B-17, B-24, or Lancaster

[Nonskimmer]

the reason you've never heard of the Mk.XII is because it doesn't exist maybe you're thinking of the Mk.XII hurricane which i believe Canada produced.

Correct. Canada produced the Hurricane Mk.X through Mk.XIIA, with the exception of an initial batch of Mk.I's. All Canadian built Lancasters however were designated the Mk.X (redesignated Mk.10 post-war), regardless of any minor modifications made.

Sorry, I hadn't even picked up on that.

 

[k9kiwi]

My apologies.

Note to self....

Stop mixing programing, alcohol, and forums.

Even the program didn't work today, took two hours to sort the mess I made.

However the Beer did.

 

[Nonskimmer]

All was not lost then!

 

[daishi12]

now then, if someone could tell me the weight of a .50cal round or even better the weight of say 100 plus links, i can post more about this little turret debate.........

I have found 1 site which states that the total weight of a single .50 BMG round is approx 1760 grains or approx 4 ounces.

Assuming that the Lanc is up gunned to 8 .50 M2's (nose, mid-upper, mid-lower, tail with 2 guns each) each gun having approx 3 minutes firing time per gun - given that the M2 has a rate of fire of 550 rpm this amounts to 13200 rounds of ammo = 3300lb (approx 1500Kg). This does not include the weight of the ammo belts.

I cannot find a comparable weight of the .30 cal round so I am having to make some big assumptions - I think it would be resonable to assume that the .30 cal round would be about 1.3 ounces which gives the following figures - Browning 1919 @ 600 rpm for 3 mins = 14400 round = 1170lb (approx 530Kg). This does not include the weight of the ammo belts.


The additional weight of crew (gunner + co-pilot) plus turret redesign plus the guns themselves the weight could be about 770lb

So total weight could be in excess of 4000lb extra.

Taking into account Eagles comment about not fitting M2's to the UH60 because it causes cracks in the airframe, this would be amplified quite significantly firing eight at the same time.

I think that if the above thoughts are taken into account, then my earlier thought that if the Lanc was converted to daylight tactics it would become mediocre (fuel/bombload) has an amount of validity.

If, however, there had been a number of B17's given to the RAF for night time duty it would make an interesting discussion, i.e. down grade the guns to .30 cals, lose the waist gunners, and use the weight savings to increase bomb/fuel load.

 

[syscom3]

.....If, however, there had been a number of B17's given to the RAF for night time duty it would make an interesting discussion, i.e. down grade the guns to .30 cals, lose the waist gunners, and use the weight savings to increase bomb/fuel load.

I would keep the .50's, but convert the ball turret to a tunnel gun setup, remove the waist guns, remove the radio operators gun, perhaps use only a single .50 in the nose instead of the turret on the "G" model.

You could even reduce the ammount of ammo per gun.

However that weight savings would be offset by the need for more avionics to successfully operate at night.

The same holds true for the B24.

 

[daishi12]

I would keep the .50's, but convert the ball turret to a tunnel gun setup, remove the waist guns, remove the radio operators gun, perhaps use only a single .50 in the nose instead of the turret on the "G" model.

You could even reduce the ammount of ammo per gun.

However that weight savings would be offset by the need for more avionics to successfully operate at night.

The same holds true for the B24.

I would convert the .50's to .30's , but with possibly quad .30's in the ball turret and tail, strip out the waist guns, have about 3-4 mins of ammo per gun (I don't know how much ammo was carried for daylight missions) and have the same radar that was in the Lancs.

The weight lose and smoother airframe (no huge holes in the waist) would have significant impact (faster, higher, handles better), even with the weight of the improved avionics taken into account.

 

[k9kiwi]

Stop cunfusing the British .303 round with the American .30 they are different beasts

British Browning .303

Caliber 7.7 x 56 mm Rimmed
Weight 10.6 Gram
RPM 1150
Muzzle velocity 750 M/s
Gun Weight 10 kg

American Browning .30

Caliber 7.52 x 63 mm
Weight 10.5 Gram
RPM 1200
Muzzle velocity 870 M/s
Gun Weight 10.3 kg

American Browning .50 M2

Caliber 12.7 x 99 mm
Weight 43.3 Gram
RPM 750-850
Muzzle velocity 880 M/s
Gun Weight 29 kg

 

[Glider]

Similar to Syscom I would ditch the chin turret, waist guns, radio op gun but would keep the ball turret, remember that most nightfighters came from below.

 

[k9kiwi]

have a look at Kiwi Aircraft Images it shows the Lancaster I regularly visit at MOTAT Auckland NZ.

