I found a very old fired inert round in the ground! It is 37mm x 107.5mm, 1.58lb. From my little research, I believe it might be from an M4? Possibly a U.S. 37mm AP-T M80 (armor piercing with tracer).
With that profile it is an APCBC that is missing the thin cap cover.
I got caught buying one of these years ago. I could see traces of solder where the cap was fixed.
Your ground dug example looks the same.
A 37mm acpbc? What gun fired that? This projectile only weighs 1.58lb (.717kg)
It is called 37mmAPC M51B1 or M51B2. It has a wind shield that is missing from your projectile.
Used in AT gun M3A1 and Tank guns M5A1 & M6.
The only other possibility is the AP M80 projectile from the M4 Aircraft gun.
I should leave this reply to the USA collectors.
Thanks for the reply. I looked up the M51 shot and that does look the same. The M51 is .87kg and the M80 is .75kg. From the amount of decay, I am inclined to think M80 still unless the M51 is the same as the M80 but with added shield. If so then maybe I’ll never know. The added mass and length from M80 to M51 looks like that’s plausible.
That is excellent references bdgreen. thanks.
I show the line drawing from the M51 projectiles.
If the cap with ballistic cap is unsoldered it looks similar to the M80AP projectile and has been passed off to collectors as an M80. I no longer have one so cannot measure the overall length and I have never found a true M80 AP projectile.
My guess now is an M80 for your query.
It could also easily be a US 37x223r M74 AP-T. They are just M51 bodies with no cap or windshield. I don’t have a manual or technical drawing but I have this photo.
Bulletpicker and the pervious posted material are showing the M74 AP-T projectile as a bit longer and heavier than this one.
The M74 is longer than an M80 or M51 body.
I think there was about 5-10mm or more difference between an M80 and de-capped M51?
It was 25 years ago so I forget the difference and did not write the lengths down.
Nice cartridge and thanks for your imput.