An extract from
This Link explains:-
Effect of Weight on Glide
"It is important to note that weight is not a factor in the L/D equation. Therefore, it is not a factor in how far an aircraft can glide. An aircraft always achieves maximum glide at a certain angle of attack (CL).
When gliding for maximum range we must always operate at the optimum CL which produces the maximum L/D ratio. Therefore the heavier aircraft will have to fly at a higher speed, while the lighter aircraft will fly at a slower speed. Both aircraft will be at the same angle of attack however."
Obviously force landing at the lowest speed (and therefore lower weight) and without live weapons is preferable!