I am Slovakian (on my father's side) and in WW2- the British Bren in, of course, .303 and not our 30-06) had some advantages over our BAR-- The Bren (Bruno-Enfield merged) had a 30 rd. top set box magazine (about 10:30 on the clock position) which meant the operator could get closer to the ground (deck) when firing from the prone position- and unlike the BAR with the two-fire position trigger assembly, the Bren had a better and less complicated trigger assembly and a slower cyclical fire rate- darn fine weapon, IMO.
Every magazine configuration has its advantages and disadvantages. The Japanese Nambu machine gun used a magazine arrangement much like that of the Bren. Marines found that the protruding magazine was a sure means of locating a machine gun hidden in tall grass.
Both the Johnson light machine gun and the German Fallschirmjaegergewehr (FG 42) used magazines which stuck out the side, but the weight of a full magazine could make it difficult to hold the weapon upright.
The 20 round BAR magazine does not protrude very far and creates no problem when firing using the bipod. The BAR had two cyclic rates and an experienced operator could fire single shots with it.
The main problem with the BAR is its weight, because not only did the BAR Man have to carry the 20 pound +/- gun, he had to carry a belt with 12 magazines weighing 2 1/2 pounds apiece loaded. In the Marine Corps, we used three BAR's to a squad, one for every four men, so the fire power was terrific, but at the cost of having to hump the ammunition. (The Assistant BAR Man also got to carry 12 magazines).
Traditionally, the shortest man in the four man fire team carried the BAR. I know, because it was frequently me.
