PDA

View Full Version : Ammo loadouts for bombers



b2spirita
07-26-2008, 04:37 PM
Does anyone know how much ammo a typical WW2 heavy bomber carried, for use with the defensive guns? I was reading an old copy of the Dambusters by Paul Brickhill, stating that a 617 Sqn lanc carried 93,000 rounds. Was this representative of a bomber of the time?

berg417448
07-26-2008, 05:47 PM
I've read that B-17G's usually carried a little over 6,000 rounds of .50 caliber ammo.

Zeus-cat
07-26-2008, 06:16 PM
I went to see a B-17 that was flown into a local airport for static display or a few days. One of the men with the bomber said that the waist guns and turret guns each had 500 rounds and the ball turret had 400 rounds per gun. That would be about in the neighborhood of 6,000 rounds as berg417448 said.

93,000 rounds seems way too high. A .50 cal round probaly weighs about 1/2 pound. That would be almost 42,000 pounds of MG ammo in your Lancaster. I don't think so.

PanzerAce
07-26-2008, 07:22 PM
Originally posted by Zeus-cat:
I went to see a B-17 that was flown into a local airport for static display or a few days. One of the men with the bomber said that the waist guns and turret guns each had 500 rounds and the ball turret had 400 rounds per gun. That would be about in the neighborhood of 6,000 rounds as berg417448 said.

93,000 rounds seems way too high. A .50 cal round probaly weighs about 1/2 pound. That would be almost 42,000 pounds of MG ammo in your Lancaster. I don't think so.

There are a few problems with your analysis:

First, the 500 and 400 round counts are most likely the immediate linked ammo that is attached to the gun. In all likelyhood they carried extra belts of 50BMG onto the plane with them.

Also, AFAIK, the lancaster used .303 rounds, NOT .50BMG rounds. They are going to be significantly lighter (I'm pretty sure that a complete .303 round doesn't even come close to the weight of just the .50BMG projectile).

Also, while I don't have the exact number in front of me, I'm doubtful that a BMG round is going to weigh a 1/2lb.

Going off of a 7.62x54 round, the average weight of each round is ~430gr, counting the tins that the ammo comes in. So call it 400-420gr per loaded round. Of this, 148gr is the projectile itself, which means the case + powder + primer is going to be 1.7x the weight of the round (obivously, this can change for a given projectile weight, but its a starting point). If you take a heavy 2x bullet weight for case and powder weight (length of case vs. width of case, etc, means that a .50 is probably going to be closer to this number than 1.7), a loaded BMG projectile is going to weight about 3 (bullet + 2x bullet for the case/powder) times....call it 650gr. This comes out to ~1950gr for each projectile. Call it 2000gr even for the math to be easy, and that means that a loaded .50BMG round should be around 2/7ths of a lb each (since 7000gr (grains) = 1lb.).


Note, All of the above is guesswork, but I'm willing to be it is decently close to the final number.


that being said, 93,000 rounds of .50BMG should weigh about 13.25 tons....so they probably don't carry that much.


Ok, my roomate found it, a mil-spec .50BMG weighs 1813gr**. so 93k rounds would be just over 12 tons.

In .303 Brit, 93 thousand rounds probably makes sense. It weighs about a quarter or a fifth as much, so 93k rounds would only be 2.5-3 tons. On an unescorted mission, the pilots and crew would probably be willing to accept the 2.5-3ton weight penalty, since it means they could rock and roll whenever they needed to without worrying about ammo.



**According to DoD publication TM43-0001-27

berg417448
07-26-2008, 07:32 PM
According to this Lancaster's rear 4-gun turret carried 10,000 rounds of .303 ammunition:

http://www.lancastermuseum.ca/airgunners3.html


I also found this:



2 × 7.7 mm (0.303 in) Browning Mk II trainable forward-firing machine-guns in the power-operated Frazer-Nash F.N.5A nose turret with 1,000 rounds per gun using a Barr & Stroud G Mk III reflector sight.

*

2 × 7.7 mm (0.303 in) Browning Mk II trainable machine-guns in the power-operated Frazer-Nash F.N.50 (Boulton-Paul) dorsal turret with 1,000 rounds per gun using a Barr & Stroud G Mk IIIA reflector sight.

*

4 × 7.7 mm (0.303 in) Browning Mk II trainable rearward-firing machine-guns in the power-operated Frazer-Nash F.N.20A tail turret with 2,500 rounds per gun using a Barr & Stroud G Mk III reflector or Gyro Mk IIc sight.

*

2 x 7.7 mm (0.303 in) Browning Mk II trainable rearward firing machine-guns in a power-operated Frazer-Nash F.N.64 ventral turret with 500 rounds per gun using a periscopic sight. (This position did not have a dedicated gunner).

http://www.pilotfriend.com/photo_albums/timeline/ww2/Avro%20Lancaster.htm

ImMoreBetter
07-26-2008, 07:55 PM
First, the 500 and 400 round counts are most likely the immediate linked ammo that is attached to the gun. In all likelyhood they carried extra belts of 50BMG onto the plane with them.

I asked this question to a veteran, they did not carry any extra ammo, because it is very heavy. However the cheek guns had a few small ammo boxes that could be used as a back up.

Plus, the nose and a few of the other positions could not be reloaded.

Aaron_GT
07-27-2008, 09:40 AM
stating that a 617 Sqn lanc carried 93,000 rounds.

It was typically closer to 1000 to 2500 rpg as noted above which would give (absent any ventral guns) 14,000 rounds. Given that 617 aircraft often deleted the mid upper that would make 12,000 rounds. 93,000 rounds sounds very unlikely.

To me it might be a factor of about 10 out.

In reality often the planes carried only 500 rpg for front and top turrets, 1000 rpg for the rear (6000 rounds total) to cut down on weight on night missions.

93,000 rounds would be (for 617) an average of 15,000 rpg, or an average of 12.5 minutes. If most were for the rear guns then it would be even more! You'd need new guns after that.

Aaron_GT
07-27-2008, 09:50 AM
In .303 Brit, 93 thousand rounds probably makes sense. It weighs about a quarter or a fifth as much, so 93k rounds would only be 2.5-3 tons.

Typically a Lancaster would be around 60000lb on takeoff (my dad has my Lanc books so I can't check), of which about 8000lb would be bombload for Berlin. The standard max load was 14,000 rounds (about 1000 lbs). So taking the extra ammunition would mean reducing the load by about 6000 to 7000 lb or risk a serious overload. A load of 2000lb might make sense if target marking but not otherwise.

In reality, given equipmeny weight creep (e.g. h2s which made fitting the ventral armament tricky) and other nav and elint gear and the fact there was little to shoot at on a night mission weight was often saved by taking less ammunition, or even deleting the top turret (very common in Free French service)