Are they Sig sights? Sig dovetail grooves are normally very tight and one way like CZ's are. Loctite really isn't a great option as it counts on a tight fit and the absence of air to set up. There are a few things you can do but I would need an answer on my first question and some point on how loose the sight is.
Take a centerpunch and small hammer and peen the bottom of the site about six or seven times along a centerline with the site held securely without maring it (wrapped) to raise it's interference and push/punch it in from the left. You can peen the site from above and on center later when a zero has been determined.
anything to "occupy" some of the spacing ( gap) of the bottom (flat) of any dovetail and the bottom "flat" of the sight body itself......this pushes up against the dovetails slot ,front and back...this being said yes a thin shim can work but , if it shifts and moves as you are driving in the sight, it can AND WILL come out and show on the other side.......so as often noted, just a few divots with a punch and the slide sitting on a HARD , level surface, stake just a few holes, divots, punch marks, whatever you want to call them, its called "raising metal", just enough to "tighten" up the gap (looseness) and yes, if you take and move the sight off and on and off and on, you are going to loosen it up again,,,,,those punch marks do flatten off with going on and off...........no need to use Loctite or some such, as the first time you try and drift the sight, you break the integrety of the Loctites "bond".....and yes recoil can do that also............same goes for "pistol whipping" 8) :roll: :wink:
Not a good idea to center punch the night site as it may break the vial seal and let the glowie stuff (technical term) leak out. Cut a long thin strip of pop can wide enough to fit the width of the dovetail cut in the gun. Try to slide sight in about halfway with the strip of can centered in the slot and under the sight. An adult beverage can can also be used if so inclined. If it is too tight, file the bottom of the sight until you can push it in by hand half way with the shim underneath the sight. Once you get half way there, use a brass rod to LIGHTLY tap it in place. A wood or plastic dowel is better and not so hard on the sight. Once it is in place, use a sharp thin blade to score the metal strip and break off the excess.