230 grain loads, especially hollow point loads are shorter then typical standard .45 Colt loads.
Snap caps are just that: snap caps. In no way do they replicate real ammo.
For that you'd need Action Proving Dummies. available from Brownell's. These do replicate the exact size, weight, and even balance of live ammo.
In short, like most tube feed firearms, you can't over stress the spring unless you try to jam in rounds when they don't want to fit.
Since your ammo is shorter, the tube will hold at least one more round.