not that I can think of.

un;ess you can get creative by texture maping the gun to a 2nd skin and enlarging the skin area size, makign the enlarge part transparent then by fixed function UV shift that 2nd skin depending on the view mode your in ( first person vs 3rd person).

But i've never tried it or seen if it could be done that way.

your better off attaching for 3rd person view and view entity for 1st person and and toggle visability as needed that way.