mhh... IMHO i would buy the adapter, because on my famas the barrel is a bit wobbly, and at every game i watch to it... a 25 cm silencer would probably add more weight to the barrel, causing it to became even more wobbly.... altought i don't know if you have this "problem" too.
I would probably buy the adapter, but this is only my personal taste
sorry if i wrote something strange or incorrect but look at my sign