Scott you’re incorrect. Armed security have specific training and licensing requirements set by each state. They can only carry in the line of duty if they carry a state commission.
True, they do not have the powers of a PO but they are not treated like others who do not carry a state or federal commission.
As to your question? Absolutely and I’ll use an example of a situation I was involved in a few years back.
Coming home late one night from Clovis NM to Farwell, Tx I’m passed first by a car filled with what turned out to be some very bad guys doing over 100mph in the town of Texico, NM.
They forced me off of the road wrecking my truck.
Within seconds two NM State troopers and two Clovis LEO’s come by in hot pursuit.
My truck is driveable so I quickly follow so I can be a witness and hopefully get my truck repaired at their cost.
At the state line they were forced to drop the pursuit but I could continue. Two DPS troopers picked up the pursuit at the state line and about fifteen miles or so later the bad guys car became disabled in a field and they scattered.
I’ll shorten a long story here but I was able to corral two of them and cover the officers while they detained and cuffed the other four. Had it been necessary I could have provided lethal cover out to 400yds because of the rifle and spotlight I had. WIthout my being able to do so this could have gone very badly.
Even in the city you could easily have a situation where you observed a violent felony in progress well beyond typical handgun range requiring you to use a rifle at a hundred yards or more such as say a kidnapping or home invasion where they take hostages or use some of the hostages as shields to get from the home to their vehicle while attempting to flee.