Using the stock coil may be going too big if there is trash and/or iron or mineralization. Try a smaller coil and you might just get deeper. Like the other guys said, if there is time to dig every signal then do that. You'd be surprised what you can dig in the pull tab or foil zone if it's an old site. Flying eagles, fatty indians, gold, tokens, buttons, jewelry and numerous relics can all be passed over if we're cherry picking. Also, getting surface stuff out of the way exposes the ground beneath to your coil. If the guys you are hunting with are kneeling down and digging all the time and you're just scanning waiting for a textbook signal then that would explain them finding more. They're not just digging textbook "good" signals. If they are digging less holes than you and still coming away with more then it could be for several reasons. 1. You're swinging the coil too fast 2. You're discriminating too much(maybe too much iron mask) 3. Got the machine on semi-auto sensitivity instead of manual and that's automatically turning down your sensitivity to possibly even single digit number range 4. Your coil is too far off the ground (scrape the ground) 5. You're trusting your cursor position on the screen when it hasn't reset (listen to the tones, the audio ID does not have to reset like the screen does, "the tones are true, the cursor lies") 6. You're not rechecking sounds you hear. If you hear a weird sound then analyze it by finding out exactly where it is and scan it with the center of your coil, see how big it is, see how deep it is, see what it sounds like on the edges of it as well as the center, and here's the most important one-see what it sounds like scanning from a different angle-walk around it while scanning. You might just be able to find an angle where it sounds like almost a textbook signal then feel good about digging it 7. You're in the wrong area of the site. You probably figured out already that there might be areas of the site with no goodies no matter how many holes you dig. Go back to where most of the goodies were dug and try digging everything there.
Hope some part of this helps.
Good luck
Neal