Therein lies the problem - what kind of loads did he use, what is the bolt made from, etc. One could guess that it is the same as the other Saiga rifles, since materials procurement would be simplified. THEN AGAIN it would be cheaper to obtain something less strong since it would probably save costs. I don't know.
If the trunion DOES look like a 7.62x39 trunion, then you can reasonably expect to use a 7.62x39 parts kit and build from that.
A thought - on the books it would still be a shotgun, correct? If so, then one should consider the need for an 18" barrel no matter the caliber! Otherwise it would be *classified* as a short-barreled shotgun! *oops*
I wonder if there are any special requirements for "reclassifying" a shotgun as a rifle? Those huge builds that Hubel is working on are all technically shotguns, and as such are not classified as Destructive Devices. I'd be concerned about using the shotgun platform as a base for several reasons.
the trunion looks exactly like a AK trunion with the area for the bullet guide milled out. the bolt if anything appears stronger. the lugs are actualy bigger. as far as I know tony used factry loads in his gun. all he did was rebarrel it to a rifle barrel. the barrel has a shroud over the top to guide the round downward BTW. Tony is a smart guy and im sure he tested it out pretty well. he will answer emails and is on differant gun boards from time to time im sure he would answere some basic questions. his friend or employe eanswers for him as well some times.
as I recall they were some how redesignated as a rifle due to the fact that he is a manufacturer. but I suspect your right that if kept as a shot gun then would need a 18" barrel unless the fact that that adding a rifle barrel makes it a rifle. the h&r handi rifle and oters come with shot gun and rifle barrels . i think there loged as a rifle however and as I recall they will not put a rifle barrel on a shot gun reciver but I think that was a strength issue. I have a savage combo gun that is a rifle on top and a shotgun on the bottom. not sure of the law. the saiga uses a standard width reciver so a new reciver could be added and just use the parts from the shot gun but the have the serial number on the trunion so if it was ran it would still likely come up as a shot gun HMMMMMM
here are some pics of my bolt and trunion as well as a 500 S&W case in the bolt. it would take a slight amount of extracter work and a litttle of the bolt face tab to make it work.