What cartridge is this derived/formed from? Thanks in advance. Pak

Basically derived from the 7.62 x 39 - the base of the Beowulf is the 7.62 x 39 size to fit a modified AR 15 bolthead. The rest of it is pure designer imagination.

Check these websites -

www.gunblast.com/50Beowulf.htm
www.alexanderarms.com

Beowulf was/is the leading warrior hero in the earliest recorded written narrative , dating from approx 11th century Scandanavian mythology.

Actually, the .50 Beowulf is not derived from the 7.62 x 39. It only shares its head size. The case itself is just a longer version of the .50 AE with a rebated rim to fit the 7.62 x 39 bolt face.

So perhaps it has an ancestry based on both of these cartridges . It isnt just a longer 50 AE , nor is it a blown out 7.62 x 39 , but it is a case combining features of both parent cases.

I don't think you could say it is based on the 7.62 x 39 since you could not form a 50 Beo case by starting with a 7.62 x 39 case. That's like saying that the 30-06 is based on the 45 acp since they have the same head size.