The purpose of the article is to describe the limits of phonetic variance within consonant groups listed in the article’s title and evidenced in Polish letters from the years 1525−1550, additionally taking into account the degree of standardization of individual variants, and also their chronological, phonetic, lexical, geographic and textual (idiolectic) conditioning. It stems from the presented analysis that within the discussed questions, the textual norm of the letters has a rather conservative character, which is corroborated by sole occurrence of traditional forms in the group of norm-creating variants. Despite this, the Polish language of the letters is characterised by significant openness – owing to a considerable share of innovative forms in the group of variants remaining outside the norm, although the majority of the analysed phonetic representations (13 forms) are the variants which were not accepted in the future by usage and the norm; some of them are the forms with limited, often dialectal (and even slang) scope. It must be also noted that within the analysed consonant groups, the Polish language used in the letters represents the situation basically identical with the situation presented in the printed texts from that period. There is just one significant difference concerning the simplification of the group (-)xv- ≥ (-)f-, with quite numerous evidence in the discussed letters (44%), and unrecorded in the studies on the Polish language of the printed material of the first half of the 16th century.