Re: Straight pull tube gun
I think he means something like the MAK tube gun, but with a straight pull vs a turn bolt action. I am not aware of such, and no one that I know of has made a "modern" straight pull since the Swiss Schmidt Rubin. It is an interesting concept though. Sort of a centerfire biathlon rifle as it were.
I am sure it could be done, but it will have to outperform and be cheaper or no more expensive than a comparable bolt action, to be viable.
Perhaps some of the innovators here will take up the challenge.