What entailed getting assigned to a Long-range Recon Patrol during Vietnam?

I was a LRP in Viet Nam and was put in a LRP unit when I arrived in country, you could elect to go back to the line companies , but very few did after working as a team. There was a Recondo school taught by SF, that members could go to, but with most being understaffed, few got the chance. We worked in 5 man teams with a sniper attached and some of the missions were: prisoner snatches, stay behind ambushes, as well as recon and sniper missions. There was one LRRP unit attached to all Divisions, and usually one LRP unit attached to battalions. The difference in LRP and LRRP was the different missions assigned. The MOS assigned was 11F, infantry operations intel. we had no medics and each mission was usually 5 days, so we packed for that. Difference from line companies, was they were usually resupplied every three days, which we could not because of detection.

In the 199th Light Infantry Brigade it started with no LRP elements.
On 20 December 1967, the 71st Infantry Detachment (Long Range Patrol) was activated by sixty one troops chosen by General Forbes from the ranks of Company F, 51st Infantry (II Field Force Long Range Patrol) Within a month the unit was fully operational and acquainted with it's Long Binh sector.
On 15 January 1969, Lt. Robert Eason Jr. took over the 71st with an assigned priority to reorganize it into a brigade-level ranger company by the end of the month. In conformity with this schedule on 1 February Brigade commander Brigadier Gen. Frederic Davis activated Company M (Ranger), 75th Infantry.

No idea how other units built or trained LRRP in their units.

They usually volunteered. They were small scout units at the Division or Field Force level. They started in 65 and were rolled into the 75th RGR RGT in 1969. 4th ID LRRP was known as E co, 58th IN. Here is a link of the roster of that unit in Nam. I was in F co, 51st IN (Long Range Surveillance) when I joined in 2000. LRS trace their lineage to the LRRP units of Nam. I hope this helps. I have ran into a few guys there were LRRPs in Nam. They are a very small group. There is also the LRRP association. They have been able to validate people that have said they were LRRPs in Nam.



https://www.k75ranger.com/unit-roster/

Wasn't Army back then, but in the Marine Corps, Navy Corpsmen upon arrival were typically asked if any wanted to volunteer for Force Recon. In my group of around 25, four of us raised our hands and two were picked ... but I didn't raise my hand fast enough and missed out.

CPT (Join to see) Captain, here is what I found on Wikipedia.

In Vietnam

April 1968. LRPs at LZ Stud near Khe Sanh combat base, Vietnam.
In December 1965, the 1st Brigade, 101st Airborne Division, formed a LRRP platoon, and by April 1966, the 1st Infantry Division, 25th Infantry Division and each of the four Battalions of the 173rd Airborne Brigade formed LRRP units as well.[21][24] On 8 July 1966, General William Westmoreland authorized the formation of a (LRRP) unit in each infantry brigade or division in Vietnam. By 1967 formal LRRP companies were organized, most having three platoons, each with five six-man teams equipped with VHF/FM AN/PRC-25 radios. LRRP training was notoriously rigorous and team leaders were often graduates of the U.S. Army's 5th Special Forces Recondo School in Nha Trang, Vietnam.[1][25]

Tiger Force was the nickname of an infamous long-range reconnaissance patrol unit[26] of the 1st Battalion (Airborne), 327th Infantry Regiment, 1st Brigade (Separate), 101st Airborne Division, which fought in the Vietnam War, and was responsible for counterinsurgency operations against the North Vietnamese Army and Viet Cong. [27] In the course of their duty, they were found responsible for the deaths of hundreds of noncombatant civilians who were marked as “enemy KIA”. These high bodycounts were recognized and encouraged by military officials, who were unaware of or simply didn’t care about the atrocities committed by the unit, which included the abuse of POWs, the mutilation of dead soldiers and civilians, sexual abuse, destruction of property and the planting of weapons on deceased civilians. Their commander Col. Morse ordered troops to rack up a body count of 327 casualties in order to match the battalion's infantry designation, 327th; by the end of the campaign soldiers were congratulated for their 1000th kill.[28]

The platoon-sized unit, approximately 45 paratroopers, was founded by Colonel David Hackworth in November 1965 to "outguerrilla the guerrillas".[29] Tiger Force (Recon) 1/327th was a highly decorated small unit in Vietnam, and paid for its reputation with heavy casualties.[30] In October 1968, Tiger Force's parent battalion was awarded the Presidential Unit Citation by President Lyndon B. Johnson, which included a mention of Tiger Force's service at Đắk Tô in June 1966.[31]

Since satellite communications were a thing of the future, one of the most daring long-range penetration operations of the war was launched by members of Company E, 52nd Infantry (LRP) of the 1st Air Cavalry Division, against the North Vietnamese Army when they seized "Signal Hill" the name attributed to the peak of Dong Re Lao Mountain, a densely forested 4,879-foot mountain, midway in A Shau Valley, so its 1st and 3rd Brigades, who would be fighting behind a wall of mountains, could communicate with Camp Evans near the coast or with approaching aircraft.[32]

Thanks all. I’ll leverage the provided info.

It’s very plausible now in retrospect.
Additionally:
He did make SGT in 6 months
He was an infantry brigade top shot (military award plaque stating as such)
He didn’t do drugs

So I can see now he might be of interest to leadership be part of the patrols

Who made you overseer of awards veterans wear. What businesses is it of yours.
The US Army does things they don't let a lot of people know about.

So why don't you just mind your own damn business and quit worrying about others.