I used the vice clamp method on my FCU as well with success. I took virtually all of the vertical play in slide to frame fit out, I only left a little bit of lateral play for reliable function. Had to file down / refit the FCU rails to slide rails afterwards, otherwise the slide would bind terribly on the FCU rails. However, it had a rather cosmetic effect, I get pretty much the same groups as before, with slow fire at 25m I can do about 3" if I do my part, more or less the same as before. My barrel to slide fit was good from the get-go, no discernible play when I push down on the barrel hood. Honestly the biggest effect on the size of my groups was achieved by a trigger job - I managed to get down to 2.5lb with about 3.5mm reset and buttery smooth pull, pretty goodtrigge if I say so myself. But for some reason, I am still less accurate with my legion at distance of 25m or more than with a Glocks, XDMs or 1911/2011s for some reason. All in all, I wish the legion had a bit more accurate barrel with a tighter rifling (I found out it shoots best with .358" bullets, my other 9mm pistols are good with .357"), but for the intended purpose (IPSC shooting), it is accurate enough.
X5 Legion accuracy
in Sig
Posted
I used the vice clamp method on my FCU as well with success. I took virtually all of the vertical play in slide to frame fit out, I only left a little bit of lateral play for reliable function. Had to file down / refit the FCU rails to slide rails afterwards, otherwise the slide would bind terribly on the FCU rails. However, it had a rather cosmetic effect, I get pretty much the same groups as before, with slow fire at 25m I can do about 3" if I do my part, more or less the same as before. My barrel to slide fit was good from the get-go, no discernible play when I push down on the barrel hood. Honestly the biggest effect on the size of my groups was achieved by a trigger job - I managed to get down to 2.5lb with about 3.5mm reset and buttery smooth pull, pretty goodtrigge if I say so myself. But for some reason, I am still less accurate with my legion at distance of 25m or more than with a Glocks, XDMs or 1911/2011s for some reason. All in all, I wish the legion had a bit more accurate barrel with a tighter rifling (I found out it shoots best with .358" bullets, my other 9mm pistols are good with .357"), but for the intended purpose (IPSC shooting), it is accurate enough.