Beretta al391 Urika

[paddy..]

My barrel on my al391 seems to be loose, even when I've yanked the fore end lock nut right up.What a bitch they lock nuts are man, nipped it up on fri night, had to get a pair of long nose pliers for the nut, to get it tight enough to stop the barrel moving. When done with my hand there seems to be about an 8th of an " gap. After shooting sat, the barrel is loose again, ***, any tips would be great. cheers