gvf,
A couple of things:
I've replaced the photo with a larger one that shows the correct edge that works on the hammer. It's hard to say what it started as, because I got my BM used with an unspecified round count. How much of that edge came from the factory versus how much is wear and tear, is uncertain.
The hammer is closer to one side of the slide (the right side) because it is offset slightly, and this is evident looking directly down on it with the slide removed.
Having said that, let me add to my response to your question,
So, why is the spring so tight on Buckmarks?
You asked "why", I earlier answered with a "how". Here's my attempt at the "why".
Consider the BM and the 1911 conversions, and let's include a popular pocket 22, the Bersa Thunder. All these 3 designs work on a blowback principle. The BM slide, compared to the 1911 conversion slide, or a BERSA Thunder slide, has less mass, which means the slide of the BM would "blow back" sooner, and faster, than other designs. In order to slow down this recoil impulse, the designer has three options: 1) a stronger recoil spring, 2) a stronger mainspring (and thus, greater hammer resistance), and 3) locating the point at which the slide pushes back on the hammer to increase the hammer's leverage.
1. Recoil spring cannot absorb the entire blowback impulse alone, otherwise it would slam the slide forward as hard as it came back, so it works in combination with the hammer,...
2. ...using the force of the recoiling slide to work against the mainspring and cock the hammer.
3. By configuring the slide rail so it contacts the hammer close to its pin or fulcrum point, the design makes it initially very difficult to push back the hammer but as it moves back the hammer gets easier and easier to push, because of the changing geometry.
By combining all three, the pistol has used the energy of the 22lr cartridge to extract, eject, cock hammer and chamber another round (or lock back in the case of the last round). As a side effect, it also becomes
initially difficult to rack the slide with the hammer down.
And that's
why, compared to other pistols, it's hard to rack the BM slide.