So......yeah....no idea.

[Greatguns]

Wall anchor, no

WWII Nazi lead cyanide suicide butt capsule, in case of capture, insert.....maybe??

Lets try, old lead weight from a fishing net...for $200 Alex..

Aviano is in the Mountains no where near the Mediterranean or even a large lake so I don't think the lead weight is valid either.

[Loose}{Cannon]

What you have thar is a rather large tie-base cartridge.   

[Loose}{Cannon]

[Loose}{Cannon]

[Greasemonkey]

Wall anchor, no

WWII Nazi lead cyanide suicide butt capsule, in case of capture, insert.....maybe??

Lets try, old lead weight from a fishing net...for $200 Alex..

Aviano is in the Mountains no where near the Mediterranean or even a large lake so I don't think the lead weight is valid either.

Mountain goat breeding device, goat birth control?

[Phosphorus32]

Wall anchor, no

WWII Nazi lead cyanide suicide butt capsule, in case of capture, insert.....maybe??

Lets try, old lead weight from a fishing net...for $200 Alex..

Aviano is in the Mountains no where near the Mediterranean or even a large lake so I don't think the lead weight is valid either.

Mountain goat breeding device, goat birth control?

IED-IUD?   

[Loose}{Cannon]

I win.   

[Greasemonkey]

I win.   

Well, maybe...maybe not, problem is, the copper insert. Most black powder bullets of the early era were smelted and formed in hand molds. Simplicity, and no real need for the added "copper" insert when the bullet base itself could support the string, I did find an example of a .52 Sharps Gomex & Mills patented "multi-groove" bullet with an odd looking base, but, like a typical big bore blackpowder weapon, the bullet dimensions are way off, most, unlike what the OP posted, pretty much most all are fairly short and stumpy with a large diameter. The bullets used during the Civil War and earlier that used paper cartridges had the string/paper tie groove cast directly into the bullet base itself. All that was required was an alteration to the mold for the groove, no inserts, no extra materials required.

CW-bullet-carbine

There is always the slim chance, it's a custom job from back in the day, as most could possibly cast and mold their own if needed, especially if they had a caliber not found in the particular area or region they were in. Desperate times employed desperate measures.

[Loose}{Cannon]

It came from overseas.  You have a list of all those 150 year old calibers and how they were constructed?

[Greasemonkey]

It came from overseas.  You have a list of all those 150 year old calibers and how they were constructed?

Nope, do you, do you have your handy dandy pocket sized 150years of foreign black powder bullet ID. flip chart ver. 9.52 available in 22 different languages documenting it or are you just puffing out "assuming" that it is, what you say it is. 

Pulling the 'ol truth is what I say the truth is, huh...I've heard that from.....

Like I said, it may or may "NOT" be, there is always a slim chance one way, or the other, and no definitive true blue proof.    Repeat after me "I have no clue".

[Loose}{Cannon]

do you have your handy dandy pocket sized 150years of foreign black powder bullet ID. flip chart ver. 9.52 available in 22 different languages documenting it

Oh for **** sakes....thats what I'm asking you!!!

Its a gd projectile that is likely from a rear-tie type cartridge.  I never claimed to know nor did I state the exact name, caliber, and gun that shot it.  Thats your ****ing job mr.caliberman.