I'm not sure what the thickness or in this case thinness of the rim material of the bolt head has to do with anything, there is plenty of steel there to deflect gasses from a pierced primer which is about the worst it would see as it only holds the rim of the cartridge. So what's the big deal?
Look at this picture and see how the design protected the shooter from gases and the shrapnel the extractor became. This is a Sako 2 lug bolt action. When guys have the Sako extractor installed on a 700 they do not install all the the system. They fail to install the 'bolt guide' which is really more of deflector.. With the conversion on the 700 there is no 'bolt guide' to deflect or stop anything. It is all free to blow right out. There have been injuries and at least one death with this partial Sako extractor conversion on 700's in the US.




















































