Sounds like you have a very nice old rifle there Hendo. Will be interesting to see how the heavy for calibre 117gr bullets go in your Vickers Mauser.

The original factory load ballistics for the 100gr bullet gave 3000fps, don't know barrel length used, but this is better than the 250 Savage which achieves around 2800fps with the 100gr bullet. The Savage only gets to 3000fps with the 85gr bullet. Should be able to get around 2700-2800fps with the 117gr bullets in the Mauser .242 which will drop animals nicely.
What do you use for cases for your .242, are they original cases or formed from something else?

You may have seen them before but FYI I have attached a scan of the ballistic tables for the "magnum small bore" cartridges from Taylor's book 'African Rifles and Cartridges'. Taylor acknowledges the tables were courtesy of Sir Gerald Burrard. Note the .242 is called the .242 Vickers in the tables, so you and 3DM are in good company calling your 'cartridges' .242 Vickers.