YAVORIV, Ukraine -- 30 mm rounds break the sound barrier, piercing the icy cold silence of the night. A Ukrainian BMP-2 fighting vehicle fires multiple live rounds in rapid succession.

"Hear how fast they're firing? That's what we call silly," says Sgt. Brian Francis, a former cavalry scout who is now deployed to Ukraine as a team leader with Assassin Company, 1st Battalion, 179th Infantry Regiment, 45th Infantry Brigade Combat Team, Oklahoma Army National Guard.

The rate of fire may be "silly," but the training itself is deadly serious. The men who man these machines may have to use them in combat once they complete their training at the International Peacekeeping and Security Center, near Yavoriv, Ukraine.

Sgt. Ricky Mayes, a native of Duncan, Oklahoma and the master gunner for 1-179, stoically watches the live-fire training from an observation tower.

Through Joint Multinational Training Group-Ukraine, U.S. Soldiers like Francis and Mayes, along with Canadian, Polish, Lithuanian, Danish and British soldiers, have the opportunity to serve as advisors to Ukrainian combat training center staff.

When JMTG-U first began, these allied and partnered nations led rotations of Ukrainian battalions through defensive training. Now, the Ukrainian instructor cadre is well established.

Ukrainian Senior Sgt. Sergiy Senkevych is a second-year CTC instructor. Before joining the CTC staff, Senkevych served the Ukrainian army as a tank commander on the BMP-2. He began his career on the BMP-1 as a gunner and later learned NATO tactics and techniques while deployed to Iraq and Kosovo on the BRDM-2, a smaller armored infantry vehicle.

Senkevych and other experienced Ukrainian soldiers now fulfill the primary trainer role.

Their goal tonight is to ensure that the soldiers of 1st Battalion, 28th Mechanized Infantry Brigade complete their gunnery tasks safely and to standard.

"Some of the crews are better trained than others," Senkevych explains through a translator. "First, we determine their level of readiness, and then, if we see they are weak in a certain area, we retrain them. If a crew does not do well, they complete the exercise again and again until they achieve success."

While some of the men have prior experience on the BMP-2, a light infantry fighting vehicle similar in size and function to the U.S. Bradley Fighting Vehicle, many do not.

Ukrainian Senior Sgt. Vyacheslav Berechchagin, one of the tank commanders, is one of the few who has had formal training prior to his rotation through the IPSC.

"The tank commander has to be able to perform every job on the vehicle," Berechchagin says. "In the East, we learned everything on the go. Now here, we're able to take our time. We're learning to work together more as a team."

When the conflict in Eastern Ukraine began in 2014, Berechchagin was conscripted into the Ukrainian Army, but now he serves as a volunteer. He has spent the last two years fighting in the antiterrorism operation in the east of his country.

Asked if he has a family, Berechchagin laughs. "No," he says. "The machine is my baby. She never lets me down."

Another tank commander, who chose to remain unnamed, says that he too has years of experience fighting in the ATO, but only in the trenches as a foot soldier. This is his first time conducting mounted infantry training.

Because safety is paramount, the CTC instructors decide to eliminate the maneuver component of live-fire training tonight.

"Instead of worrying about 'shoot and move,' we're just concentrating on 'shoot,'" Francis says. "That way, [the new gunners] get more time on the gun without having to worry about dividing their attention between multiple tasks."

After explaining that many of the soldiers here are shooting for the first time, Senkevych says, "Bounding is a sophisticated task, so stationary live fire is as far as we're willing to go tonight."

From atop his observation deck, Mayes troubleshoots range operations.

"Of course, ideally, we'd like to stay within the American gunnery tables," he says. "But the training value of this is worth so much more than just checking that box."

He suggests that there are some minor changes the CTC staff could make to help the range run more efficiently, but overall, he's pleased.

"What I've seen has exceeded my expectations," he says. "[The CTC staff] are just incredible, salt of the earth people who are passionate about their jobs, and they're knocking training out of the park."