US WWII 1943 120mm or 4.7 inch Antiaircraft Artillery High Explosive Shell M73

[M8owner]

This is up for bid on Gunbroker currently. As I have never seen one before, I am attaching the photos for your review.

 

[US-Subs]

They used to be much more frequently seen back in the 70s and through the 80s. Never exactly common, but not rare back then. The M61 fuze is unique to this round. Separate loading, it used the same large case as the 120mm tank. I don't think I've ever seen one stamped that early though.

 

[M8owner]

Thank you, Jeff. I would like to point out that I am 100% confident the 120mm tank and the AAA gun used different cases. They look very much the same, but they are not. I have had my hands on several of each.

 

[charley777]

Interesting that the cases were different.
Various sources provide the same measurements.
So it would be of value to learn about the differences.
Are you able to supply more information?
Thanks very much
Cheers

 

[US-Subs]

I'm not a big case guy, so can't say anything more to that aspect - I am certain that the powder loads and designations were different regardless. I have two of the tank (?) cases with different markings, apparently the loads were different for different projectiles. Must have made it fun in the confines of an armored vehicle, separate loading and each round with a different case. My weekend starts tomorrow, I'll try and post a couple of pictures.

 

[M8owner]

Here is another thread on this site that clearly shows the tank case in official documents.

http://www.bocn.co.uk/vbforum/threa...d-for-the-M103-Heavy-Tank?highlight=m103+tank

 

[SG500]

Here is another thread on this site that clearly shows the tank case in official documents.

http://www.bocn.co.uk/vbforum/threa...d-for-the-M103-Heavy-Tank?highlight=m103+tank

Just to confuse things, here's the British version

http://www.bocn.co.uk/vbforum/threads/39365-120mm-Conqueror-rounds?highlight=conqueror

Dave.

 

[SG500]

I also found this in my files that shows the tank rounds, not sure where it came from.

Dave.

 

[M8owner]

Thank you for the reference on the British version, Dave. The British cases are threaded or crimped at the top. You show the APDS sitting perfectly on top of the case. That is not possible with all the American projectiles; they would fall right into the case with the case mouth wider than the projectile. If I did not know any better, I would say the APDS was threaded on the case and loaded as a fixed round.

I found a 120mm case at a military show last year and opted not to buy it as I determined it was for the AAA gun. I am now searching for the documentation I referenced to make that call.

 

[Eggburt1969]

Thank you for the reference on the British version, Dave. The British cases are threaded or crimped at the top. You show the APDS sitting perfectly on top of the case. That is not possible with all the American projectiles; they would fall right into the case with the case mouth wider than the projectile. If I did not know any better, I would say the APDS was threaded on the case and loaded as a fixed round.

Going by other documentation I have, the screw in bit of the UK 120 mm cartridges is just a charge closing/sealing cap/plug.

Trying to man-handle and load a complete round if it was fixed wouldn't be easy for the average person, this as it would weigh in the order of 40.0 kg (88.2 lb) for a high explosive (HE) round and 48.7 kg (107 lb) for armour-piecing ballistic-capped tracer (APBC-T) round.

As such, and as far as I can tell, both the US anti-aircraft and tank rounds, along with the UK tank rounds are all two-part loading.

Edit

For note the HE round weight is for the later lower velocity (2,500 ft/s, 762 m/s) rounds, such as the M356 (T15E3) HE-T and not the original M73 high velocity (3,100 ft/s, 945 m/s) round. A complete M73 round would weigh around 45.1 kg (99.5 lb), so about the same as a 155 mm HE projectile.

 

[M8owner]

Ok, I can confirm that I am not totally crazy. I have attached the manual image for the AAA round. It is almost exactly like the tank case. The maximum height for the case plus plug is 0.09 inches or 2.3mm shorter than the tank round. The official case numbers are M24 and M34. The case number for the tank round is the M109. However, I noted there is another option for a much shorter case for a HEAT round. US Subs provided example photos of the HEAT and short case in one thread. The challenge you encounter is that most of the cases you find have "T" numbers.

 

[SG500]

Thank you for the reference on the British version, Dave. The British cases are threaded or crimped at the top. You show the APDS sitting perfectly on top of the case. That is not possible with all the American projectiles; they would fall right into the case with the case mouth wider than the projectile. If I did not know any better, I would say the APDS was threaded on the case and loaded as a fixed round.

.

Hi, to avoid gatecrashing your Anti Aircraft thread with too much tank detail I've updated the Conqueror link with a load of photos and measurements:
http://www.bocn.co.uk/vbforum/threads/39365-120mm-Conqueror-rounds
The 135mm diameter top to the Conqueror case is closed with a bakelite/plastic cap. The APDS projectile which has a 130mm diameter rear sealing skirt on the projectile sits on it conveniently for the photograph. The other case I had didn't have that cap and yes you're right, the HESH projectile would have fallen inside.
If you look at post 8 above the differing types of caps are visible.
Having checked Hawkinson for the dimensions of the US 120mm AA and Tank and compared them to what I measured with the Conqueror case they appear to be the same dimensions.
Hope this helps.
Dave.

 

[US-Subs]

Here are my two cases for the tank gun, plus the practice AP rounds, WP, HE and a couple HEAT. In addition there is the drill round and case for the AA round, plus a page from a 1944 Ordnance magazine.

 

[M8owner]

The M73 shell with fuze sold for $600. The same seller sold an M109 tank case at the same time on GunBroker; it sold for $500. The bidding was very active for both items.