NO,
Framing nails are not strong enough (Width in diameter) to be used for installing joist hangers. You need to use approved joist hanger nails.
If you are 'dead-set' on using a pneumatic gun, there are two choices:
1.) Metal fastener gun: Several maufacturers make guns just for joist hangers and brackets. They have a guide point tip to align the gun with the hole and then you can shoot the joist hanger nail into it.
2.) Palm nailer: inexpensive choice.
Tho, if you are good at swinging a hammer, it can be done very quickly 'by hand'....the old fashioned way....