Drilling out the RN plug did the trick to seat the FTX bullet. I used a G bit (0.261") to fully clear the flex tip and hit the "meat" of the copper jacket.

It took 10-15 min's to set the plug in a vice and 2 seconds to drill the hole while I held my breath. It turns out the plug material (steel) was VERY soft.

I seated about 48 bullets and got just a faint ring around the bullet where the plug made contact.

I could get real uptight about it and use some valve grinding compound on a sacrificial bullet(s) and lap the plug to the bullet. It might take two or three bullets. Its the copper vs. steel thing.