.30-06 can be had for less than a buck a pop, no pun intended. Okay, maybe it was.
Russians used .25 Cal Mauser Pistols to murder 100,000 Polish Officers and others
Vasily Blokhin
Blokhin initially decided on an ambitious quota of 300 executions per night; and engineered an efficient system in which the prisoners were individually led to a small antechamber—which had been painted red and was known as the "Leninist room"—for a brief and cursory positive identification, before being handcuffed and led into the execution room next door. The room was specially designed with padded walls for soundproofing, a sloping concrete floor with a drain and hose, and a log wall for the prisoners to stand against. Blokhin would stand waiting behind the door in his executioner garb: a leather butcher's apron, leather hat, and shoulder-length leather gloves. Then, without a hearing, the reading of a sentence or any other formalities, each prisoner was brought in and restrained by guards while Blokhin shot him once in the base of the skull with a German Walther Model 2 .25 ACP pistol.[13][14][15] He had brought a briefcase full of his own Walther pistols, since he did not trust the reliability of the standard-issue Soviet TT-30 for the frequent, heavy use he intended. The use of a German pocket pistol, which was commonly carried by German police and intelligence agents, also provided plausible deniability of the executions if the bodies were discovered later.[16]
An estimated 30 local NKVD agents, guards and drivers were pressed into service to escort prisoners to the basement, confirm identification, then remove the bodies and hose down the blood after each execution. Although some of the executions were carried out by Senior Lieutenant of State Security Andrei Rubanov, Blokhin was the primary executioner and, true to his reputation, liked to work continuously and rapidly without interruption.[14] In keeping with NKVD policy and the overall "black" nature of the operation, the executions were conducted at night, starting at dark and continuing until just prior to dawn. The bodies were continuously loaded onto covered flat-bed trucks through a back door in the execution chamber and trucked, twice a night, to Mednoye, where Blokhin had arranged for a bulldozer and two NKVD drivers to dispose of bodies at an unfenced site. Each night, 24–25 trenches, measuring eight to 10 meters (24.3 to 32.8 feet) total, were dug to hold that night's corpses, and each trench was covered up before dawn.[17]
Blokhin and his team worked without pause for 10 hours each night, with Blokhin executing an average of one prisoner every three minutes.[3] At the end of the night, Blokhin provided vodka to all his men.[18] On 27 April 1940, Blokhin secretly received the Order of the Red Banner and a modest monthly pay premium as a reward from Joseph Stalin for his "skill and organization in the effective carrying out of special tasks".[19][20] His count of 7,000 shot in 28 days remains the most organized and protracted mass murder by a single individual on record,[3] and saw him being named the Guinness World Record holder for 'Most Prolific Executioner' in 2010.[4]