[Unclenick]

Oakfloor,

They can indeed split. There is about 0.007" difference in the diameters of the two rounds. However, I expect most brass (except I would avoid nickel plated) should tolerate that much expansion if the pressures are kept low and they aren't ever sized back to original diameter.

I note Hodgdon only recommends loads using 231/HP38. This is for ease of consistent metering of the very small charges (2.2 to 2.5 grains with lead 145 grain bullet). That's likely a sound recommendation.

The top break actions are not terribly strong, but the pressure limits for the round are low in general, so even a stronger design will not have been proofed very high.