Point of information:
Kilns, and all other electrical devices are rated at their top amperage, or "amp draw" depending on its use. Motors in electrical devices can draw up to 125% of the rated draw when starting, and are rated separately for that.
When planning wiring, or trying to size a circuit breaker, one should always use a figure of the amp draw being a maximum of 80% of what the circuit needs to be.
Therefore, a device such as a kiln that draws 50 amps should be on a circuit of
50= 80%, therefore 50=4/5, or about 62.5 amps.
A 60 amp breaker will NOT do. You would need to go to 70 amps or better to accomodate your "load" or amp draw.
Higher is always better. Don't forget that you also have voltage loss through the wire. The longer the wire has to be, the greater the voltage loss. This also leads to higher amperage draw as well.
That's what the National Electrical Code in the US says, anyway.
If your wire is of sufficient size, it is a simple matter of replacing the circuit breaker. If it is NOT, then you will (yes, WILL) end up overheating the wire and cause a fire (and not in the kiln).
Be safe, spend the money and do it right.
Best, Wayne in Key West