Handloads for a Bushmaster 308 & 223

I recently purchased 2 Bushmaster Rifles (one in 308 and the other in 223). I was reading the disclaimer on their website about Warning: Do not use handloads or reloaded ammo in the Bushmaster Rifles because of possible damage and will void the warrantee. Does anyone out there handload for a Bushmaster Rifle and know the specifics of the company's concerns. Any info would be great and I will post this question in the Reload Forum as well. Thanks, Mike