Since everyone has been making statements based on little fact so far & some conjecture on the PAR design, let me offer the following response from Steve Troy the CEO & owner of Troy Industries / with whom I communicated several minutes ago.
"The fluting is used to keep the case from sticking to the chamber wall making a manual extraction difficult. This is never noticed on a semi auto as the gas expanding in the carrier does all the unlocking and pulling. With the pump we had to override the out of tolerance wolf ammo that was coming in the country that caused a issue in semi guns as well as our pump. There is nothing wrong with flutes done properly in a stoner bolt system, other companies have incorporated them on their semis and full autos as well. I'll leave you google Jedi's to figure out who."
For the time being that should answer some questions & no doubt kick off other-ones...
gadget
I'm going to disagree with Troy, but because I'm not an "engineer" of course my opinion means nothing.
I have stated before, if the flutes interfere with the case rotating to 'break the gas seal' like a normal rotating bolt head, then the extractor claw must grind around the bolt head (as there will be rearward pressure from the action) to unlock and then it can pull the case out of the chamber.
I have NEVER heard of any rotating bolt head rifle that uses a fluted chamber. Of course HK's are famous for having it, but again they have a 'strait-pull' style of extraction, and they need something to keep the case from sticking to the chamber walls. I know there are other rifles with fluted chambers for this same reason as well. (For example; the FAMAS) In this case, it works very well. Quite convenient for them to say "google it!" and let people endlessly search for some random guns that had a fluted chamber and rotating bolt head, that may or may not have ever been in full production. Would love to hear of these common firearms that this exists in!
This seems like Troy sticking to their engineers opinion rather than using some logic or sense. A chamber on the looser side of SAAMI spec, or chromed bore would also aide in extraction of steel cased ammo. Or they could be like EVERY OTHER gun maker and say "Don't Use steel cased ammo".... ESPECIALLY out of spec Wolf ammo, who even designs a gun to work with out of spec ammo??? (I understand catering to the lowest common denominator but this seems dangerous, designing a rifle to shoot out of spec ammo)
I would be much more interested in someone taking a chromed AR barrel (if it indeed is compatible) and putting a sleeve over the gas port to close it off, then seeing how it works with a smooth unfluted chamber... Or a long-term test on extraction between the fluted and unfluted 300 blackout rifles.
