I have to agree with DRail and Departed
Most service types and LEOs are trained with their service or issue weapons and little else. And what seems to me as minimal levels of training for the most part.
For instance, I was in the Marine Corps in the long ago. In advanced training, I received about two hours of 'training' with the M1911A1 pistol. Most of it was 'keep the muzzle down range' in various colorful language, the next popular subject was how hard the thing kicked and how inaccurate it was; and I think they devoted ten minutes or so to lining up the sights. Then we were directed to the firing line where the pistols were on the bench waiting for us - we didn't walk with them in our hands at all - and I think three pre-loaded magazines with five rounds each. Shoot the ammo and get off the range.
I left a M1911A1 pistol at home when I enlisted and had some idea of how to work it. I was the one eyed man in the land of the blind.
Same with the rifle. We were more seriously trained with the rifle (an M14 in my case). We were 'exposed', or 'familiarization fire' to M60 machineguns and 3.5 inch rocket launchers and LAAW rocket launchers. Very limited.
I went to the Border Patrol Academy and received some fairly serious training on shooting the issue revolver. But it was the revolver only, and only basic marksmanship training. A small amount of 'decision' shooting' on an indoor range with plastic bullets (ten minutes of practical exercise) and a night shoot. It wasn't 'bad', but it was brief. Also some explanation of and fifty or so rounds of shotgun shooting.
Same with U. S. Customs. Good basic instruction, but no depth and nothing about tactics or gunfighting. And ONLY with the issue weapon.
Most of the people with whom I worked could qualify, clean and operate (more or less safely) their issue sidearm. However, with something foreign to them - a model 94 Winchester, for instance - and a box of ammo, most would use the rifle as a club and some few would figure out how to single load it. Perhaps a minority would figure out how to load it. (The lever is pretty obvious.) But only those who knew about them from their private study would be comfortable and have any degree of confidence.
I've been a firearms enthusiast all my life. I've read many books by shooters about shooting. Many of those people had different ideas about how to do things. Some of them had specialties. Most of them have their own particular axe to grind.
I own a fair number of firearms now. I've shot all but a few antiques. And two or three times a week I see something on one of the firearms forums I've NEVER seen! And to be honest, I no longer keep up with 'new' guns. So - just for the tally book - I have my limits.
My suggestion is to research any question of firearms, ammunition or tactics and read several different 'sources'. There is more than one way to accomplish a task, and one size does not fit all.
Except for self defense, a solid hit with a big caliber beats a solid hit with a smaller caliber. Trust me, I'm an expert.