For a .257" diameter bullet, the Greenhill formula tells us the minimum twist required for any bullet length. Using the .82 estimator we get approximate bullet weight in grains.   

Bullet                   Bullet
Length      Twist    Weight
1"             9.9"      122 gr.
.9"           11"        110 gr.
.8"           12.4"       97 gr.
.7"           14.2"       85 gr.
.6"           16.5"       73 gr.   
The ballistic coefficient of the bullet is about the same for all calibers, of the same length. Means that a 25 cal. 1" bullet has about the B.C. of a 30 cal. 1" bullet. 
The longer the bullet, the less it is affected by the wind, and the faster = smaller number must be the twist. For cast bullet rifles the slower the twist the easier it is to get the rifle to shoot-sometimes. 
If it was me I'd get a 10" twist barrel and shoot long-for-caliber bullets; maybe starting with a 110 grain .9" long bullet.
Hope this helps;
joe b.