The NPT 85 grain @ 5000 ft. 59 degrees, 3400 FPS has a stability factor of 1.1, @ 32 Degrees its 1.02 in other words its marginal at best as 1.5 is considered stable. Minimum suggested twist is 1 in 11.5 per Berger. Sierra says 1 in 12.5
http://www.bergerbullets.com/twist-rate-calculator/Looks like 80 grains and length of .810 is your huckleberry. NBT Varmint
