The back of a small thick knife with a saw ridge is good for separating the joints of deer or sheep. It won't go through bone but cartilage and tendons give way fairly quickly.

The bayonet to use is the needle type with three edges - the modern ones are quite tame by comparison. Stick that on the end of a good long rifle and you can see why 'They don't like it up 'em, Sir, they don't.' (Cpl Jones, Dads' Army)

You can also see why the entire cast of extras went on strike when instructed to charge towards the cameras, downhill - with bayonets fixed - in two ranks. Sometimes directors are wrong - it is just that they can't see it. When the camera men realised the possible/probable results they went on strike too. It was only student film making and the props were just wood - but even so -

The edges give the bayonet the rigidity of something heavier, for multiple use.

I got a close up - with a real bayonet - I was the only one with small enough hands. Even in the 1970's it was obvious that people born after the war (WWII) were far larger than those who fought in it. Trying to depict older times using exact replicas or the real thing is difficult if all your young men are too tall for your 'good' props.

There was the same problem in Shogun, I believe. All the Japanese were too tall and the European 'hero' spent the film standing on boxes or walking along planks.