I almost purchased a 12.5 barrel yesterday, but after reading a lot, it seems that there is non need to go that long, perhaps a 10.5 inches would be perfect (I find the 7.5 too short). Most of the people on forums says 9 is perfect, but since we can't have silencers it's not going to run as good. If there is in fact a can coming soon, I'll wait to see that for sure. A little more kick from my AR would be nice!