I had good tests with the Snover in my Browning at 100 with really low SDs but I went with a different bullet for BPCR. Here are some folk's views: (You need to Login or Register to view media files and links)
Lyman rates it at 400 grains but with 20 to 1 will be closer to 410 grains. I suppose I should add that in an alloy test series of 30, 25 and 20 to 1 at 300, that 25 was much better than 30 and 20 was somewhat better than 25.

Miller Gyroscopic Stability for 18:1 twist barrels and .409 BACO Bullets:

1.53 400 grain Money 1.400"
1.69 415 grain Postell 1.370"
1.46 420 grain Money-Tapered 1st. Band 1.450"
1.71 420 grain Spitzer 1.370"
1.70 430 grain Creedmoor  1.385"
1.70 430 grain Creedmoor-Tapered 1st. Band 1.385"
1.74 430 grain NASA 1.375"
1.66 444 grain NASA 1.413"
1.39 450 grain Money-Tapered 1st. Band 1.510"
1.45 460 grain Creedmoor 1.500'
1.45 460 grain Creedmoor-Small Driving Band 1.500"

Where an Sg of 1.4 or less may tumble somewhere down range (or sooner with lower temperatures or higher atmospheric pressures) because the rifle twist is not fast enough.
Long distance shooters (1,000 yards) prefer a Sg of 2.0 to 2.5 to over spin their bullet to compensate for drag over longer distances.

Heavier bullets are less susceptible to wind drift and travel further distances due to their Kinetic Energy which results from the greater mass (weight).
But if you get a bullet that is too long for your twist you will have a Sg less than 1.4.
Traditionally barrel twists are selected to have a Sg of 1.5 to 2.0 for the length of bullets to be used in the rifle.