Rifle Gap never had a huge walleye population, but according to CDOW biologists, it once had a nice population of them. They have always been hard to catch though because of all the food, mostly crawfish and young stocked trout.
The problem wasn't the trout, but that Rifle Gap was OVERSTOCKED. It already had a small naturally reproducing population of browns and rainbows that spawned and lived in east and west rifle creeks.
Starting in about 1995, Rifle Gap started getting oodles more trout stocked than it ever had before. Myself and other anglers would catch tons of rainbows that were coughing up small walleyes and bass. We found walleyes and other gamefish up to 8" long in the stomachs of trout.
Trout grow larger and are far more aggressive predators than walleyes. Take a trout and a walleye of equal size, and the trout will drive it away and take it's food.
It was the overstocking that caused both bass and walleye to crash. Then the explosion of perch also harmed the remaining gamefish. The trout primarly forage on crawfish and perch now, and large trout do exist, including a 25 pound rainbow caught in 1997 that was eaten and not verified as a record. Again I saw the photo and it was indeed rifle gap. It's fairly easy to tell fake photos, and this one looked authentic.
Rifle Gap would have MONSTER trout if people didn't keep them all. Reproduction is still very low for trout in this lake, though the browns are completely self sustaining. I would say with all the crawfish, perch, and everything else the trout have to forage on, 20 - 25" rainbows would be the norm if it was only managed for them. It would be almost like spinney or antero.
Their are walleyes left in Rifle Gap, just not many. Those that remain are big, and 10 - 15 pounders exist here. I wouldn't be shocked if a few state record eyes swam in rifle gap. I am sure their are state record rainbows, smallies, walleyes, perch, and browns in the lake. It is very productive with tons of forage. The lake gets pounded and the big fish are very, very wary.
Now pike are in the lake in moderate amounts. I think they will help thin out the perch and will eat some of the excess trout. They may help the lake.