the delrin bolt is lighter than your stock alum one, so requires less pressure to move it back and forwards. This generally increases the speed that the bolt can recycle, it also means there is less pressure on the solinoid.
I will have some IPB V2 delrin bolts in stock early next week for the shocker, e-mail me if you want the price.
I will be at MM round 5 in Uttoxetor on Sunday if you want to see or try one.
cheers
Bruce