When I use a firearm for a specific task, I want every single piece of the weapon, and ammo to be of the utmost excellence, and conform to all tolerances and standards. If my charge is overweight or underweight, if my casing is weak or suffering from internal duress, if the bullet is not seated and crimped ... if the timing of the action is off, if any or the springs or lockwork don't integrate well with the other pieces ... if the sights and the barrel are not aligned ... then it will not function which will result in various results: blow up in my face, or fail to fire in which case my life may be on the line, or fire inaccurately resulting in needless suffering if I'm hunting, or simply miss the mark.
Now I have used some pretty amazing optics in my life, which are nearly worthless unless mounted on a weapon. I have a small cache of premium ammunition that serve no purpose in the darkness of my ammo can. I also enjoy quality firearms, but without optics and ammo they are simply toys. However, when I put all of them together, when each one of them is performing to their highest level of excellence in concert with everything else and conforming to the standards required (like SAAMI for example, or any of the metallurgical standards ...) amazing things happen.
I have found that in my decades of service, the military has brought out more excellence in me than any private sector job I've had including management, and allowed me to work in concert with other excellent folks. All of us have had to conform to standards, some of which were more visibly necessary than others, but the result is the world's finest fighting force.
My only concern in mandatory service would be that it is akin to putting random ammo or substandard parts into my fine firearm and expecting good results. There will always be those who will not or cannot work on a team, and they need to stay out. I would sooner have a homosexual operating at high standards of excellence for his/her particular specialty who knows when to keep their sexuality to themselves, than a flaming heterosexual who wants to do things their way and isn't strong enough to handle standards or orders.