In the case of the OS Max .46 AX, ABL is ABN. The difference is that a copper layer has been laid down on the brass liner before the nickel finish coat. That copper layer assists the nickel in bonding to the brass liner core & is intended to eliminate the peeling liner syndrome common to the SF (ABN, not ringed), FP, FX & LA series of OS engines. Break-in should be the same as for the FX ABN engines (& the same for ABC/ABN engines from any manufacturer).

Numerous well-regarded model engine engineers & experts determined quite a few years ago that a rich break-in actually damages the tight upper cylinder fit of modern ABC/ABN engines (and ABL). You may follow the OS directions if you wish -- it is your engine, but many well experienced ABC engine users no longer use that rich mixture method.

Currently, the best break-in results are considered to come from using fuel with a nitro content similar to that of the intended end use, & with at least some of the lubricant being castor oil, & with total lubricant content not less than 18%. The engines are run at full throttle, at a rich 2-stroke (just barely past the 2/4 transition) for a period of 2-3 min, then they are shut down and cooled off completely. The cycle is repeated until total run time is about 30 min. The engines are then leaned out to peak rpm & observed for an rpm-drop. If they won't hold peak RPM, then additional break-in running is added.

Following break-in, for regular use the engines should be adjusted for peak RPM, then richened up until full-throttle engine speed drops by 300-400 revs. You can do this by ear -- peak the engine then richen the mixture until the revs just start to drop.