Mine came with a allen wrench and there is a screw under the rear part of the slide that adjust it. I have had the gun since I was a kid and never touched the screw until this year when I pulled out the manual to due a good tear down and cleaning and found the wrench then I read a little figured out what it did and adjusted the trigger. It was a great trigger before and now it is so light it is scary but I like it. So see if there is a hole under the rear of the slide. The allen wrench is very long and the screw is not visible but the hole is. I do not think every model is like this. If no hole go over to rimfirecentral, go to the browning forum and then to the buckmark and at the top is a sticky that has a trigger job that can be performed on the other kind of buckmark. It involves flipping a spring over... is about all I can remember but the link is step by step with pictures. I am at work now and can not get to rimfirecentral, the site it is blocked. I will try to find it later and post the link here.
I was shocked when I saw it and the praise people gave it on how much it helped there trigger but I latter figured out I had a different kind of buckmark with an adjustable trigger.