I found this while metal detecting in the Mullica River, NJ. It was in three feet of water, it measures 15/8 inches in length, it is 3/4 " at the base. It seems to be lead, Can someone give me some information on this object?
Shotgun slug is right I think. Looks a lot like this one:
View attachment 76612
http://www.dixieslugs.com/products.html
Cool... I think that's an updated design of them... I couldn't find an image that matched... only text description of them in a book...lol...

A bit off topic but I shot a 10 gauge once and decided that if that's what I had to do to get a bird to eat I'd just go to the grocery store. About the same time I also shot (once) a .457 Weatherby Magnum and determined that I was more than content to just let remarkably large game alone.
Years ago when I did IPSC I learned to handle a 12 (not magnum) semi-auto and it's plenty enough for me. I do wonder what was being hunted with the OP round ?
Have seen and handled the 10's.. but never had opportunity to shoot one.... Older brother liked the big guns... He had a 300 Mag... that was an anti-tank round I think... shell looked like a 12 ga shell with a 30 cal bullet stuck on the end... geez... He also had a couple Weatherbys... Very nice guns... and very nicely expensive too if I recall.... I just had my plain old 12 ga in 2 2/3 shell.... back when everyone was running to buy and brag on the 3 and 3 1/2 mag shells.... I put just as much if not more meat in the freezer as they did...lol.. They would come out with their 300 mag with scope big enough you could see a fly at a thousand yards... me with my simple open sight 30-30..... lol.... bigger isnt always better... lol
I found this while metal detecting in the Mullica River, NJ.
I'm no expert on antique shotgun slugs myself, but I am a bit of a combat shotgun expert, so hopefully some of my useless knowledge will help you.
A 12 gauge shotgun with a cylinder bore is usually .729 caliber. A 10 gauge is .77 caliber A slug for a shotgun has to fit inside the shell, and has to compensate for the reduction of barrel size in shotguns with different chokes, so they're usually smaller than the bore diameter, usually running about .69 caliber for 12 gauge slugs.
If the projectile you found is 3/4", that makes it a .75 caliber round. It's possible that it is a 10 gauge slug, as that's about the size of one. I don't think it would be a 12 gauge. It's probably very old then, just going off of my own theory that 10 gauge was more popular than 12 gauge in the mid to late 1800's, and nobody really plays around with the big 10's anymore.
Hope this helps.