Probably bulls to use on 2 or 3rd calvers. You might contact the breeders of AT Rock and Roll ... they bred the sire as well. Abertees Professor is still breeding females at Masonic Homes in PA.
Just checking the American Shorthorn search site http://search.shorthorn.org/default.aspx
it looks like AT Rock and Roll Train has good birth weights. His shows as 82lb, his sire as 86 and his dam as
85 lbs. More importantly his calves seem to range from 66 to 86 with most in the 78 to 82 range.
Rock and Roll Train's calving ease is 2.2 (top 20%) BW 0.8 (top 25%) and $CEZ 19.03 (top 50%).
I suggest you follow Sue's suggestion and contact someone that has used the bull or those bloodlines but by the numbers he looks good (thumbsup)