I love your last sentence.
I understand that the dedicated target rifle with it's adjustable stock will give an advantage over a sporter stock. That's why I commented that a hunting rifle with a decent barrel/pellet combo and decent trigger ... with a custom fully adjustable stock ... should be no different.
You use a BSA action that you will have worked on and got the barrel where you want it. I think it's then in a Ginb adjustable stock. I'd imagine your rifle will be as accurate as anything and the stock gives you that accommodation of consistent position.
My point really was that there must be loads of standard pcps out there with perfectly good barrel/pellet combos that would give Conor's suggestion of sub 20mm at 55 yards. So all they need is a decent stock and they would be fine for FT or HFT.
So, having said that, is the reason that people don't do that because it's just as 'cheap' to buy a top end target rifle than it is to get a stock for a decent hunting pcp, or is it because it's just the trend to use a dedicated target rifle and you may look out of place, or not up to modern ways, if you are still seen shooting a hunting pcp in a custom stock, even though there may be no difference in accuracy, or points scored?
To be fair, I suppose a hunting pcp action in one of the older ( 80's/90's ) custom FT stocks that were made out of half a tree, probably looks just as intimidating to a newbie as a skeletal style modern target rifle does.