11-02-2023, 05:25 PM
When Bill did the initial and continuing testing with 6.5 Grendel, which included many trips out to New Mexico for high sand and dust, plus long range, he found that the 20 and longer did well with 1/9 twist.
For 18 and less, he preferred 1/7.5 twist.
You can still get by with 1/8 twist in 18 barrels shooting to a certain distance which is primarily determined by your bullet choice, mv, and density altitude.
Lower elevation with thicker air conditions are best countered with faster twist if you want gyroscopic stability to help push into transonic mach range.
I have had better-than-expected results at 1000yds with 1/8 twist 18 Lilja barrels at 6300ft elevation.
I need to shoot some more 4400ft elevation with 1/8 twist to see if Im coming apart there.
With my original 16 AA barrel/bolt combo build (1/7.5 twist), I had surprisingly-predictable impacts at 1200yds with 123gr A-MAX at 4400ft elevation in the summer.
For 18 and less, he preferred 1/7.5 twist.
You can still get by with 1/8 twist in 18 barrels shooting to a certain distance which is primarily determined by your bullet choice, mv, and density altitude.
Lower elevation with thicker air conditions are best countered with faster twist if you want gyroscopic stability to help push into transonic mach range.
I have had better-than-expected results at 1000yds with 1/8 twist 18 Lilja barrels at 6300ft elevation.
I need to shoot some more 4400ft elevation with 1/8 twist to see if Im coming apart there.
With my original 16 AA barrel/bolt combo build (1/7.5 twist), I had surprisingly-predictable impacts at 1200yds with 123gr A-MAX at 4400ft elevation in the summer.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com