My .22 Hatsan AT44 10 had a really tight choke and was
seriously inaccurate.
I machined 1/2" off the end and it ended up as accurate
as my S400 in a shootout, so i sold the 400 and kept the Hatsan...still have it.
I also use a 4.51 sizer on Crosman ammo for my TX and
matches the JSB accuracy at 25m.
5.50 sizer..?.