Gerard,
I have the data out of Ackleys Vol 2 reloading book.
Its an 06 case shortened .030 or about 3mm if I have my metrics right and necked to 22 cal. it doesnt give the shoulder angle, other then to say it's steeper then the original case.
89 grn bullet and 59 grns of H870 powder gives 3455 fps.
I would guess thats about right. i had a 224 clark. That is a 257/6mm case necked down and blown out to a 30 degree shoulder. With 85 grn bullets it would do just about the same velocity as above.