Folding magnifiers are so handy yet inexpensive that you should own a couple spares (including one in the range box). I bought my magnifier in a book-store, but you can also find them on the web at FoldingMagnifier.com and WidgetSupply.com starting at just $1.95. To see the finest details, Widget Supply offers a powerful 17X/50X slide-out magnifier with a built-in, battery-powered LED light. With that gadget, you can easily see any minute flaws in your barrel crowns. That’s important because crown damage can cause hard-to-diagnose accuracy issues. We’ve known guys who spend weeks tinkering with loads, when the real problem was a worn-out or damaged crown.