For M118LR coming out of the 20" barrel of an M110, KAC uses 2572fps as the MV value in their Bulletflight iPhone ballistics app. Conditions appear to be standard (59degF, 29.92"HG, 0' ASL).
Yet I have BH 175gr red box .308 coming out of my 20" 1:11.25 twist 416SS triple-lapped AR10T barrel at 2450fps at close to the same conditions (56degF, 30.27"HG, 900' ASL). I use a CED M2 chronograph that is about a year old.
Is my chrono off, is my AR10T barrel that much slower, or is the BH red box just loaded that much slower than M118LR? Maybe it's all three?
I would greatly appreciate any insight.
Yet I have BH 175gr red box .308 coming out of my 20" 1:11.25 twist 416SS triple-lapped AR10T barrel at 2450fps at close to the same conditions (56degF, 30.27"HG, 900' ASL). I use a CED M2 chronograph that is about a year old.
Is my chrono off, is my AR10T barrel that much slower, or is the BH red box just loaded that much slower than M118LR? Maybe it's all three?
I would greatly appreciate any insight.