Heavy Bomber defensive weapons

I know little about gunsmithy so have no idea which approach would yield a lighter gun. I do know that the ammunition was initially larger that Hispano 20mm, which would have limited load-outs no matter what planes took it on; and in the end both USAAF and USN decided that developing a 20mm that had a faster rate of fire was preferable.

 

I'm not sure if you're aware of it, but the gunners on those bombers were operating defensive weapons.

Luftwaffe fighter pilots, not so much.

Good day to you, and my regards to your Granny.

 

Huh! German fighter pilots were defending their country against Allied bombers. Perhaps, we could just say "aerial gunnery" and leave it at that.

 

The Germans converted the MG151 into a 20mm, the MG151/20. This was facilitated by the original 15mm using a necked cartridge, with the casing a bit wider than 20mm, so it could accommodate a 20mm projectile.

 

It may be so, but it's not an idle question during war, because it affects the assessment of enemy losses. Am I right that you don't believe it is correct to assume that gunner bombers, because of the particular circumstances in which they operated, tended to overestimate their kills more than fighter pilots? To me it seems a reasonable assumption (even if the overestimation may not be that much greater), but providing absolute proofs would be tricky if not impossible.

What do you think about the question of up-gunning US heavy bombers? Would have it been technically feasible - and if yes, would have it be worth the trouble? It is interesting to notice that the Soviets managed to cram their 23 mm guns in the Tu-4 turrets without significantly affecting the performance of the plane. The Tu-4 was slightly slower than the B-29, but this may be in part due to the fact that they used slightly thicker aluminum sheets, resulting in 750 lbs increased weight.

 

That might have been more feasible in aircraft like the Tu-4 which used umanned remote controlled turrets. Similarly, our B-36 had remote control turrets mounting twin 20mm cannons.

 

The Germans started attacking face to face. They noticed the front was the weakest spot and less armed. And they aimed at the pilots.

 

I doubt that seriously from the Western Allied side, although it may have been true for the German side. Allied intelligence assessments of Luftwaffe strength was mostly based off of the extensive information they received from ULTRA sources, the Luftwaffe being possibly the most lax of the German services WRT signals security. Claims were routinely published and touted and were also the basis for naming aces, but I doubt anyone who was BIGOTED believed them.

No, I'm saying I don't know for sure. Its a reasonable assumption, but the actual evidence of what was claimed by whom doesn't seem to support the notion they aerial gunners in bombers really inflated their claims significantly more than did fighter pilots...at least in this instance on 14 October 1943. I'm also saying the calculation is much more complex than just - aerial gunners claimed 288 German fighters, damn they must have really been exaggerating.

As I think was already noted in this thread, up-gunning was attempted - see the YB-40 - but they simply didn't work. It may have been feasible in the B-29, but AFAIK was never really tried and the 20mm tail gun was later dropped (mostly due IIRC to its unreliability). In any case, it is doubtful that substituting a .60 caliber, .90 caliber, or 20mm weapon would have made significant difference, since the real limitation was target acquisition and accuracy rather than range or lethality. Worse, for the USAAF, Army Ordnance did not develop a suitable lightweight and reliable weapon in those calibers during the war.

 

Not denigrating their defensive prowess, just pointing out the Luftwaffe fighters aren't the topic.

It may be that one or more of those fighters shot down my grandpa's -17; I don't know. I do know they flew and fought as courageously as any other pilots, albeit in an odious cause.

 

I think at the end of the war, fighter performance started outstripping the ability of aerial cannons to provide sufficient hits through air-combat maneuvering. The problem was simplified mounting those cannons on bombers, because 1) the bomber had more payload and room for the cannons, ammo, and associated gear (analog-computer gun-training in the B-29, for instance); and 2) the bombers didn't perform the extreme maneuvers of fighters, meaning that slower-shooting cannons had more time to lay in on fighters in a straighter pursuit from the latter, so the firing solution was probably easier to get at than in a hairball.

Once the Aden, Vulcan, and other high-RoF cannons were able to be mounted on jet fighters, the pendulum swung the other way.

