[Jim K]

I wonder if you are putting the barrel in the slide right before installing the slide.

Put the barrel in the slide and turn the barrel clockwise until the three locking lugs turn sideways into the cutout made for them. Then put the recoil spring and guide into the hole in the frame, guide to the rear. Put the slide on the frame, making sure the front of the recoil spring fits in the hole in the front of the slide and retract the slide.

When the slide reaches the slide stop, the stop will kick up into the notch, which is the right position to turn the barrel 90 degrees counter clockwise with the lugs fitting into their slots in the frame.

Jim