Another wad question

[Rio Grande]

Given that many cap and ball revolvers have barrel groove diameters that are larger than cylinder chamber diameters (!) would using a wad under the round ball or conical increase velocity by achieving a better gas seal?
Maybe some of you chronograph owners have run tests?

[troy_mclure]

ive found no difference with powder/wad/ball/wad, powder/ball/lube, powder/wad/ball/lube, powder/wad/ball.

velocities were 6 shot average, all averages were within around 50fps.

[Rio Grande]

ive found no difference with powder/wad/ball/wad, powder/ball/lube, powder/wad/ball/lube, powder/wad/ball.

velocities were 6 shot average, all averages were within around 50fps.

No difference. I guess that answers that. Thanks.
I would have thought there there'd be some variation.

[troy_mclure]

me too, i figured the weight of wads or lube would produce more pressure, or lower velocity. something. the chambers are tapered on my euroarms .44 so i dont get the lead ring or really tight fit most do.

[Omnivore]

The theory is that the ball will obturate (deform) into the rifling under the intense acceleration. It seems to work, as I've recovered balls fired from my Piettas, and they show full engagement with the rifling after coming out of a chamber that's several thousandths smaller.

I've never heard an explanation as to why anyone makes chambers smaller than the groove diameter, as most BPCR or cast bullet smokeless loaders will tell you that best performance is obtained by using a bullet that's one or more thousandths larger than groove dia.

Uberti sizes their chambers the same as the bbl groove dia., whereas some of the more hard-core cap and ball shooters ream out their chambers to two or three over.