Ball Turret - Gun positioning

TheFlash · **Posted:** Wed Jun 17, 2009 3:50 pm

Have a very basic question and I'm sure someone here has the answer:

My wife bought me a ~30 Aviation DVD set from Costco and it has a lot of National Archives footage.
Included in the footage is some excellent shots of B-17s and B-24s.
When they show the ball turret on the B-17 from the front (facing the muzzles of the guns), the right .50 cal appears to be set higher up in the ball turret than the left. (Or maybe vice-versa?)
i.e. Facing into the gun muzzles, the left machine gun is set about in the middle of the turret yet the right .50 cal appears to be ~1/3 down from the top of the turret.

Does anyone know the reason the guns were staggered in their vertical placement in the turret???
[Might need to see if I can take a screen shot or two to show what I saw.]

This is the closest public image I could find:
http://browningmgs.com/AirGunnery/tech/ ... 4-1944.jpg

Maybe the images were not of a Sperry ball turret?
Some other type perhaps???

Thank you,
Mike

TonyM · **Posted:** Wed Jun 17, 2009 4:39 pm

I am looking at a book titled:

HANDBOOK of OPERATION and SERVICE INSTRUCTIONS for
RETRACTABLE LOWER BALL TURRET MODEL A-13

This book was published by the AAF in February of 1943.

I can't seem to find anything that mentions whether the guns are off set in the manner in which you describe. And the drawings and photos don't really show the off set desplacement desribed.

The instructions for bore sighting and sighting the guns with the gun sight say:

"IMPORTANT
The guns must be aligned with each other and with the sight."

The manual does point out that the guns are adjustable laterally and vertically while installed in the turret. Instructions are given for the correct alignment of the guns with the turret itself and with the gunsight (Page 53---A. Alignment of Guns with Turret and Page 54---B. Alignment of Sight with Guns). The manual instructs on how to bore sight the guns of the turret with a target down range. A Test Target template is included. Can't find anything on off set gun placement.

Still looking. I'll let you know if I can dig up the answer.

TonyM.

TheFlash · **Posted:** Wed Jun 17, 2009 4:49 pm

Thanks Tony!

I'll see if I can review the DVDs this evening and possibly post some screen shots...

Regards,
Mike

Taigh Ramey · **Posted:** Wed Jun 17, 2009 5:22 pm

The guns in the ball turret are mounted evenly in the turret. Maybe you saw a photo with the guns off at an angle away from the center line of the aircraft. The cutout for the ball turret on the B-17 has an uneven contour. Maybe you were looking at one gun close to the fuselage and one further away because of the change in contour?

There is a different plate where the gun exits the turret casting.from one side to the other on some ball turrets. This could also lead to an optical difference between the guns.

Bluedharma · **Posted:** Wed Jun 17, 2009 5:51 pm

I am not an expert... but everything I have ever read about harmonizing the ball turret is to get them lined up.

I would also love to see a screen shot.
Regards,

TheFlash · **Posted:** Wed Jun 17, 2009 6:02 pm

Everything I had previously seen looked like the guns were parallel and lined up. That's why the footage was so puzzling.
Might be an optical illusion, but I'll see what I can do about getting some screen shots...

Thanks,
Mike

Taigh Ramey · **Posted:** Wed Jun 17, 2009 6:06 pm

Here is a shot of the Ball Turret in 909 before it was lowered back to its original position:

Here is a link to some other photos of our ball turret:

http://www.twinbeech.com/sperry_ball_turret.htm

TheFlash · **Posted:** Wed Jun 17, 2009 6:16 pm

Those barrels look even to me in those pics!

Okay, now I DEFINITELY need to get some screen shots just to make certain of what I saw and it's not my eyes that are crooked...

Regards,
Mike

Forgotten Field · **Posted:** Wed Jun 17, 2009 10:07 pm

You may be looking at turrets with guns being serviced. When the M-2 .50 Caliber is serviced and pulled from a turret, the frame of the gun is left in place- the barrel is pulled to be cleaned. I suggest that when the gun guts are pulled out, the barrel jacket may be pulled back in the process (which means the whole gun trunion and plates are pulled back as well). I don't know about the position of the rest of the gun during this, but from several gunners, this is what they did as soon as they landed- pulled the barrel and guts out of the guns for cleaning.

TheFlash · **Posted:** Wed Jun 17, 2009 10:27 pm

I found one of the images in the video of the ball turret. Not THE image I was looking for, but one of the images.
It was indeed the Sperry ball turret and it was (in this image) an optical illusion that the one gun barrel was higher than the other.

I tried to do a screen capture from the video, but no matter how I tried to save it, it would save only as a black image. (Copyrighted images do that?)
It wouldn't even format correctly in MS Paint for me to print it out and then scan it...

Suffice to say - looks like it was an optical illusion due to the position of the turret and the angle of the camera.

BUT, I will still continue my search for the ever-elusive 'multi-level gunned ball turret'!

Regards,
Mike

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Ball Turret - Gun positioning

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