I could only assume, you're using a CVA. They do love PB's! I've never seen another brand that likes them all that well.
You are correct in that, PB's indeed have a bigger O.D. than a sabot. As you say, the Hornady's etc. are somewhere around .451 or .452 actual bullet diameter.
Even with the PB's, there will still be a slight amount of plastic left behind as the tail end has a plastic "ring" that expands when the powder is fired (Minie ball concept). In my experience and with most of the other CVA shooters/hunters I know, (more often than not) there is no exit wound
. This would indicate to me the game is absorbing all of the energy from the round or knock-down as you mentioned. It makes sense, bigger bullet. I've also hear guys complain about this! (Huh)? This being said, I also know of one guy (CVA shooter) who swears by the Barns sabots in his gun.
I do like the Barnes (in a T/C) and they expand just like they claim. I do get an exit wound twice the size of the entry wound. Devastating performance.
I can tell you're a guy always wanting to try something different and looking for the almighty excellence in performance and accuracy. Nothing wrong with that, I'm the same way and I admire that!
I do have the luxury of living 3 miles away from on of the best PB shops in Michigan. Guy who owns it is a life-long friend. (Bill Hammond of Spring Brook Trading Post). He takes a ton of things in on trade. When most of these guys trade something in, they also leave behind everything with the gun.
He can't sell half a box of sabots/powder/bullets etc. so he gives them to me to try. I report back to him on how everything does. Great situation as I don't have to go buy all this stuff only to find out (in most cases) It isn't all that great after testing it in numerous guns. Once in a while I find a combination that gets my attention! I also go with Bill to the big BP competition shoots with his truck and 40 foot (store on wheels) trailer. I see first hand exactly what all the big shooters are doing.
Quick example: I ended with a partial box of 50 cal. 300 gr. Hornady FPB's recently. Looked pretty cool! No plastic, a copper jacketed lead round. Very much like the PB's only metal instead of plastic (modern Minie ball again). The box said, "easy to load, accurate, no lube, hard hitting, no need for a plastic skirt"! I thought, cool! Something worth trying! I'm here to tell ya, I about popped a beanie trying to get on of those rounds down the barrel of my T/C. That was so hard to load, I didn't even want to try it in anything else! After the fact I checked them and they mic out at a whopping .506 at the base (flared end). Holy mackerel, no wonder I had trouble!
My advice... if you have something working well for ya, stick with it!
If you want to try other things, find another shooter who uses it, get 3 rounds from him and try 'em before buying any. Or... split a box with someone if they also want to check something out.
All the best to you and Merry Christmas!