Pardon me for sticking my nose in...
This sort of reminds me of the old line: We've established you're a whore, now we're just negotiating the price.
What I mean is, when any modern production items are allowed, the authenticity is compromised. The rules could have stated: Only authentic period firearms, no reproductions. Requiring authentic Henry & Winchester rifles from prior to 1899 would certainly solve the authenticity issue. That would also make this game unavailable to a large percentage of the current membership. So, it seems to me that now we're simply negotiating over how much loss in authenticity is acceptable. I suspect many people are more tolerant of less authenticity when it is because the shooter is new, or poor, etc - as long as they aren't competitive. We want to be inclusive - as long as they don't beat us in the standings...
This all seems like the natural result of having a game that includes a timer. If this game was based on pure accuracy with no speed component, then we would probably be discussing the use of heavy barrels, modified grips and other accuracy mods. In some ways, I guess this is the difference between reenactment and CAS - when there is a component to the game other than authenticity, the result will always be something less than authentic.