The armoury at Brno also produced the Bren for an Irish Defence Force contract (again, an example of which can be found on this site); however, due to a misunderstanding, these were produced to an incorrect specification and rather than the MkI expected, a version more akin to that of the post Dunkirk MkI* were in fact supplied. Equally, the armoury at Brno, being located on mainland Europe, operated entirely in metric measurements as opposed to the RSAF Enfield which was operating entirely in Imperial. It has been said that during the conversion from the metric to Imperial, the Enfield 'inch' came about.
The story of the Enfield 'Inch' developed after an inaccurate reading of the metric blueprints lead to a difference in the tolerances of the engineering; thus rendering impossible the swapping of component parts between the Bren and ZB. Recently we have obtained a pouch containing spare magazines for the ZB39 (produced at Brno and often referred to as the Yugoslavian Bren, due to Yugoslavia being one of the first clients for this new design). There are some subtle differences in the production of the magazine for the ZB39 and that of the Bren; however it is interesting to note that the ZB39 magazine does in fact fit the British-produced Bren.Our collection comprises deactivated guns, so while we have been able to prove that both Brno and RSAF Enfield were actually working to the same tolerances, thus dispelling the myth of the Enfield inch, we cannot ascertain that it would be possible to cycle a round from the magazine into the Bren.
Shown at the top is a MkI Bren magazine, as produced at the RSAF Enfield and the bottom image is the Czech ZB39 magazine, as produced at Brno.