A few years ago I picked up a used percussion Lyman GPH, LH in 54 caliber. I'm just now getting around to shooting it but I cannot get the set trigger to work. The front trigger will fire the lock but is stiff. The rear trigger will not set the front trigger. I've pulled the triggers from the stock and nothing looks modified to me. I've moved the adjusting screw in and out with no joy. What am I doing wrong? I'll admit this is my first foray with set triggers.