Helmet Cam footage from Ukrainian machine gunners shows the MK-19 being utilized as it was traditionally intended. I'm going to geek out in the analytics tab.
So, first and foremost, this isn't true high-angle fire, nor is it true full-defilade fire. If you're a Ukrainian Machine Gunner reading this, I want you to know that you can go higher and farther with the MK-19 than you're thinking is possible right now, but it's going to take a bit of work and a bit of practice. At the bottom of this, I'm going to link you to a resource that will help you in the training process.
In the traditional sense, the MK-19 was designed as an automatic grenade launcher that is capable of engaging targets from full-defilade. That means, the gun was designed to be a fully automatic quasi-mortar system that could engage armored targets such as the BMP from a position of complete cover. Over the years and conflicts, the role of this weapon system evolved thanks to the role of combined anti-armor teams and mobile assault platoons who would mount it to vehicles, making it a mobile platform.
Moving on past that however, I want to talk about what's happening in this video. The Ukrainians are utilizing the MK-19 in a similar fashion as the AGS-17 and AGS-30 automatic grenade launchers. While still pretty cool, this is a mistake. As much as American machine gunners might bitch about it, the MK-19 is a Ferrari, and the AGS is a Chevy Cavalier. It can do far more than you expect if proper training is applied.
So, for our Ukrainian machine gunner friends. I want you to go ahead and click through to section 12 of this document. You might need someone who is very skilled in English to help you get this into action. Once you're there, you can use the tables and techniques as described to really get a lot out of the MK-19. You're also going to want to replace the lead leg of that M3 tripod with one of the rear legs, and put three men on the weapon system. One man pulls the trigger, one man braces the weapon system with his body weight over the top of the guy pulling the trigger, and the third man feeds the ammunition to the weapon system. Discard your feed throat, you won't be needing it where you're going.
If done properly, you should end up with a MK-19 that looks like it's in a position to kill the shooter. It will look dangerous, but when you brace the weapon properly with the two man and some sandbags, it will be safe to shoot. Use the tables provided in the above document to get an approximate range and direction, and your drones can help you make the appropriate T and E manipulations to absolutely crush light armored vehicles like the BMP from a position of complete safety. A gunner's quadrant should have been provided in the standard issue equipment with the gun itself, but if it wasn't you can still improvise adapt and overcome with proper forward observing techniques.