I recently bought a glock 21 and it was shooting great until I had an extended slide release put on. I had it put on by a glock armorer. Basically when I fire a round the slide locks in the rear positon. It is not getting jammed or anything it just stays back. Now I can release it and fire another round and maybe get lucky and fire a couple but thats it. I am not sure if having that new slide release put on has something to do with what is going on, but I can't figure it out. If anyone can give me some advise that would be great.