The Remington Arms Model 241 Speedmaster, an autoloading rimfire rifle, was manufactured from 1935 to 1951 from a John Browning design.
The Remington Model 241 (and indeed all the semi-automatic .22 rifles based on John Browning's design) is a takedown design in which the barrel can be easily separated from the receiver to shorten the rifle's length for ease in transporting.
The Remington Model 241 is very similar to the Browning SA-22 with the significant difference being the way in which the barrels are adjusted so that they fit snuggly against the receivers when the rifles are fully assembled.
Persons wishing to make adjustments to the Model 241's barrel tightening mechanism must become familiar not only with the use of the dual-sided nut (that fits in the hole in the front of the receiver) but also how that nut is locked in-place (so that it will not accidentally turn once it has been set as desired).
To adjust the Model 241's barrel tightness it is necessary to first loosen the dual-sided nut so that it can rotate and thus have its depth within the receiver changed.