pertinent info in it. My best guess: a 1-7.5, although recommended by Sierra, is too fast for velocities well over 2900. AND the "conventional rifling" I have, instead of some 5R offering, is a bit "aggressive" for that projectile. Back to the drawing board!