The Toolcraft will be just fine...and I love BCM stuff. For a play gun, I have pretty much figured out any decent BCG is "good enough." I have been using the piss out of a cheap Melonite BCG from AIM Surplus for a few years and its been just as good as the "proper" BCGs I have.

I stopped using the O-Ring years back. I haven't taken the time to remove the ones I do have, but I dont put them in any more, and haven't had an issue as long as the 5-coil springs are used. The 5 coil Springco ought to be even betterer.