You know, I see this issue a lot, and I seem to recall having it when I started, but I haven't had any issues with archers using the range in a long time. Here's my typical setup:
Put archers in squad with archer uniform
Have bolts (Ideally in a binless stockpile, but since yours have bolts this isn't your main problem)
Put a bed in the room with the targets. Make a room out of it, assign the archery squad to train on this bed (This is a barracks)
Make a room of each of the targets, assign each target to allow the squad to train on it.
(Now you have a barracks room from your bed, with archery targets in it, with each of those targets also having a room. So you have a bunch of overlapping rooms)
Have the squad scheduled to train. Default training orders are fine.(Active/Training)
This is all I do, and so long as they have access to xbows, bolts, and the training room, they will go and use the archery range while set to train. They will also do so when they aren't set to train, albeit at random when they feel like it. But they definitely use the range more when set to train.
Another thing that might be contributing, is that from what I've read, very low skill archers are less likely to use the training range. Now, I use my archers to hunt the various wildlife on my map, so that activity could be helping me get over that initial low skill hump that most people notice.
Finally, remember these dwarves are lazy and live to disappoint you. No matter what, they're not going to stick to archery training as much as you might want them to. But they certainly should be training at least sometimes when set to train.