The Heckler & Koch P2000, P2000SK, P30, & P30 are all a part of the same family of small-bore pistols generally referred to as "P-series."
They are all polymer-framed semi-automatic pistols and share basic design and aesthetic characteristics. The P2000 and P2000SK are available in 9mm, 357 Sig, and 40 S&W; the P30 and P30L are only available in 9mm. all P-series pistols have removable backstraps that can be swapped out for different sizes to help fit your hand, and the P30s have multiple side-plates as well, offering dozens of options for size and shape of grip. Additionally, they all have an integral Picatinny rail to mount accessories.
Starting at the small end, the P2000SK is a sub-compact available in two different trigger groups, SA/DA and "LEM/DAO". The SA/DA has no external safety, and is intended to be carried hammer down (decocking lever is located on the back of the pistol, next to the hammer). the first trigger-pull is a longer/heavier double-action pull and then all follow-up shots would be taken single-action.
the P2000 is available in the same configurations, and has an additional 2-3 round capacity in the magazines. As a standard "compact." it is overall just a bit bigger than the SK and I find it to have the best overall feel of the P-series pistols.
The P30 is a service pistol designed with the military in mind. the grip is much rougher and not particularly friendly for on-body carry. The P30 is a full-sized pistol, yet again one step larger than the P2000. The P30L is identical to the P30 on the back-half. It simply has an extra ~.5" of length on the slide and barrel.
I have a P2000SK in 9mm (pictured below soon), and this is my first centerfire pistol. It is exceptionally accurate (even though I'm not!) and has fed everything I can give it reliably and without a glitch. I do wish I had bought the P2000 simply because I feel it is easier to shoot and would still have been very concealable.
(That's all for now, I will update with pictures and additional information later tonight.
