Looks like I'll be taking the bayonet to the skeet range today...
The simple answer is 'no, it will be fine'. Because a firearm kicks - back into your shoulder - folks commonly believe that everything kicks backwards. In fact the opposite is true. The projectile, shot, slug, gas, etc comes flying out of the muzzle which pushes the shotgun backwards - just like a rocket ship. Therefore most things on a firearm move forward. Your bayonet is standing still and then the gun goes backwards. This is the same as if the bayonet had been pushed towards the muzzle.
This is why accessories should always be be mounted forward, particularly rail-mounted optics. They're going to fly forward when fired, so go ahead and mount them towards the front. This way they have nowhere to go.
So your M7/M9/OKC goes forward, not back into the lug. And I don't think that lug is gonna snap off.