I have a Stanley BR87 hand held breaker that I run with a 763C. I talked to Technical Support at Stanley before I purchased a used unit.
They told me the breaker would handle the pressure, however it requires 7-9 gal/min to operate. He told me if the flow exceeded 9 gal/min it would not hurt the breaker, but it would not operate properly.
I hook up the breaker, start the loader, set the parking break and activate the auxiliary hydraulics. I begin with the loader at just above idle and increase engine speed and operate the breaker. I increase engine speed until the breaker is hitting hard and even.
Note some of these hand held tools must have the hydraulic flow in the correct direction. Make sure you test the lock on hydraulic flow direction before you connect the hydraulics. You can damage an attachment if the flow is backwards.