my new ibm has a flat bolt, and it looks like it should have a round bolt according to the serial number.everything else appears to be correct on it. it does not have any rebuild stamps, and it looks to nice to have seen service? is there a company that was rebuildng ibm carbines, and passing them off as non-rebuilds?
NO not that I am aware of. But carbines were rebuilt on all levels of the military not just at the armories. It could have been down at say the company level that worked on it. Then again a previous owner could have changed a lot of the parts on it with IBM parts making it more original.
A lot of carbine owners incorrectly believed that the round bolt was intended for the M2 (select fire) carbine and the flat bolt was just for the M1 (semi-automatic fire) and used a flat bolt to "correct" their carbine. The flat bolt is simply an earlier design and the round bolt is a later design. They both are completely interchangerable and both forward and backward compatible on all makes of USGI carbines. As BQ97 said your other post, your carbine was likely to originally have a round bolt but, like I said, anything can happen. Perhaps your original bolt was damaged and replaced outside of the armory rebuild process. Or perhaps a flat bolt was stuck in the bottom of a bin full of round bolts and ended up being installed months after they were supposedly used up. It doesn't necessarily mean you carbine is not original. You will never really know for sure.
It turns out that IBM is one of the prime manufacturer's that I don't yet have in my collection, so I am jealous. I don't know if you were able to talk the price down, but even at their asking price, I think you did okay.