If you don't seat them any deeper it will be just fine. You may have a problem loading the .308 bullets in cases you have pulled the surplus stuff from, the 7.62X54R is really at least .311, so the new bullets may fall into the case. If you have a Lee factory crimper you may be able to squish the case mouth a little to hold the bullet while you crimp it with the crimping die. The .308 bullets will shoot fine, they may just be a little less accurate, but then if you are shooting tracers I bet you won't care. Larry