I'm one year into Precision Rifle shooting and I have no idea what I'm doing. I shot last year with a LR308 and swore I would build a bolt gun for 2024. The rifle is done; Tikka T3, KRG Bravo (CTR Mags) and Preferred Barrel Blanks 26" 1:75 chambered in .243 Winchester. An Arken sits on top to look through.
I broke the barrel in with 36.5gr W760 pushing 107 SMK. Slow as molasses @ 2650'/s. Lapped barrels break in fast. Next is load development.
Hornady lists the max charge of H4350 @ 37.5gr for the 105 A-MAX and 2800'/s. 37.5 grains is about 80% case fill which seems low. Of course they set the bullet at SAAMI COAL of 2.710" while I can set the COAL at 2.875 which is 0.010 off the lands and leaves a lot more space for powder.
So I did a coarse ladder test; 38.0-42.5 at .5 increment. More of a pressure test, if you will. Zero pressure signs all the way to 42.5 and all the removed primers look the same; rounded base, etc. Velocities ranged from the low of 2750 to the high of 3000'/s with the 42.5gr load. So now the questions.
Should I go faster? Out of thin air I was shooting for 2950'/s
What is a good velocity for 6mm 105 berger hybrids?
Picture is the group at 100 yards. Upper left bug hole is the 5 fastest while the lower right is the slowest. Don't know why the POI shifted. The test was to find a powder charge range and velocity only. More load development to come.
I broke the barrel in with 36.5gr W760 pushing 107 SMK. Slow as molasses @ 2650'/s. Lapped barrels break in fast. Next is load development.
Hornady lists the max charge of H4350 @ 37.5gr for the 105 A-MAX and 2800'/s. 37.5 grains is about 80% case fill which seems low. Of course they set the bullet at SAAMI COAL of 2.710" while I can set the COAL at 2.875 which is 0.010 off the lands and leaves a lot more space for powder.
So I did a coarse ladder test; 38.0-42.5 at .5 increment. More of a pressure test, if you will. Zero pressure signs all the way to 42.5 and all the removed primers look the same; rounded base, etc. Velocities ranged from the low of 2750 to the high of 3000'/s with the 42.5gr load. So now the questions.
Should I go faster? Out of thin air I was shooting for 2950'/s
What is a good velocity for 6mm 105 berger hybrids?
Picture is the group at 100 yards. Upper left bug hole is the 5 fastest while the lower right is the slowest. Don't know why the POI shifted. The test was to find a powder charge range and velocity only. More load development to come.
