Please purchase a bugle! We have to keep those call manufacturers flush. And its a good warning sound to veteran hunters that you're in the area.
I personally haven't met a rifle hunter who believes elk bugling unless they physically see the bull making the sound. The majority of bugles during rifle seasons are other hunters following poor internet/magazine/forum advice.
No place in the Colorado rifle seasons for bugling unless you are hunting private land.
Techniques....I'd suggest only using a cow call in rifle season if you have a visual on the elk and are trying to stop them for a shot. Otherwise leave it in your pocket until you actually see elk.
Pressured elk (during rifle season) make very little noise unless they are in a big herd, or just got busted out of cover by a threat. Generally they keep fairly quiet and are not very responsive to calling. There are always exceptions, and mine is just one opinion.