Go to the features pages and look at the Lancaster pages, it shows the .50 Rose Rice rear turret and near the bottom can be seen a few features of the ammunition and feed mechanisim.

Note in the two pics below the difference from 2 tracks per side (.303) to one track (.50).

Also note the intermediary feed motors required to overcome inertia of the belts.

 

[k9kiwi]

Must stop multiple posts, I finally found the Advanced Edit Button, Doh. I found this for Lanc.

From left to right.
.303 British (7.7x56R)
.5 inch Vickers (12.7x81)
.50 Browning (12.7x99)
20mm Hispano (20x110)
7.92mm v-Munition (7.92x57)
20mm MG-FFM (20x80RB)
15mm MG 151 (15x96)
20mm MG 151/20 (20x82)
13mm MG 131 (13x64B)

 

[daishi12]

Stop cunfusing the British .303 round with the American .30 they are different beasts

Hi Kiwi, all we are trying to find is the comparative sizes of the complete cartridge i.e. case, propellant and bullet. I have found 1 source that states that the .50 weighs in at a touch over 4 oz and is 99mm in length..do you have any info on either the .303 or the .30?

 

[the lancaster kicks ass]

now i have the baisic figure of 1x .50cal= 4 ounces i will post at greater length tomorrow morning about the weights involved with the extra guns/ammo using more official RAF figures, i'll have to make some estimates as to the weight of the links

 

[Jank]

I would be surprised if a loaded .50 BMG weighed in at 4 oz. or more. Even a 750grain projectile weighs 1.71 oz. (One ounce equals 437.5 grains)

I don't think the case, primer and propellent weigh as much as the projectile.

I have a loaded .50 BMG cartridge at home but no scale for measurement in ounces.

Here is a link that indicates that a .50 API cartridge weighs in at 4.032 oz. with a 622.5 grain projectile (1.42 oz.). I find it difficult to believe that the case, propellent and primer would be so heavy but perhaps I am wrong.

.50 Caliber Browning (12.7 x 99 mm) Ammunition

 

[k9kiwi]

All you never needed to know about the .50 cal round

.50 Caliber Browning (12.7 x 99 mm) Ammunition

Note the list for M2 Ball states 1,813 gr (117.48 gm)

now 117.48 grams converts to 4.143943 Standard Ounces and 3.776888 Troy ounces.


yet MILITARY AMMO -- .50 CALIBER

Shows from the Army Ammunition Data Sheet that it is a 709 gr round at 3050 fps

Still Heres what Lanc was after from this page

The weight of 100 rounds of linked M2 ball in ammunition can is approximately 35 pounds.

I guess it depends on where you get the data from.

Take your pick.

 

[Jank]

Great link there k9kiwi. How'd you ever come across that?

 

[k9kiwi]

Um. My other job is programming internet security systems and web network structures, online databases etc. Lots of 1's and 0's in a row.

Not hard to search stuff when you get it worked out how the puppy works.

My other job is playing with water and fire, but thats the fun side.

 

[Jank]

I was half joking k9kiwi.

I cited the .50 Caliber Browning (12.7 x 99 mm) Ammunition link in the post right before yours.

 

[the lancaster kicks ass]

thanks for that added info, i realize they're not British/RAF figures but it's all I've got so bear with me........

the original question posed i believe was did the ammunition and guns carried by the .50cal rear turrets incour greater weight upon the lanc than the FN.20/120 series ammunition guns? I'll probably pass comment on the actual turrets as we go

so, standard ammo count for lanc's rear turret= 2,500 rpg, 10,000x .303 rounds in total for the rear turret, now including links and fixed ammo bins that's 661.5lbs

now the guns, 4x browning .303s weighed 92lbs

ammo and guns for rear turret= 753.5lbs (but bear in mind some of the official modifications to the lanc would reduce this very slightly)

and that's for 130 seconds of firing time, which even by day you'd be hard pressed to use up

OK the .50cals, the Rose Rice turret carried 335rpg and 2x .50cals, so using the rough figure 100 linked rounds= 35lbs, 35x 3.35= 117.25lbs, times that by two 'cos of the two guns= 234.5lbs of ammo carried, each .50cal weighed 64lbs, giving a ammo and gun weight of 362.5lbs, and that will give you 24 seconds of firing time, which by night is fine but by day you might want a little more, so what happens if you double the ammo count...

