I can't remember the designation of the Colt .25 ACP, but the Astra succeeded it (wasn't one of them the "Cub"?), and I think the guns were made for Colt for a time by them. I have an FIE "the Best" which is supposed to have been made on the same machinery. Now, if all that's true, lock the slide back and turn the exposed barrel until it unlocks and comes out. Release the slide (holding on to it, of course!
) and it's done.
If it's like mine, it's pretty simple. Hope this helps.