Re: slash 10 oz heavy buffers
Yes...assuming you are talking about the XH .308 rifle buffer and depending on how your rifle is set up and how you are running it.
If you aren't running the gun suppressed (or running some HEAVY reloads or cartridges like the WSM/SAUM/.338 Federal/etc.), I don't think that you necessarily NEED the .308 XH buffer though. The other exception would be an overgassed factory gun where you want to slow down the action some or otherwise reduce perceived recoil.
The standard 5.4oz rifle buffer will work well for most non-suppressed, .308 semi autos.