I have a Winchester 1300 NWTF, when I originally patterned it with #5's the pattern was kind of light at 40 yards.  I put a aftermarket .665 choke on it (do not remember the type and name is not on it) the pattern was insanely tight.  I have never seen a tighter core and overall 30 " pattern with 3" 1 3/4 Winchester Supreme High Velocity #5"s.  I cannot imagine what winchester LB's will do out of it.  I'll give you a heads up, I thought I read somewhere that the LB's did not kick as much, I would use them, the 1300 is brutal with the recoil.