So once I was there, gandering, Jason Gilbert showed me one of the things that he says is really hot right now, and that's the .22 caliber conversion top ends for the ARs from Tactical Solutions. They're lightweight and allow you to practice with your AR by just swapping out the top ends, no fitting, no nothing. Swap and shoot, no hassles, and he says that they're reliable as well. At $569 they might be a bit pricey, but they're extremely well made and well finished. I've never seen anything from Tactical Solutions that wasn't top-notch.
Something to consider if you're looking for a low-cost practice solution in this time of rising prices, or just want to be able to plink or hunt small game with your AR.