I have an IBM in mint condition that I got from the CMP. There are 4 other members of my club who got M1 carbines also. We all get about the same groups. At 100 yards your doing really good to get fist sized 4" groups. 6" groups are pretty common too.
This is not bad. Shooting like this, you can hit a clay pidgeon laying on the 100 yard berm most of the time. And when you miss, you are missing really close. They are great little carbines.
I have no experience with Fulton. But I have seen their site before and they look pretty good.