In the latter camp Przeczek was forced to quarry granite in Gusen and Kastenhofen stone pits.

Przeczek leaned towards communism and in 1954–1960 was a member of the National Assembly of Czechoslovakia from the Communist Party.

In KL Gusen I (Mauthausen) Przeczek met other poets, Poles Konstanty Ćwierk, Mieczysław Paszkiewicz, Grzegorz Timofiejew and Zdzisław Wróblewski; and Czech Raimund Habřina.

He published his camp poems in 1946 in the poetry collection Serce na kolczastych drutach (Heart on the Barbed Wire), his experiences from the camp were published in 1948 in the book Kamienna Golgota (Stony Golgotha).

Przeczek's motive of hard labour in the concentration camp can be observed from the fragment of Z lagrowej ulicy (From the Camp Street) poem from his poetry collection Serce na kolczastych drutach (Heart on the Barbed Wire): Gustaw Przeczek died on 21 February 1974 in a hospital in Hradec Králové during a heart operation and is buried in Třinec.