Winchester USA Ready Large Pistol Match Primers Box of 1000 (10 Trays of 100) Winchester Match Primers are the same primers used in the match grade Winchester USA Ready ammunition. These primers are built to exacting specifications for shot to shot consistency. All primers are constantly and rigorously tested for consistency and sensitivity at temperatures and conditions far beyond the range of normal usage. Winchester guarantees better sensitivity for more positive firing in all guns, carefully-controlled weights of primer mixtures, consistency in size and quality, precise measurements and tolerances for anvil heights and stability in extremes of temperatures and humidity.