You are glueing both pieces and waiting a few minutes for them to get tacky, right? Then you put them together. It should stay on forever. I just used a contact cement at the Home Depot...didn't even check the brand. Works great.
Yeah I am waiting for them to get tacky, I am getting better results now. I have two out of three that are holding after dropping on the ground hundreds of times, I will keep trying on the other one, until it holds.
Barge cement, an industrial contact cement, works well but is hard to find. Brownell's recommends Black Loctite which replaced the Barge cement in their catalog. I've used the Black Loctite with great results but i would assume the 3M trim adhesive is simialr.