I am in the last stages of rebarreling a Enfield to 460 weatherby (action work done) and would like to know the best twist rate to order. I am interested in using ultra heavy up to 720 grain cast bullets and do not think a 1 in 16" is fast enough to stabilize them. and would welcome some expert opinions on a suitable twist rate that would work with 400 to 720 bullets. Thank you for the help.

There are other Twist Rate Calcoualors on the web as well. This one seems to work OK. Brian

http://www.bergerbullets.com/twist-rate-calculator/

I have a 1-10 on my 21" 458 Lott and a 1-10 on my 460 Wby. I have shot 600 gr jacketed lead bullets in my 460. I think you can get a 1-10 from pac nor. 600 is obviously not 720 but when shooting at 300 yards they were still hitting dead strait. What are you going to use your 460 for primarily, what is the barrel length?

1:10 - 1:14 lead bullets are shorter, generally, than jacketed