Both of my Lymans have the barrel stamped on the right side. If it is says Great Plains Rifle it is 1:60 twist and if it says Great Plains Hunter it is 1:32. If your barrel isn't stamped then you will have to check the twist because the lock, stock, etc are the same on both models. Only the twist rate is different..If you have a jag that turns it is easy to check the twist. My Lyman Hunter loves the Hornady Great Plains bullet 425gr. with 90 to 100 gr powder .( 54 cal)