In many ways the Hamden was a better bomber. But it was also never used for some of the roles the Blenheim was, like battlefield support or interdiction. In spite of it's "speed" it was seldom used in daylight where enemy single seat fighters could get to it.
While for Hampden it was a risky business to venture into airspace likely containing the enemy fighters, sending Blenheim in the same was not something prudent either. Not that I ever claimed Hampen was fast, either
Hampden started with one fixed .303 in the fuselage and a single .303 "K" gun in the dorsal and ventral positions, one "K" gun may have been mounted flexibly in the nose. The dorsal and ventral positions were doubled up but were still manually aimed and fed with 96 round drums.
The HE-111P "(of Polish campaign vintage)" may very well have had just 3 MG 15s. One in the nose, one dorsal and one out the bathtub. After the losses in the Polish campaign a fixed gun was added forward (probably of no more use if as much as the fixed gun in the wing of the Blenheim) a gun out each side along with an extra crewman for them and an occasional fixed gun in the tail cone. ALL flexible guns used 75 round drums and were manually aimed.
Late Blenheim MK IVs had 5 LMGs but only the pair in the turret were really effective.
Thank you for detailing about the defensive LMGs. Think we could agree that those were better suited to insert more courage into bomber's crew, than to serve as a viable defense. Also, Blenheim had no means to defend vs. attacks coming from lower hemisphere, nor to simultaneously defend vs. multiple attackers.
True but then the thick wing offered high lift without "trick" devices and offered volume for fuel tanks.
In mid 30s, the engineers can be excused for going for thick wing, since all that theory practice about high-lift devices was a slippery thing. Projecting a mid-40 plane, pretending that slats, or split-, Fowler- or Youngman flaps are not well within state of art, is something else, bringing out the planes that need 2 x 2450 HP to make 350 mph, or to carry one torpedo externally, on same power, or to create a trainer with said power.
Calling the simple flap, or even the slotted flap as a 'trick device' is a tad too much, the humble Hurricane was flying with flaps installed.
As for the plane's fuel tankage, we can see that Mosquito, Hornet, A-26 still can carry plenty of fuel, despite thiner wings. Plus, in a classic twin engined plane, fuselage can carry plenty of fuel. Especially in planes without a sizable bomb bay. In case the bomb bay is there, even better, since different combinations of fuel + ordnance can be put to a good use.
The Blenheim was outdated but the British, perhaps due to the engine problem, had nothing to really replace it. Look at the time the Americans were designing the B-25 and B-26 bombers (or even the B-23) the R-2600 was a working 1500-1600hp engine, in part due to 100 octane fuel. The R-2800 was coming along nicely (at least in the single stage version). The Merlin was in the MK X for bombers stage and moving to the MK XX and the Hercules was below 1400hp on 87 octane. Only high power engine really available to the British at the time was the Vulture and we know how that turned out. Perhaps a Hercules powered Beaufort improved could have been schemed but with 1300-1400hp engines in 1940 how much of an improvement would it have been?
There was no bomber in 1940 with 2 x 1400 HP, in service. Most were what, like 2 x 900 up to 2 x 2 x 1100, plus Italian 3-engined jobs. So the bomber with 2 early Hercules engines, even on 87 oct fuel, would be that best in the world. Come 100 oct fuel (late 1940 for the Bomber Command?) - almost 2 x 1600 HP.
Wings with extra moving surfaces are harder to build and maintain and unless you get the British to increase allowable runway lengths you were always going to have problems with British early war designs.
Don't think we should make the hype about 'extra moving surfaces'. Hampden was equipped even with lengthy slats, nobody was complaining. What were the manufacturers to do - dump the flaps other from their designs?
Building maintaining a plane that is just a more than target practice for enemy fighters AAA was recognized even by Stalin as a faulty business.
The Blenheim could have been improved with minor (relatively) modifications. Better fit and finish and better fairing. Clip the wings just a bit. Constant speed propellers vs two pitch. Two speed supercharger vs one speed. Low drag twin turret. Crop fins on the 250lb bomb like was done on the 500lb for mosquito.
The Blenheim could carry 1320lbs of bombs, four 250lbs inside, and two racks of four 40lb bombs behind the bomb bay externally (not under wing). Not much of a stretch to put either two 500lb (which it could carry anyway) with two 250lb bombs. or perhaps 4 250lb bombs with cropped fins in the inner bomb cells and one 250lb in each outer cell?
Problem comes with lack of British production of constant speed propellers and perhaps production capacity of two speed supercharger drives. The design exists for the Pegasus so using it on the Mercury is no great stretch of design. It would be worth over 100hp for take-off even with 87 octane fuel.
Changing landing gear doors to Beaufort type might help with both streamlining (tighter fit to tires) and the engine out situation.
Some other avenues: install the Pegasus, maybe Merlin XX, or Wright Cyclone, so both take off power power at altitude is increased. Shortcomings: greater drag from Pegasus engines, Merlin XX in short supply, Cyclone is a foreign engine. Further shortcomings: the more people is reworking the Blenheim more is in production, the better planes would be delayed.