338 Whisper - Did I Boo Boo?

[Leadlauncher]

g.day to all,

I recently had a 20" barrel chambered in 338 whisper, or if you like to call it, 338BR remington. I want to try it out for 500 meter rifle silhouette, using 250 grain Lapua Scenars. But I think I might have a problem. It has been set with 1:10 twist. (Is the real whisper twist 1:8?) Do you think this twist is fast enough to keep this big slow pill stabel @ 500 meters?? Any feedback will be appreciated.
kind regards
Leadlauncher

[bufflernickl]

Lead,

measure the length of the bullet and plug your values into this twost rate calcualtor:

http://www.borg.com/~billmohr/maxbullet.htm

I find it to be slightly conservative, but quite useful.

Cheers/buffler