Barrow Roll said:
For all of you just getting this game now, you should pretty much do this. In fact, don't even buy the Riot Gun. The first shotgun is good enough to last you until the Striker. You only thing you really need to be using a shotgun for is close range crowd control. Damage output isn't important, knocking everyone in front of you on their asses is.
On my first few playthroughs I didn't even buy the Striker at all. Just upgraded the shotgun all the way through the game. It's honestly "good enough" for every situation, though the spread-fire capabilities of the Striker are good for someone who struggles with crowd control.
Honestly, this is my preferred way of getting weapons:
-Buy Red9 and stock, and don't upgrade the regular handgun beforehand. Sell Punisher.
-Use the first shotgun all the way through the game.
-Skip the Rifle for the entire village sequence; buy Semi-Auto Rifle as soon as getting to Castle.
-Obtain free Broken Butterfly at Castle.
-Take free Rocket Launcher and use it against Verdugo (takes really good inventory discipline).
And that's basically it. I prefer the Red9 to other handguns because of power and it's general awesomeness. I get that baby to 6.5 exclusive power right before leaving the Castle. I prefer just upgrading the regular shotgun because you get it for free in the beginning and it remains powerful enough to handle situations where it's needed. For my first professional run of the game I used the rifle in the village but afterwards realized that it's possible to skip it and buy the superior semi-auto version at the Castle. As for the Broken Butterfly, its power eventually surpasses the Killer7, plus it's free. The Punisher is the only free weapon that's not worth using, IMO.
That said, everybody has their preferences. I can see why some players like the Blacktail but, I, personally, am all about power and the Red9 is just great.