Gas regulator for 7kg Calor Butane Bottle

That is not a regulator. It is an adapter which then connects to a bulkhead mounted regulator.

I have found the type of adapter you have very easy to use.  (The ones generally available now are round and smaller, but I find a little bit more tricky!).

When you are pushing it onto the cylinder, it helps to press the control button in as you push down....as if you were detaching the cylinder.  If it is still tight, a quick spray of silicone lubricant onto the bottle end helps a lot .....or even a little bit of saliva!

Well thanks for that but 'pushing'  it onto the cylinder, even with the 'control' button pressed it is a nightmare each time requiring me to jam a iron bar of sorts through the top of the bottle and top of the 'adapter' to dd pressure to get it into place. maybe it is faulted. ?

Ray

Maybe the adapter is just seized and needs lubricating?

You haven't by any chance got a 20mm adapter?  Calor bottles are 21mm (and I would not have thought you could even force a 20mm fitting on).

That was my first thought when i read the OP but the label (although upside down) in the first photo appears to indicate the dia as 21mm.

But it shouldn't need forcing with a bar, something is very clearly wrong......

Dear Vicmallows,   Although I said the mechanism appeared to work well enough I have taken your advise. I applied some silicone spray and left it a little while and it seems to have done the trick. I had just assumed a fitting issue . I suppose the silicone has help with that and mechanism operation. Thank you.  Hard to believe I have put up with this for years. 

Ray

Even worse are Spanish bottles with 35mm JUMBO push-on connector. Sometimes they can be a real struggle - until you apply a little lubricant! (due to the very large external rubber sealing washer).