My links are messed up in my first reply, so here goes ...
Do you have the Savage 300WSM controlled round feed or push feed bolt head? The controlled round bolt head will have a standing ejector in the action. You will have to remove it if you are converting from controlled round feed to push feed bolt head.
You can go to this link, put in the Savage serial number, and it will give you the part numbers of all the parts on your rifle.
https://store.savagearms.com/partfinder
MidwayUSA.com and Numrich sell Savage parts (
https://www.gunpartscorp.com/), or you can buy the entire bolt directly from Savage if you want. Savage will ask you to sign a release form and send it back though before they will sell you bolt parts.
If you buy an entire bolt or bolt head make sure you buy an extractor, extractor ball,and extractor spring and an ejector and ejector spring. New Savage bolt heads generally do not come with these parts. You will have to install them.
Gun Shack sells a nice kit (
http://www.gunshack.com/savage-parts/savage-bolt-head/savage-bolt-head-parts]) with all the small parts for your bolt head and bolt heads.
I needed to replace one of my model 16 WSM bolt heads and firing pin assembly. Firing pin was piercing primers and the blow back damaged the firing pin and enlarged firing pin hole in the bolt head. I bought the parts from Savage as they were out of stock everywhere else.