Yes, it sure could be a bag mould.
150 balls per pound would equal a 150 bore rifle.
So, probably not.
From the limited view of the cavity, I would guess a .32 or .36 maybe?
It looks like the sprue opening is almost as big as the ball cavity.
150 is probably a model number or some such thing.
John

Miss you old friend!

Thanks for the help and encouragement Joe. I'll never forget it.

Sadly not...

Had our first shoot of the year and had a lot of misfires and hangfires with the rainy damp weather. But certainly was good to get out and make some smoke. [ Invalid Attachment ]