I just finished slugging the barrel on my WesterField 30-30. I wasn't for sure if it was a Micro-Groove barrel or not but after Sharp's suggestion that if it has lots of grooves then it likely is. From the best I can tell it has 12 grooves in the barrel. That should mean that it is in fact a Micro-Groove. After numerous checks/measurements with my micrometer (not my caliper), it appears that the groove diameter is .309". My cast bullets are dropping from the mold at .310". In my thinking these bullets should be good, (at least in this barrel), as-is with no further sizing needed. Am I correct in this thinking? (Please be patient with me as I'm new to casting and slugging barrels). I forgot to mention that these bullets are gas checked. If I'm good then I can go ahead and work up some test loads and head for the range. Any comments are greatly appreciated.