It's a fool's errand to think you could cut Paradox rifling in the chokes of a 10b shotgun. The barrels aren't nearly heavy enough and there's not even close to the amount of metal needed at the chokes to do the job. A Paradox is not a shotgun nor is it a shotgun conversion.
Here is a photo of the muzzles of my Holland & Holland 10b Paradox to give you an idea of what's going on:
The 27" steel barrels alone weigh 6 lbs. 15 oz., with the gun coming in at 13 lbs. 1 oz.
Here's the H&H ledger sheet:
Here's a photo (top, obviously):
Some bullets:
A few loaded rounds (225 grains 2F, 2 ounce bullet):
Kaboom! A right and a left:
See my first two shots ever on YouTube:
https://youtu.be/saNWxgyOW6cAnybody want to give it a try?
Curl