QuickLoad thinks that load would only generate 870fps if standard default barrel friction is included and that's without considering any potential back-pressure from the can.
With default case capacity and OAL, it thinks that load is just 68% case fill, which would be below IMRs starting load calculations.
Real guns almost always have more case capacity than SAAMI standard so it's almost certainly even less than 68% and even lower velocity.
It's hard to say where the line would be and you'll only be guessing without a chrony, but 1,200fps should be somewhere between 11.5 and 14.5gr
10.0gr is just too low.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.