I don't think the plastic is hard enough to dent the primer.
Does anyone know?

One at a time. Not sure if the plastic will dent the primer, but I wouldn't try it. The plastic tip will set back into the tip of the bullet, rendering it approximately useless.

Stick with round nose bullets.

As previously stated, you would be ok if you loaded them one at a time, in other words, if you only had one in the chamber not stacked in the tube.

Unless you deep seat the bullet, the OAL will be to long to cycle thru the action.
Besides, you only need one shot. Right?

If a soft lead tipped bullet will dent the primer a poly-carbonate tip sure as Hell will. I recommend gettinng your affairs in order before trying this.

Not only NO! but HELL NO!!!!!

Assuming you realize that these plastic tips are harder than lead tips, I'll let you answer your own question.

Do you think if someone was stabbed with a hard plastic knife that they could be injured? You bet your a$$ they could.

RSY

I think the plastic tip is hard enough to dent a primer. You could load one in the chamber and one in the magazine, so you'd have a two-shot capability. Twice as good as a single shot!!