I just checked my 6320 for my lw operator, it's the same thing but left handed. The adjustment screw by the trigger guard is the way to tighten it down. It does just spin if it's very loose, but if you hold the back nut with your thumb then use the allen wrench it should tighten down. Your screw my be crossed threaded, so try and remove it and check for stripped threads if it doesn't work. My holster does not have any movement once the ALS Locks it in place. Check the screw that holds the ALS to the top of the holster that may be loose.

For anyone that may have the same problem with this I'll post what I was told by safariland. A little bit of up and down movement of the gun once the ALS is engaged is normal. As is a a bit or rattle with some models. I asked if it would be ok to heat the kydex at the muzzle and press it to the gun to get a tighter fit and she said that would be ok and to just e careful with it. So I will try that and post results. I'm wanting to minimize movement of the gun to prevent unnecessary finish wear and get rid of the rattle.

Safariland also said due to the locking nature of the ALS that the gun will not fit the sale way as with a 6004 or 5288 where the gun locks in and is held by tension.


Update:

I I cut a slot in the tension screw in order to remove it and see if there was anyway to adjust anything and retighten. No dice, The holster is just loose. So I heated up the holster near where the muzzle end of the slide would be, inserted the gun inside a ziplock bad and knelt on it until it cooled. Now the holster fits the gun well and there is only about 1/16" of up and down movement, there is no rattle.

Now I just need to practice about 1000 draws with the release.

Depending on the gun, I have some looseness in my ALS holsters. None fail to retain the pistol, I can shake the hell out of them and whip them around and the holster stays put until I activate the lever. I may do that spacer trimming, honestly it hasnt been much of an issue.