I friend of mine wanted me to clean his Gen 4 G19. Now I have 3 Gen 3 guns and clean them all the time. The slide on the Gen 4 came off just like all my other ones. I cleaned and lube everything and went to put the slide back on and it gets about 1/16 of an inch to the rear of the gun and stops. I didn't want to force it and break something so I came on here first. Are there any tricks to the Gen 4 that are different from Gen 3? Thanks.