The balance between muzzle-velocity, rate of fire, and destructive power for fighter-mounted cannons was one the USAAF/USAF and USN worked on for some time.

 

Yes, as mentioned before, the US tried to reverse-engineer and modify the MG 151, which resulted in the .60 T17E3. By August 1944 GM had succeeded to manufacture reliable guns but there were problems with those made by the Rock Island Arsenal. It was however a very heavy weapon and the rate of fire was lower than the .50 M2. Springfield Armory Museum - Collection Record

Do you think it would have been possible to make a .60 version of the M2, and did they even try?
The fire control system on the B-29 greatly increased accuracy so a more powerful weapon with greater range may have been useful on that bomber.

 

To get more range out of a bigger round (M2 upgraded to .60cal), you will need a bigger charge in each round, necessitating an enlargement of breech, chamber, feed, stowage, etc. All but the last will have to be beefed up in order to accept the heavier forces generated in firing, too. All that means more weight, for a gun that doesn't outpunch a 20mm that's already been proven in service. I suspect the Ordnance Branch decided it simply wasn't worth the trade-offs.

 

Really?? I thought you just need to bore a bigger hole inside the barrel et voilà... I mean, I know I'm not the sharpest tool in the box, but how come you believe I'm a total imbecile as your post clearly implies?

 

I didn't mean to imply that, and you have my apologies. Believe me -- if I think someone is stupid, I will say so, directly.

That said, I don't think this is really the forum for me. Y'all enjoy your discussions, maybe our paths will cross elsewhere.

 

Ok, maybe I reacted a bit too... sharply, I should have toned down my answer a bit. I certainly wouldn't like to see you go, your posts seem interesting and pertinent.

About up-scaling a gun, I know you need to enlarge the various components. But I doubt it's so simple as to just increase everything in proportion (which means the surfaces to the square of the linear values, and the volumes - and weights - to the cube). If you do just that, a .6 version of the Ma Deuce would weight about 73% more than its 0.5 caliber counterpart (using the same materials). But is it so simple? Because of the square-cube law when you increase linear values volumes and weights grow "quicker" than surfaces. This implies different stress on the components, different pressure on the surfaces etc. Basically it's the main reason why a ant can lift 50 times its body weight while a human or similar sized animal would be crushed. Now, maybe a linear increase of 20% (that is from a 12.7 mm to a 15.2 mm caliber) is not enough to make a significant difference but I'm no engineer so I have no idea. Moreover, maybe there are other problems as well, like needing different tools or who knows... That's why I hope some expert (read Rich90 ) will add his two cents.

 

Hello everyone new guy here

I’ve always wondered how many bombers were lost from friendly fire with so many bullets whizzing around. Were the gunners fields of fire limited to where this couldn’t happen ? In the heat of combat I just can’t imagine accidents not occurring.

 

I doubt any were lost to friendly fire, as it would need to be a sustained firing to bring down a bomber, as opposed to a few stray .50 rounds. That is not to say that casualties that casualties aboard a bomber were not incurred from stray .50s.

Although, a few bombers were lost as they strayed underneath another bomber dropping it's bomb load...Which I guess could be classified as friendly fire.

The biggest threat though, in the tight formations was from collision.

 

I found an article very critical about the B-29 and particularly its remote firing defensive system, which is called a "dead end" (it seems a strange statement considering that remote-controlled turrets were subsequently adopted on the B-36)
Here’s why the B-29 could have had a higher loss rate than the B-17 and B-24 over Germany in 1943 - The Aviation Geek Club
According to the article the fire computer was of terrible quality. Moreover it says that a later upgrade enabled the turrets to be aimed by track motion, which during raids over Japan caused the system to be triggered by the opening of bomb doors, resulting in B-29 coming home with bomb bays riddled with bullets fired by other bombers. It doesn't however mention any bomber being lost that way. This information seems strange to say the least. What kind of track motion device could exist in 1945? I have never heard of such a thing anywhere else. It would be interesting if Rich could add a comment here, since he knows a lot about such technical details.