Not mil, but I do have a story that I think is applicable. I'm sorry, but it's a little long.
Probably between 8-10 years ago, we go to a guy who is cracking off rounds outside his trailer (yeah, I know) here within the city limits. We're in Oklahoma, so a lot of gunshot calls are not, and some are. Our officers approach sneaky-like (it's night), but don't know exactly where BG is. When they get withing 40-50 yards, they hear popping sounds and notice a lot of sparks and shit flying up from around their feet on the asphalt. After careful consideration, they realize they are being shot at, and not being missed by much. They get to cover/ concealment, and start trying to locate where the shots are coming from (they had a general direction). Everyone on shift goes.
One guy/girl pair approaches where they think he might be. One has a rifle, one has a shotgun loaded with buckshot (slugs in the speed-feed stock as we issued them). Behind where they think the guy might be, there is a small wooded area, backed up with an apartment complex. We train at ranges over 15-25 yards, when there is a suspect, you select-a-slug in your shotgun. It's always been that way.
So, as they're approaching, our team sees bad guy. Bad guy sees them. Bad guy is in a lightly wooded area with apartment complex behind him (bad for errant buck rounds to hit). Bad guy shoots at them with his 9mm pistol, but misses. Female goes to select a slug, which she finds difficult while ducking and trying to not get hit by the gunfire. The guy officer (Army infantry vet, DM, lots of shootings under his belt in Afghanistan, member of SWAT team), shoots at dude 10x, hitting him 3. BTW - he really screwed up out shooting percentage numbers with this, but he puts dude down. Chick was still in the middle of selecting a slug, and the whole thing happened. She was using buck because that's what we issued and trained with. She didn't shoot because she was worried about apartment complex. I think that's reasonable, and is consistent with how we train.
So, afterward, everybody was MMQB-ing the female. "I would have just shot with buckshot". "I would have selected a slug and put him down". The usual. Everyone who wasn't there could do it better, and would have. The whole incident from start to finish (when they saw each other to the time dude was shot) was just 5-6 seconds. Officers were cleared, everything seemed to be within policy and training practices, but the peanut gallery/shit-talkers were vocal on this.
So within the year, I set up a drill at the range that I made everyone do. First, I took everyone to a qual target set up in an open area, and gave them a 2-second look at it. I then immediately asked how far it was. Nobody got close (later I heard "well, we didn't have time and we were unfamiliar with the area . . . . . and I told them, "right.").
Next, I held the "Mary drill" at the range. You have a shotgun with buckshot set up to cruiser safe. You chamber a round. I give you a 5-second target exposure at I think 30-35 yards (I can't remember exactly, I'm old). You had to either select the slug and hit the target and hit it, or hit the target with all your buckshot. We have about 90 shooters. I was able to select a slug in that time and fire (this was completely cold with no warning), and 2 had all their shot stay within the target (hit it where it would bleed). The rest either missed with one or more pellets (some many more), but the vast majority just had the target edge without firing a shot. Most were in the middle of selecting a slug. The chief complaints of the drill were lack of preparation for the drill, the distance, and lack of time. I pointed out that this was exactly what Mary had faced - but while being shot at. Can't say it wasn't a realistic drill. It was exactly what she faced. Everyone shut up. BTW - the dude that selected the slug cold was out most senior firearms instructor, and used to be the range master. He is just slick with a pump-gun.
Then we repeated the drill with a gun full of slugs. Everyone hit the target. So, we started recommending those that carry shotguns just carry slugs. The over-penetration issue with slugs isn't as big a deal as you'd think (watch gel shots with LE slugs).
We issue everyone an AR15 with an aimpoint pro anyway, so over the years, the shotgun fell out of favor. By last year, 3 people were carrying shotguns. We then changed policy, and the only PD-issued long gun officers can carry on patrol are rifles. If they want to carry a shotgun, they provide it, and must qualify with it (we'll buy the ammo). Nobody carries a shotgun now, except as less lethal weapons and breaching shotguns.
BTW - the only shotguns I've heard of being issued to the military are two people I know in the Marines (one being my son). During deployments, they had breaching shotguns with little training on them. I know the Marines have some iteration of the Benelli, but I thought those were more of an MP thing. I've seen them at gates for Pendleton.