I got the Silver Bullet and BB at the same time (couldn't decide which to get for my first mod, so got both. Hey, you always need a backup, right?
I would have been perfectly satisfied vaping along at 3.7v courtesy of AW 18650 batteries with my assortment of carto tanks. But I happened to visit the AltSmoke store in Columbus, and spent a couple of hours talking vape talk and testing juices, when the owner asked to see my SB. I had my favorite juice, Virgin Vapors' Kona Velvet Milkshake, in my tank. He gave it back to me and said, "Here, try this."
Hmmm. Warmer and more volumous vapor and seemingly stronger throat hit. I believe I actually can taste notes in the juice that I hadn't noticed before. He had put the familiar generic-looking green 4.9v Nimh battery in there for me to experience 5v vaping for the first time. Then he let me try his own Kicked SB. I don't recall what voltage he had it set for, but he was vaping Cinnamon flavor in that sucker. Don't know if it was the juice or the wattage, but it was way too much for me. But this did set things in motion for me.
I got a couple of the Nimh batteries and the dedicated charger for them. They were nice, but battery charge understandably is short in these, and after a couple of weeks I was noticing less and less battery charge between recharges. This wasn't the answer.
I could have gotten a Kick and an extension sleeve. I'm all about easy. That's why I have tanks, with their own juices, easy to change flavors. I figured with that many different flavors and my enjoyment of variety, I'm not going to like to change voltages with the Kick with the need to remove the battery and the device and use a screwdriver to blindly adjust the voltage up or down. Instead of an add on, I felt a true variable voltage device better suited my vaping style.
The reason I went into all of the above, before I got so long winded in my story, was to point out that you have a couple of options to try higher voltage vaping on the SB, IF that is something you wish to try. With either the 5v batteries (satisfying but frustrating because of poor battery life, not economical in the long run) or getting a Kick and sleeve extension (can also be frustrating if you change voltage frequently). Or, if you don't do either, you'll never experience higher voltage and never know what you might be missing. Ignorance is bliss.
PS: Never consider stacking batteries in your SB. Not only is trying this a realistic danger, it will void your warranty should something go 'bang'! I've seen first hand what a runaway battery can do. There's a good reason why the warnings about stacking batteries and using unprotected (or non-safe chemistry) batteries are boldly in red print on the website.