If your still in doubt contact CVA.If they recommend staying at a 300gr bullet or below they must have a documented reason why.I'm sure they have a technical advisor at their facility you could talk to.Because someone shoots that load and hasn't had a problem doing so,it doesn't mean it's safe to do.I recommend staying within what CVA or any manufactuer's recommendations. These guns are tested and rated for safe use within their guildlines.

Ruger Redhawk