The Army Marksmanship Unit saw a need for sniper training post Vietnam and ran a sniper school until the start of the Infantry Schools Sniper School in 1987 and the National Guards Sniper School at Camp Robinson Arkansas about the same time period.
The AMU program was intended to provide a cadre of instructors for the Army, NG, Marine and Civilian LE including the SS, FBI and local Police Departments.
They put out a sniper guide for Law Enforcement which contained a recommendation for a LE Sniper Rifle. It was their believe that LE Sniping/Counter Sniping would be limited to no more the 300 yards. The average LE engagements were a lot closer then that.
Since most need for LE counter-sniper operations would be in an Urban environment, they believed that the 223 size bullet would be the better option, since it would lessen the change of over penetration, and limited range. They chose this round because, when properly sighted in at 250 yards., one could make head shots up to 300 yards without hold over/under.
The Counter Sniper Guide had a list of recommended rifles and scopes.
At the top of the list for rifles was the Remington BDL Varmint w/a fixed 6 to 8 power scope.
After providing Intent to Start a Sniper Program from both the Anchorage Police Department and the Alaska National Guard I got a slot in their Sniper School.
When I got back home, I set up a rifle as recommended, A Remington 700 BDL heavy barreled Varmint w/ a Redfield 6X Widefield Scope, sighted it in a 250 yards, using M193 55 Gr. Military Ball. It work as intended. It was easy with this rifle to set get head shots to 300 Yards.
I carried this rifle throughout the remainder of my Career with the Anchorage Police Dept. Later we did get a SWAT team, in which I did the Rifle and Sniper Training. Though I wasn't on the SWAT team (I was EOD, couldn't do both), I still carried the rifle because my shift commander said if he needed a shooter, he wanted a shooter not a call out.
Anyway both that rifle and I are long since retired. It has gone to the Prairie Dog Shooting Game.
Just recently a guy bought a 30k acer ranch south of me a bit, that is over run with prairie dogs that he wants removed before he can put is cows on it.
So I've been using the retired sniper rifle to help with that task, and being about 40 years old its still up to the task. I'm limited to =/< 55 gr. bullet, but it still makes "red mist".
This rifle is limited to Varmint size critters now, but in this state, 223s are legal for deer and antelope using 60 gr or heavier bullets. They are more the capable of handling that size animal and are quite accurate to 1000 yards using the 80-90 gr. pills.
Don't underestimate the 223 bolt gun.