Once the basic configuration of the new British rifle was determined, the next step was to build a series of prototypes. The design that took form was basically a bullpup copy of the Armalite AR-18. The design team at Enfield were mostly senior draftsmen, with virtually no firearms experience among them. To make things worse, most of the design team was regularly rotated onto other projects, preventing them from developing any project experience on the rifle.

Several prototype batches were made (typically of a dozen guns each, both IWs and LSWs), all in the unique British 4.85x49mm cartridge, with a variety of different feature sets. Through the different patterns, configurations would change on the safety (push button vs lever) fire selector (push button vs lever), and magazine catch (straight-in side lever vs rock-in side lever vs rock-in rear paddle). At this time, plans still existed to make both left- and right-handed versions of the final gun, so prototypes of both were manufactured.

Because cost-cutting measures had not yet been forced on the project, these XL-60 series guns were generally reliable, at least in normal conditions. They are quite comfortable to fire, with a cartridge very similar to the 5.56mm NATO in practical terms. There is nothing particularly wrong with that cartridge, but it would be dropped when it lost NATO trials to the Belgian SS109...but we will address that in the next episode of the SA80 history.