It's closed.
If you take the time to sit down and read the all of the entries in the book the answer is there. RAW say that weapons called "Ordnance" use the large blast marker unless it specifies otherwise. Couple this with the fact that there is no such thing as "Ordnance Blast" in the rules anywhere and it becomes even more clear.
There are two types of ordnance weapons in 40k, they are referred to as:
Ordnance - which fires a large blast marker unless it specifies otherwise (ex: the IG Tank Hunter and the Valk Hellstrike Missile) and...
Ordnance Barrage - which does whatever the hell it does.
I could get into this whole long thing about the writer of the SM and BA codex, how he literally just copy and pasted the Vindicator entry, how the fact that Ordnance implies a large blast marker, how GW's mistake was adding in the "Large Blast" thing to some entries and not others, How it's (it is) redundant and only confuses the issue, how GW writes some shitty rules, how easy it is for people to twist or attempt to twist things, how the entry on page 58 should have simply left out the word "blast" in the first place, and how it can be read one of two ways which just adds to confusion... "[ordnance blast] weapons" which don't having a heading in the rules or "ordnance [blast weapons]", but it's (it is) 6:40am, I've got to be at the store in a couple hours to run Ard Boyz Semis, and I've had ~2 hours sleep.
