Hi Renrich,
>Comis, I think you would find that a 50 BMG has a longer effective range than most 20 mms although not as destructive with a hit.
I once asked Tony Williams (author of "Rapid Fire" and the "Flying Guns" books) for the formal definition of the term "maximum effective range". To my surprise, he pointed out that it was a rather poorly defined term without a clear way to arrive at the figures you usually find quoted under this headline.
This has some relevance to the question of comparable effective ranges as we have to establish what it is what we'd like to compare
I believe that the mention of "effectivness" in the term is decisive for a definition. It's not "efficiency", which would mean we'd have to compare effort spent to results achieved, but plain effect - results achieved regardless of the means.
If I'd make an attempt at a definition, it would be something like:
"Maximum effective range is the range at which a battery of guns, spending the full amount of ammunition that it has available, has a chance of destroying its target with a certain probability in an engagement of a certain duration."
The probability mentioned in that definition should be comparatively low so that a target beyond maximum effective range could feel fairly safe from destruction - one might say 1% for example. (It's assumed that destructiveness decreases with increasing range.)
This definition is interesting because it leads to a number of unusual conclusions:
- Maximum effective range depends on
... the number of barrels installed,
... the amount of ammunition carried,
... the destructive power of the round,
... the durability of the target,
... the duration of the engagement.
Of course, it also depends on the "traditional" characteristics of a gun, such as hit probability at the range in question, but the unusual aspect is that maximum effective range is not a property of the gun alone, but rather one of the entire weapons system. For example, if one has already used up half of one's original ammunition supply, the maximum effective range drops for the rest of the mission.
I think this definition can be used to explain why a rear gunner can feel out-ranged by attacking fighters even if his rearward-firing 12.7 mm machine gun has a much flatter trajectory than the fighter's forward firing 20 mm cannon.
(It can also be used to explain how Sorley arrived at the conclusion that the RAF fighters would need an eight-gun battery
By the way, the Luftwaffe often used cannon in forward firing positions even when the rear guns were rifle-calibre only because combat experience showed that these guns would have only very short periods during which they could engage the enemy. The greater effect from cannon shells was more important than the added weight of the gun - this could be compensated by supplying it with a smaller number of (heavier) rounds.
I figure the idea behind the B-17 nose cannon was similar!
Regards,
Henning (HoHun)