Not much difference.
I am guessing the grooves on the TSX reduce pressure, hence velocity slightly lower?
This seems reasonable.
Seems to be the case in a select few. I know in my .223AI I could only get 3200fps out of a 50 grain TTSX.
I stepped up to a 55 grainer ( with one more driving band and hence more bearing surface...) and voila! 3500FPS
