I tried rattling Muleys once to see their reaction. This was a few years ago in early October.
I used some antlers from the previous year and rattled while hiding behind some brush. Two bucks were 60 yards below me feeding. I started out really light and got a little more aggressive after several minutes of not getting a response. The bucks never did respond at all. Didn't look up, quicken there pace, etc. they just kept feeding toward their beds.
Perhaps these 2 bucks just weren't the right candidates. I've seen several spars beginning from mid September to late November. I've only witnessed one serious spar in late September, most of the fights I've seen before the rut seem to be not as hostile. Maybe you will have better results later in the season.
Good Luck!