Anyone have thoughts on the real firepower differences between the magazine fed LMG like the Bren, BAR, & Chatellerault and the belt fed models like the Browning or Mg34? To put i in simple game terms, if ‘1’ represents a slow bolt action rifle & the BAR is rated at a ‘10’ where would the other LMG be valued? (scale goes beyond 10)

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Well, there are various different issues here. One of them is the length of time for which the firepower is sustained; any more than short, widely-spaced bursts and the key constraint isn't rate of fire or magazine/belt capacity, it's barrel heating.

There are three different levels of performance in dealing with barrel heating:
air-cooled fixed barrels (Chauchat, BAR, Browning M1919), air-cooled quick-change barrels (Bren, MG 34/42), and water-cooled barrels (Maxim, Vickers, Browning M1917).

With quick-change barrels, the constraint is the number of barrels available to keep switching. With water-cooled barrels, there is no constraint provided that you don't run out of water and ammunition!

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Exactly. I think the scale would have to be lengthened to 1-20 to accommodate the different permutations. For example, re quick-change barrels: the MG 34 & MG 42, with a higher cyclic ROF than the Bren, probably need more barrel changes over a given period of SF output. Those barrel changes take time though. Assuming endless ammo & barrel supplies, the Bren was an ergonomically efficient weapon. Despite its low ROF, mag & barrel changes were very easy, and normal service was resumed in seconds by a trained crew. I'd like to see figures on what the Reichsheer expected of their MG crews in this area.

Klive

Barrel change on the MG-42 only took a few seconds. It was longer on the MG-34 because it used a much more complicated manufacturing process (described as the Rolls Royce of machine guns). ROF for the pair are up to 1550rpm and 8-900rpm cyclic, respectively. The 7.92mm parabellum has a muzzle velocity of 2800fps and an energy of 3337lbs/ft. The MG-42 was regarded an efficient AA weapon due to its rate of fire, and both featured selective bursts or fully automatic settings (except for the dedicated AA MG-34/41 which preceded the MG-42, this weapon was only fully automatic).
Technically these guns are heavy machine guns which are capable of the light machine gun role.

The Browning .30" calibre was a heavy machine gun requiring a mount or tripod. It has a 4-500rpm cyclic rate of fire and a muzzle velocity of 2800fps and energy of around 2700lbs/ft. It was originally developed from a water cooled version to be used in WW1 US tanks, which never materialised. It was adopted for troop support.

The BAR was essentially an early SLR which was adapted to the LMG role. This was mostly due to the lack of any other LMG in frontal units. It has a 5-600rpm cyclic fast fire rate and 300-450rpm slow rate, with a muzzle velocity of 2650fps.

The Bren was actually developed from a Czech weapon firing 7.92mm ammunition. It's basically like the BAR with a cyclic rate of 500rpm, muzzle velocity of 2440fps and energy in the region of 2350lbs/ft.

I've also got some statistics for the French Mitrailleuse guns in 7.5mm and available in drum style (150rds) or belt magazines. The drum fed mle 31 has a fire rate of 750rpm cyclic, 2790fps muzzle velocity and 2350lbs/ft energy per bullet.


There was a tactical difference between the slower HMG and faster HMG, being that pause for barrel changes. It was put off much longer with the Browning say, but at the same time the MG-34 by comparison could do twice the damage in half the time.
In use as a LMG it makes little difference, short bursts are used and barrel changes are rarely, if ever employed.
In truth you cannot beat an MG-42 with any other machine gun made in WW2, except the MG-34 was constructed prettier (which brought its own problems).

One should remember too, at least as far as I'm aware is that the idea of "suppressing fire" and spraying like a wildcat all over a battlefield is not the way air cooled machine guns are used. You pick a target and you shoot at that target like an artillery mount: i.e. a small area of troop concentration, or a vehicle.
The idea of sustained machine gun fire is something which happens either when you're being invaded (and there are an endless supply of troop concentrations, in which case you must use overlapping support or retreat), or when you're in World War One using a Maxim and you're being charged by bayonet wielding maniacs.