Being outgunned and needing more firepower is part of pump. But replace the idea in you're head from "I need more firepower" to "I need better positioning" or "I need to be a better snapshooter and a smarter player"
If you have the idea you are losing because you are being outgunned, then pump may never be satisfying for you. Whether it's a T2 or a PGP pump action pistol. If you have the thought in your head that the reason for your shortcomings is that the other person has an advantage based on what they are using, that is not going to change unless you have the most up to date, expensive high end gun. You may perform a little better using an open class high performance pump (such as a T2, or any of the CCM line) in 'brute force' style firefights, but you will still be outgunned, and still lose the majority of heads up matches if you are trying to go shot for shot with people.
I play stock class, and almost always get picked before at least 1 person with a gun that shoots faster then mine. Not because I can shoot faster, or because my gun shoots further, but because knowledge of the game, experience and playing technical and using good communication are far more important then the amount of balls you can rattle of per second when you are shooting at the chrono range.
So as someone who plays stock class, I am always out gunned, or at least equally the lowest rate of fire on the field. I only refer to the disadvantage jokingly when I get picked to a team I don't want to be on (like saying "you sure you want me man? I'm only using a pump?!?" because I want to be on the other team, never works by the way, they end up always sticking with their pick). The few disadvantages to playing pump when looked at in the most basic sense, are having to pump for each shot while others just need to pull the trigger (DUH) and for stock class (in my set-up, could vary) having to rock and cock (so taking the barrel off the target between shots) and reloading. PRETTY SHORT LIST!
So if there is only 3 disadvantages, how do they play into you losing. I admit, I am not perfect, at times I have wanted to blame my gun for my downfalls and losses and shitty days on the field. BUT! When you look back and think about the times you were eliminated, where you playing perfectly? I was down on stock class for a while, but when I thought about myself being eliminated on "bad" or off days, I could rarely, if ever think of a time where I was shot out while changing 12 grams or reloading paint. I may be able to say "well I could have got that other guy out if I didn't have to rock and cock, or if I had a little more fire power he was a goner!" But the fact that I missed, or bounced a shot, doesn't inherently mean I got eliminated. So what usually leads to my eliminations is poor snap shooting, moving wrecklessly, not playing aggressive enough and allowing the other person to lay into your bunker while another person slowly advances carefully to an angle to shoot you out of bunker you. There is always something I did wrong, along with usually the other guy not doing something wrong along the way that they were playing well.
It's usually not the gun man, it's tough to accept, and a lot of times losing in what feels like a situation where you have more skill and are losing to an "inferior opponent" who has a faster shooting gun, is usually just little mistakes that after you come down from the anger of losing you can look back and think, well what did I do to end up in a situation where that mattered?
that's all I got