I'll say it again, I'm certainly no proponent of taking a pristine high value collectable or even low value rare high condition gun, and modifying it, I will modify my mostly bottom-feeding guns to suit me and sleep well at night.
Actually, I don't bother to touch the cones or chokes of most of my guns. I just received a nice little 20g Grade 3 NID, factory SST, ejector. back from restoration by Gunter Pfrommer. (Yeah, I know some of you will want to fight about restoration too. Well this one had one leg in the junk pile already). It doesn't have, nor will it get, long cones.
I don't advocate anyone modify their vintage gun with long cones or open their chokes (my modern tight and tigher 28"/28g Repro will keep its chokes and cones as is). But, I do know that there is a performance advantage to be had. To say such things don't exist is just ignoring facts. To say they are only for someone of a particular level is as rediculous as saying you need to shoot a predermined qualifying score before you're allowed to own a certain gun.
If anyone wants to pursue testing of long cones for themselves, I have a couple reamers I would modify your test barrel with to support your curiousity.
