I would test loads with a Speer or Sierra spitzer boat tails to get an idea of what loads shoot well for your rifle. Once you have some load parameters switch to the Siroccos and drop back about 2% in charge weight as the Siroccos generate more pressure than most bullets. Load to the same length as the cheaper bullets and see if that works. If not seat to mag length and then bump them back until you at least get close to the accuracy of the other bullets you were using. I have heard that bonded bullets are less accurate than plain cup and core. Not sure why but possibly the flux or bonding agent is not as uniform as the bare lead against the jacket.

I am playing with 150 BT and starting to get good results with R16 and R26. My previous loads were with R22 and they did well. Lots of powders work in the 300WM. I wouldn't worry too much about velocity as anything at or above 308 levels will be plenty for deer. The Siroccos may not kill as fast as the Power Points as the Sirocco is a tougher bullet.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli