how long does it take to heat bend limb tips?i had the heat gun on the wood for 5 minutes or so and didnt see any change in bending the wood

What wood are you using? Different woods react differently to different types of heat, either wet of dry. How thick is the wood you are trying to bend?

red oak board .5" thick at limb tips

I've never heat bent red oak but I think I'd steam it.