This has been a very frustrating thread to try and do anything with as it won’t show the reply nor would it allow me to post information I found just keeps coming up with "Token Expired Reload the Page":mad::mad::mad::mad::mad::mad::mad:
After umpteen attempts which included a posting of the original thread which then got lost somewhere so I have resorted to starting another thread on the same damn question……

Here is my reply to 4MD;

Thanks 4MD I had to go to your profile to see what you wrote on the matter here is what I found out about the 30 x 170 and it is hard to tell from the pics on collecting 30mm stuff as the Rarden has a APDS on it and brass cased where as the KCB is painted steel with deep blue projie & white fuse.
But the latter looks very close then so does the Rarden I would need a further breakdown of case dimensions like neck length/shoulder angle it has the width of case & rim but its the shoulder I think that is different as the 2 are not interchangeable.

From the web page I found on 30mm stuff

"30×170mm"

This was a Hispano-Suiza development from the 1950s, but has a connection to an earlier round as the base dimensions are exactly the same as the Hotchkiss 25×163, surely not a coincidence. The gun was originally known as the HS-831 but was renamed the Oerlikon KCB when the companies merged around 1970. It has exclusively been used in the anti-aircraft role, in both land-based and naval mountings. The cartridge cases were originally of brass but these are now rare, and steel cases are much more common.

"In the late 1960s the case design was adopted for the British Army’s Rarden AFV cannon, but the material reverted to brass. Rarden and KCB ammunition are not qualified as interchangeable. The Rarden round shown above has an APDS projectile."

It also gave the M.E for the round at 207,000Joules which equals 154,888.051Ft/Lb’s of M.E