Can I inject plastic in a RTV mould? Will the interior of the mould get deformed by pressure?
RVT silicone is commonly rated by Shore Hardness. some grades are hard and heat resistant enough to be used for centrifugal casting of low temperature metal alloys (aka white metal).
However in practice for plastic casting they are best suited to 'cold cast' resins such as Polyester, Epoxy and especially Polyurethane.
Generally injection moulding is specified for high volume production using rigid steel dies and for low to medium volume production filled resins are more practical and can provide equivalent or better mechanical properties.
If you can provide more details of your application we can give you more specific advice.
You can certainly do very good quality castings, in terms of both detail and mechanical strength with gravity casting of PU resins in RTV rubber moulds in moderate quantity without needing injection moulding.