Were you in the Marines, or a different branch of the military? Oswald completed ten weeks of basic training then was transferred to an infantry training regiment for another six weeks. This was an advanced boot camp that concentrated on the basic skills of combat and amphibious techniques and methods all marines must know. After that he showed a special interest in pistol training according to his pistol instructor Sergeant Arnie Vitarbo in Japan. And according to Vitarbo, Oswald was better than average. Tippit found that out the hard way.
As I say, discussing this with forum members who were not in the army is difficult.
As for example, training urban warfare you realise that using a rifle out of a window is a nightmare, a roof top is not ideal but is much better.
I received similar time in basic training in a European Nato country but was then assigned to a combat unit and this was my daily job.
Oswald, however, was assigned to a radar unit, plenty of things to learn and carry out on a daily basis.
I'm interested in the in the trigger of the CE 139 which apparently did not have a military configuration to prevent a startling effect, but I just don't know because I have not seen it explained anywhere ...
But since this is not a matter of faith to me, I see what I see with the information I've got regardless the directions it takes ...