DW,
My rifle is a Winchester Low wall with a #2 full octagon barrel.  It was bored out to about 5/8" - I could measure to more precise.   

The liner is Lilja that was cut and crowned before it was run into the reamed barrel, so getting the thing crowned was easy - it was done before it was put into the barrel.   

I did put a very thin brass tubing in the muzzle and  held it with a set screw to collect the fouling that accumulates inside the back bored section, but after a while, I got tired of this, so I just regularly swab it out with a shotgun rod and brush and good solvent.

All I can say is that it is the single most accurate rifle I own by a good margin.  Although built to be an offhand rifle, it will run with anything from the bench as well.  So, I guess I would say that, no, I don't think there is a turbulence issue.

Brent