You may purchase one at Wal-Mart or Cabelas, along with your diapers or fishing bait.

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Among the largest underlying components of XRT, in trading today Cabelas Inc ( NYSE: CAB) is off about 0.5%, Shutterfly Inc ( NASD: SFLY) is down about 0.3%, and Expedia Inc ( NASD: EXPE) is lower by about 4.9%.

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Once you have decided to purchase a gun from a retail outlet -- it could be a local gun shop or national chain such as Bass Pro Shops, Cabelas or Walmart -- the store enters your name and information into the National Instant Criminal Background Check System, or NICS, via a toll-free number or the Internet, to check the eligibility of the buyer.

CNN: Background checks on gun sales: How do they work?