I hear, you hanshi. The .311" was the firs tone I bought and shot for a while. I was using the mattress ticking we'd found that measured .0235" compressed in my calipers.
It was down to about .020" in the mic. The little balls loaded very easily, even thought he barrel had very narrow grooves and wide lands- opposite what many (including me) like.
It shot OK, but that's it, about 1" at 50 yards for 5 shots. I could not get it to shoot tighter.
I bought another Lee Mould, casting .320"x.320". It was their .319" mould. These seemed to load almost identically and they literally shot the same 1" groups from a rest at 50yards.
So - if I ever get another .32" I won't waste my time with the smaller balls as I no longer have that mould.
The larger balls have the potential to shoot better and that is good enough
for me.