Deleted member 1487
Well, the USMC is doing it again:a weapon who only has 20 rounds and is longer to reload than others isn't a great LMG (or automatic weapon like you said) IMHO. But I digress.
So a modified ZB 26 could be a nice start and a start which could lead to greater collaboration between Poland and Czechoslovakia for designing and producing weapons, again a solution which leads Poland to find cost-effective solutions for its armament. Which (relatively cheap) weapons Poland could have with friendlier Czechs? Except for tanks of course (several dozens LT 34 or 35 could not hurt).
https://en.wikipedia.org/wiki/M27_Infantry_Automatic_Rifle
And the Soviets did something similar in the 1960s:
https://en.wikipedia.org/wiki/RPK
The issue is the US and everyone else pre-WW2 was using full power service rifle rounds rather than intermediate rounds, but it was the standard model; the Germans were outside of the norm with their GPMG.
Here is the French answer to the BAR:
https://en.wikipedia.org/wiki/FM_24/29_light_machine_gun
The Czech ZB-26/30 was in the same category.
The Bren gun was a modified ZB-30.
The US used the BAR. The Swedes used a modified BAR. The Belgians used a modified BAR. The Soviets used the pan-fed DP-28:
https://en.wikipedia.org/wiki/Degtyaryov_machine_gun
So yeah, you'd have to have the Poles want to use Czech arms and even test them in the first place, then decide they need that modification. Only the Germans were interested in belt fed LMGs at the time. I think magazines were considered more reliable for ammo feeding, since no one else apparently had devised as system that worked as well as the MG34/42 one (the Belgians copied it post-war for the FN MAG, while the Brits tried to belt feed the Bren gun with their own system and failed pretty spectacularly). So you'd need to get the Czechs to even want to adapt their gun to a belt feeding system, as they would have to change the production line to create a top feed belt system or help the Poles set up their own.