Many customers in the market for a new AR-15 purposely buy an entry-level rifle, fully intending to accessorize it “up.” That upgrade usually means a better trigger, a different handguard and other higher-quality features. Of course, these customers are very important to the tactical retailer, both for the initial rifle sale and the purchase of accessories to follow.

But just as important are the number of shooters who want a higher quality AR-15 from day one. These...