Re: Load development question
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Deadshot2</div><div class="ubbcode-body">There's so much freebore in my rifle I just work on powder charges. When I tried to reach out closer to the lands I barely had any bullet in the neck.
Funny thing though, 43.5 grains of Varget behind a 175 gr custom comp nosler seated to magazine length (2.800) in my .308 shoots nice tight groups. Bug Holes at 100 yards and quarter sized groups at 300 yards.
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Fine tuning a load with seating depth, especially if you are following the OCW principles, has nothing at all to do with a relationship with the lands...and everything to do with barrel time, correct exit time of the bullet, and the shockwave (barrel harmonics).
Once an accuracy node is located:
3, or 4, or maybe 5 thousandths of an inch deeper seating depth will increase barrel time just a tiny amount to allow the exit of the bullet to occur at a calmer state of the muzzle, if that is what's needed, and thus shrink groups.
3, or 4, or maybe 5 thousandths of an inch longer seating depth will shorten the barrel time by a tiny amount to allow the exit of the bullet to occur at a calmer state of the muzzle, if that's what is needed, and thus shrink groups.
It's ALL about timing the exit of the bullet when the muzzle is in the calmest state during the cycles of the harmonics. Roughed in with experimentations with powder charges (changes in speed), and then fine tuned beyond what a powder charge increment of .1 grains can do with very small changes in the actual distance a bullet must travel to exit the muzzle (changes in seating depth).
Mag Length governs everything I do......
One of the most accurate loads I've ever developed, consistantly under 1/4 MOA, was with a 90 grain Sierra HP in a factory Remington .270 win barrel. The bullet jumped .250" to the lands. That's a whole quarter of an inch.
