Also put the lock on half cock position before setting the triggers.
That shouldn't make any difference in the sear arm position, but on some locks it does.
As the other fellows have said, the problem is probably with wood being in the way. So definitely start there.
Also pay attention to the depth of the trigger mortise. How deep is the trigger sitting in the mortise? The trigger plate does not need to sit any deeper than the finished surface of the stock. So, if a whole lot of trigger adjustment is needed on a pre-inlet stock, sometimes it is because the trigger mortise has been cut in a little too deep and the trigger is just sitting in too deep. The trigger plate doesn't need to sit down in a hole lower than the surface of the finished stock. If that's the problem, you can just glue in some hardwood shims under the trigger plate to make the mortise more shallow. Don't fret over gluing it wood here. It is a common fix.
If you've resolved any clearance issues with the lock out of the stock and the trigger plate isn't sitting in deeper than necessary, you may still find that (with lock in place) the front trigger needs more clearance in relation to the sear arm. (Birddog6 mentioned this and the tutorial explains it with diagrams). If that's the case, then you will need to make some adjustments there. But do not cut into or try to thin the sear arm to make adjustments. It can be cleaned up on the bottom side if it is rough, but otherwise it needs to stay as strong as possible.
Some adjustment to the height of the trigger bars can be made by carefully cutting down the top of the bars, especially the area that contacts the sear arm. But pay attention to the front trigger bar, as that's the one that usually needs attention.
But, again, the problem is almost certainly with wood. And Birddog6 has given you clear instructions on how to deal with that.
If adjustments are needed to the height of the trigger bars, keep the rear trigger bar as tall as possible. The height of the two trigger bars does not need to be the same. They do different things, so their height can be different. The rear trigger is the one that jumps up to trip the sear. The front trigger bar is mostly there to make it easier to release the cock from full position down to rest position while you pull the cock back gently with your thumb and then release it slowly to the rest position. The front trigger bar just needs to lift the sear while you are holding the cock, so that the nose of the sear will clear the full cock notch. So it only has to overcome the weight of the sear spring, and it doesn't have to be as tall or strong as the rear trigger bar.
(Sorry I keep messing with this, editing it. I'm trying to make the sequence easy to follow.)
