Aw jeez, now I have to dig out my IBM. I don't think it has a bayonet lug, but it is 600 miles away. I also just snagged an Inland, so I will have to check it out. If either prove to be above the lamp stand class, I'll post some pics.
IBM did not make M2 receivers so you're likely more than safe, plus there is nothing wrong with having a bayonet lug. Most of the rebuilt carbines have one. Only Inland and Winchester (very, very few) built M2 receivers.




















































