Developed in the 1910s, the Parker-Hiscock system converts a 303 caliber Enfield service rifle to a 22 caliber repeater, suitable for both basic marksmanship practice and "rapid fire" on small bore ranges. The barrel is sized for 22 and the bolt reconfigured for rimfire and beveled on the underside (more on that later). The true heart of the system in in the magazine, a spring-loaded apparatus housed in the body of a conventional 303 magazine. The apparatus, numbered "G5337" or "337" on the components, integrates a single stack magazine, a push rod assembly, and a beveled top. When the bolt opens, the magazine pops up to align with the breech, and the closing bolt first drives the push rod to deliver a round to the breech and then the beveled surfaces of the magazine and bolt interact to push the magazine back down into the housing. On follow-up shots, the magazine doubles as an ejector mechanism for the spent casings, physically pushing them out of the rifle when it pops up. 303 mag converted to a 22 caliber mag. While novel and mechanically intriguing, the Parker-Hiscock had a very short service life, being added to inventory in 1915 and declared obsolete in 1920. Standard blade and tangent sights are present, with the BSA logo on the barrel and the 1915 dated Enfield socket remarked "Sht.22/Mk IV*". The volley sights have been removed from the stock, which is fitted with a tan canvas sling and bears a "Canadian broad arrow" stamp on the right side next to a blank brass disc.

Fine as arsenal upgraded, with 80% of the blue finish overall, showing areas of brown and gray patina, along with some mild spotting and handling marks. The stock is very good, with some light chipping around the front volley sight base, along with scattered dents and scratches. Both the rifle and magazine are in fine mechanical order. A mechanically interesting device and a rarely seen piece of British military hardware, likely absent from many collections.