from working on my eagle's trigger and the [worthless for gunsmithing] owners' manual, I have to agree: the firing pin WILL move if hit UNLESS the safety is on. The hammer, in the half-cocked position, is not safe, but neither is the hammer on a 1911 in the cocked positions unless the safety is locked [according to all of the manufacturers].
Can you do what you want? Yeah, you can. BUT, if there is a slip, the hammer will fall on the firing pin, which will move forward and strike the primer of the bullet in the pipe. Will this be strong enough to cause an AD, or will you get lucky and not blow a hole in some part of you're anatomy? Can't say.
It can be done, but not with a margin of safety I am comfortable will. I am sure that Mag Research will say "DON'T DO IT!", but they are also VERY lawsuit conscious. We can do about anything we want, if we are willing to accept responsibility for the risks involved, and the half-cocked position is not a low-risk option. Good luck and may you never have an A.D.
jms
ADDITION:
I know that using the sear is like the basic trigger function of a rifle: the pin won't move unless the sear is disengaged. However, when I carry a rifle the barrel tip is not strapped to part of my body, pointed 'south' . When I was taught to hunt, I was taught [for better or worse, this is NOT a safety lesson, but a way of understanding my concerns with the sear as the only safety feature] to carry the rifle loaded, and when the trail got 'hot' to chamber a round, when I could see the target and I was ready to fire, to disengage my safety-aim-fire. My grandpa, grandma, mom and dad all [yes, they all taught me at different times] drilled it into my head to never move through the forest with a rifle that has a chambered round and the safety off: sears CAN slip, and you can't predict that. This is the reason I am so uncomfortable with relying only upon the sear as a safety. I just can't shake the ghosts of my past. Mechanically, the sear should work fine.
