[Iowegan]

BladeRimfire, The optimum B/C gap for centerfire revolvers is .006 ~.008". Why? Because endshake will grow with the number of rounds fired, When endshake wears to its maximum allowable of .005", the cylinder will still not rub on the barrel. For rimfires, this is not as important because it would take many bricks of ammo for endshake to reach .005" so the optimum is .004~.006". When the B/C gap is tighter than .004", fouling on the face of the cylinder will cause the cylinder to drag on the barrel. Of course 22 WMR ammunition for your Single-Six revolver is only made with jacketed bullets so it won't get lead fouling on the face of the cylinder, but it will get powder fouling. Also, if the B/C gap is too tight, it makes it harder to install a cylinder after cleaning. Another issue that doesn't affect 22 LRs much is top strap flame cutting. When a B/C gap is too tight, centerfire or 22 WRM ammo will concentrate flame cutting to a narrow line that gets much deeper than with a wider gap.

B/C gaps are one of those things an owner can see and measure so to keep with Internet expert recommendations, the tighter the better. In reality, .004" B/C gap is much better. Just one more comment .... when the Gun Control Act of 1968 was passed, it made official definitions for pistols and revolvers. Pistols are all handguns that do not have a rotating cylinder. So, your gun is a revolver, and a nice one at that.

 

[Iowegan]

wprocy, Good question .... the gunsmith answer is: when the cylinder is wedged forward, you get the "actual" B/C gap. When the cylinder is wedged back, you get "total" B/C gap (endshake = total B/C gap minus actual B/C gap). There's a reason why the B/C gap is measured with the cylinder wedged forward .... when a round is fired, the friction between the bullet and the cylinder throat will cause the cylinder to move forward to the tightest B/C gap.

Here's a tool I use when measuring the B/C gap and endshake. It is a brass rod that has been ground to a taper. Place the wedge between the recoil shield and the rear of the cylinder to measure "actual" B/C gap. Place the wedge between the front frame and cylinder face to measure "total" B/C gap.

Note: This revolver has a .004" actual B/C gap and a .006" total B/C gap, so endshake is .002".