Bluewave 707 and Boeing757/767, i would like to comment on what you have posted here. before i do, let me just say i am pleased that this is the first time i have read a gun-in-the-cockpit thread where it has not been a gun rights debate. this has nothing to do with an american's right to bear arms, and i am relieved we are finally talking about it in its proper context.
Boeing 757/767: you are absolutely right, reinforced cockpit doors are all that should be necessary. if the door is not opened by the cockpit crew, then a terrorist cannot get in. and, as these doors are to be bulletproof and reinforced, if a terrorist is going to gain access, it will be by a means that will jeopardize the entire aircraft (read explosive). however, i do not object to equipping the cockpit crew with a final line of defense.
Bluewave 707: you're correct about the ammo, but it is has not been tested on a cockpit window at 30,000 feet. this makes me a bit apprehensive. now, i have grown up around guns my entire life, and certainly respect the many protections they afford. however, i also know how difficult aiming a firearm can be, particularly in close quarters and at a moving target. more importantly, an adrenaline crazed terrorist is NOT going to be stopped by a single bulltet, it will take several rounds to stop the attacker. so, in the two or three square feet of open space in a cockpit, we are talking about a struggle, several gun shots (in a place you definitely do NOT want a bullet to miss), smoke from the gun, the cockpit crew deaf from the shots, and no guarrantee that the terrorist will still be stopped or that the armed pilot will have had time to retrieve, load, turn, aim, and shoot his firearm.
now, i absolutely agree that just the thought of a gun in the cockpit could be a deterrent, and let's hope it is. but, i for one find it reprehensible and inexcusable that our government has allowed such a dangerous thing to be placed in a cockpit. give the pilots clubs, bats, blow darts, tasers. teach them karate, kung fu, or even voodoo. heck, put some three hundred pound bouncer in every cabin, i do not care. just do not put a firearm. too much can go wrong in too little time with a weapon whose effectiveness is based on an explosion that sends a projectile hurling at anything in its path.