48 seconds of .50cal firing time plus guns= 597lbs, so even if you double the ammo count of the .50cals the all up weight is less than that of the 4x .303s, and it can be assumed the actual turret weights will be roughly similar with the Rose Rice and FN.82 and FN.20/120, the .50cal turrets will weigh more but certainly not enough to make up the 156.5lb difference, so the .50cals do offer a weight advantage........

but i believe this's in the context of daytime missions, for which you will be wanting a ventral turret no doubt? well this poses a problem... can you do without H2S in daytime is the question? because if you still want H2S the best we can do is a single .50cal or .303 sticking through the rear of the fuselage somewhere, which would at least be enough to discourage attacks from the underside, the other question is would you have an extra gunner to man the position? with the FN.64 it was the responsibility of the dorsal gunner to man the ventral gun, so let's try out a few possibilities assuming we're going on a daylight mission with a .50cal rear turret with double the ammo count and, to make things easy, no H2S

option one- a single ventral gun and no extra gunner

when carrying a single ventral gun typical load was 1,000 rounds with a .303, it would only be a few hundred with a .50cal, so we shall assume the RAF's being it's typical self and gives this lanc a .303 and 1,000 rounds- all up weight roughly 90lbs including mount and ammo bin- for such a tiny amount the bomb load would not be adjusted

option two- a single gun plus extra gunner

carrying an extra gunner was very rare but a gunner plus 'chute weighs exactly 200lbs according to the RAF figures of the day, so this option has a hefty 290lbs to it's name

option 3- FN.64 turret and no extra gunner

this option would completely dissallow the H2S system so take that into consideration. weight of turret= 122lbs, two .303s= 44lbs and the standard 750rpg= 99.5lbs giving a total weight of 265.5 lbs- that's less than the option with a single gun and gunner! but does mean no H2S and one gunner manning two turrets (which is what the RAF did when the FN.64 was carried

option 4- can you guess what it is yet? yes, FN.64 turret plus extra gunner

all up weight- 465.5lbs, and for a weight like this the payload would be reduced by 500lbs, but it's not like the lanc would miss it, but this option would again dissallow H2S, but is it needed by day?

also bear in mind as this lanc has a twin .50cal rear turret you've saved roughly 150lbs over the quad .303 turrets, so if you take away 150lbs from each of the above options that will be the actual weight penalty............

and i can now see Adler and FB wondering how this will effect the centre of gravity, well i can't exactly work it out myself however i am looking at loading charts giving the moments and the lanc has travel limits of 41-60.6 inches aft of the datum point, which looking at some of the moments any of the options above will suffice, and if not there are, as in any aircraft, hundreds of other things you can adjust to get the correct loadings............

ummm, I've spent so long doing this i can't actually remember if there's anything else that was being questioned? if there is ask and you may receive........

so given those figures it's up to make up your own mind as to which you think was the best option, remembering any weight increase will cost you fuel economy........

lastly my sources- with the exception of the weight of the .50cal rounds all my figures are from actual RAF sources and would have been exactly the same figures the crews would have used to work out loadings in their aircraft so they are the gospel, however bear in mind i'm only 16 and am simply messing round with figures so it's up to you how you see the data, any input on what I've done here will be welcomed, as long as it's reasonable

 

[daishi12]

Kiwi has posted some excellent info in the Lancaster Turret thread.

 

[k9kiwi]

And full specs for the Bolton Paul .50 cal type D have been posted in it.

Of note for Lanc
Armament: Two 12.7 mm (0.5 in) Browning No.2 Mk.II guns
Ammunition: 1,515 rounds per gun

Empty: 200 kg (440 lb)
Armed: 249 kg (548 lb)
Weight of guns: 33 kg (72 1/2 lb)
Weight of ammunition: 415 kg (914 lb)

take the empty 440 lb and add 72.5 for guns = 512. lb.

the disparity between 512.5 and 548 = 35.5 pounds worth of ammunition in the rails and and feed system within the turret itself.

914 lb - 35.5 = 878.5 lb for the ammunition outside the turret.

So

548 lbs + 914 lbs + 200 Lbs (Gunner) = 1,662 lbs

Add about 50 lbs for tracking etc and about 50 lbs for the two feed motors and we are stacking up at 1,762 lbs.

The FN.20 had an all up weight including gunner of 1,370 lbs (I have tacked on an extra 20 as the figures shown in the other thread are for a 180 lb gunner)

Now we have a disparity in weight of 392 pounds.

However it must be noted I am still digging out the specs on the Rose Rice turret, as the BP was only fitted to Halifaxs' and post war Lincolns.

Also the thinking within the bosses of the RAf was that with good depression angle on the rear turret as opposed to the B-17 rear turret, even daylight attacks hardly justified a lower turret as the number of planes involved and superior range of the .50 would drive off most belly attack flight proflies.