Wow - convoluted. Couple points:
1) Most handguns do not have easily removable firing pins. 20 minutes
of disassembly to get to the point where you can remove / disable the
firing mechanism. It's not going to be something that can be
re-enabled during a fistfight.
2) 'spiking' the barrel will cause most guns to KaBoom. Mostly not
fatal in the real world, but often painful, and always disorienting.
Superglue (TM) would be overkill; something as simple as a wooden rod
in the proper diameter to jam in the barrel would do it.
3) Firearms with rapidly changable firing mechanisms are bolt action
rifles. The character could put the bolt in sans-firing pin, and when
he gets the weapon, remove the disabled bolt and replace it with a
known working one from his pocket.
4) On another line, you could have the character fiddle with the
ammunition - load the pistol with dud rounds, then after he gets it
back, reload it.
5) Following that line of thought, he could load the pistol with dud
rounds, except for good (working) primers. A primer without gunpowder
has enough force to push the bullet into the barrel, but not expel the
bullet. Then, that would create the barrel obstruction that causes
the fatal KaBoom when the real ammunition is fired. (Hoist on his own
petard, as it were).
I'm guessing that you are referring to a Colt Revolver in a heavy
caliber, like .357 magnum or .44 magnum. I have not found a pointer
to a Cobra Elite revolver. Just in case, tho, here is reference info
on the Colt automatic pistols:
Colt 1911 Auto Pistol manual:
You can see that this typical semi-auto pistol has, well, a lot of
parts. Parts 9 and 10 are the firing pin and spring, which is hit by
the hammer, part 13. Lots of parts between the trigger and hammer.
The Colt Python revolver should be close to your Cobra Elite; they are
both similar revolvers.
Colt Python Parts diagram:
Again, you can see there are a heap of small parts between the trigger
and hammer. The hammer does not have a firing pin on it, it acutally
hits a captive pin in the back of the gun. Removal of the pin will
take some time.
I'd suggest a post to the Usenet Newsgroup, rec.guns with your
questions; there are many, many experts on that group, and you will
get some quality opinions and suggestions.
I hope this helps!
colt python disassembly
pistol disassembly diagram