Just did a search for "blackletter" on myfonts.com, should be some here that are close:
http://www.myfonts.com/search?search%5Btext%5D=blackletter&page=1

If you'll notice the 'o' and its to serif's/decorative strokes, on only the right side, the 'h' and its point reaching beyond the bottom line, aswell as the single storey 'a', it's obvious that more than half those fonts arnt similiar.

Also those two dots above the 'o', this is seriously hard..

More particularly, you could search for 'fraktur' and 'textura' as these are the historical models for the majority of heavy metal lettering (why is that?). The mötorhead logo has been extensively worked over, however, particularly in the way the m h and d angle away below the baseline, and quite possibly the h and the a have been borrowed from some other font altogether, so you won't be able to match it exactly with anything straight off the shelf.

Why not use Adobe Ironwood instead? Or, if you can find it, Cloister Black? Or go mangle up your own setting of Monotype Old English Text?

It's for a Type ID Index I'm working on for a university assignment, not for personal use. But thankyou anyway, hopefully I can find another record cover somewhere with a more distinctive blackletter typeface, as it's the last thing I need to cross off my list!

100% custom

Agreed. Ohwell, back to the drawing board..

If you only need the logo itself in vectors, here it is...

http://web.brandsoftheworld.com/search/?action=search&text=motorhead

http://typophile.com/node/20336

Don't select AC/DC
Tim