Iwouldn't touch the LTR that you already have. If you want a 300SAUM bad enoughI would just get another LTR. However it still comes with a 20" barrel and even the short magnums need at least a 24" barrel to effectively gain the added performance they can offer. It will offer more performance than the .308 but hardly what is printed on the factory ballistics charts. Basicallythe SAUMwill loose a higher percentage of velocityper inchthan the .308 will.