I have a couple dozen transferable machineguns that I have collected over the past 20+ years buying roughly one machinegun per year as machinegun collecting has been one of my hobbies/interests.
I own an M11/9, M11-A1, full size Uzi, MP40, S&W M76, Norrell 10/22, Reising, 1928 Thompson, M2 Carbine, two M16 registered receivers, AC556K, FNC, AK47, FAL, 1919A4, M60E4, an HK21E / HK23E. I also have a Steyr AUG registered auto-sear/hammerpack, two M16 registered auto-sears, and three HK registered auto-sears that I move around to probably another two dozen+ AUG/M16/HK host guns which probably brings my effective total to 40 to 50 different distinct machineguns.
Its unfortunate that machineguns have gotten so expensive due to 922(o) and that accelerated pricing precludes more and more folks from being able to purchase and enjoy them.