Only a few years ago, the Buzz Bee Big Blast was the blaster to mod for the NIC. It got excellent ranges and was extremely easy to mod, assuming you dealt with its weak trigger. They were cheap and plentiful and everyone had one.
Then a guy by the name of Broken_SVT took the 4B a step further. You see, if the 4B had a flaw, it was that it was a little too powerful. The problem was that if someone wanted to replace the pump, they effectively had to plug the tank, which would make it reach unsafe pressures. This resulted in a lot of controversy over the use of 4Bs as well as a lot of broken triggers. Plugged 4Bs were generally considered to be too dangerous to be war legal, but the stock pump left much to be desired.
Broken_SVT however developed a method that allowed the pump to be replaced without removing the critical component of an over pressure release valve. His method was incredibly simple and effective, and it changed the way 4Bs could be used in a war. The pressure could even be tweaked to account for the range loss in the new RSCB and hopper systems.
Unfortunately, Broken_SVT eventually faded out of the Nerf scene along with his beloved 4B. He took with him most of the knowledge and skill to create one of his legendaary blasters, and at the present, there are few who still follow his methods.
I am proud to say that I am one of the few. A SVT_4B is a blaster that is still unmatched in terms of power and range in today's NIC. If done correctly, they are one of the most enjoyable blasters to play with, and today, I will share mine with you.
Having never done the mod on an old-style 4B before, I can say that Broken_SVT had it down to an art. Every single piece fits together perfectly. With the exception of the pump, this 4B is an exact replica of his MK II write-up. The front bushing is particularly ingenious; it supports the barrel perfectly and ensures that it is 100% level.
The 4B shell is also one of the most comfortable shells available, and without the stock pump to get in the way it shoulders comfortably. The natural way your face lies on the barrel ensures that you are looking straight down the barrel, making aiming a breeze. The replaced pump also provides a convenient and comfortable grip, ensuring that you are always ready to re-prime the blaster.
Included below is a link to Broken_SVT's original write-up. There is nothing to improve upon for his methods; it is perfection.