Quote Originally Posted by SRG720 View Post
OK because I'm just assuming a smaller yield 100 kt warhead aka w76 would be smaller and much lighter than a warhead like the w88 at 475kt. Also, I think the payload of the missile to the range of the missile is also an important factor. Ie the heavier the payload the lesser the maximum range.
Yep, it's all in the Ideal Rocket Equation:



Since you're holding the rocket type itself constant, the actual total thrust is constant. The final vertical velocity will therefore be roughly proportional with the mass differential between warheads so the rocket's range will also be affected by the increase or reduction in payload mass. The exact effect on the max range will also be affected by any additional engineering done to accommodate the change in warheads that increases or decreases the total mass of the payload complex.