I have 2 Navies, Uberti, with Kirst cylinders and 2 with R&D (gated) cylinders. I shoot 38 Special with 148 gr. Hollowbase Wadcutters. Hornady bullets lead a bit. Better are the Speer and Remington HBWC bullets.
At Cowboy ranges, and indoor range distances (15 to 50 ft) they are very accurate. At long range outdoors, like 50 yds. or more, the slow roundball twist of the rifling shows up as there isn't a fast enough spin on the long bullet for long range accuracy.
I think the hollowbased bullet being nose heavy has a bit of "arrowhead" effect helping, but not enough to make the bullet stabile at long range.
For real accuracy, R&D will reline the bores to .357 and supply a cylinder chambered for the 357 diameter bullet. The 357 cylinder is throated for the 357 bore size, the 375 chamber is bored straight through to allow the hollowbased bullet to open up for the 375 bore.Check R&D's website for parts and prices.