For years, if you wanted an AR-15 that shot rimfire ammunition, your options started and stopped with .22 LR. It was cheap, it was fun, and it was great for training — but it never felt like a true step up from your centerfire build. That's changing. Rimfire AR-15 platforms are now being offered in .22 WMR (Winchester Magnum Rimfire) and .17 HMR (Hornady Magnum Rimfire), and the shift is a bigger deal than it might sound at first. Why This Matters for AR-15 Shooters The AR-15 platform has …