The mod increases the time before the game holsters the weapon. By default, the game removes weapons 3 seconds after the last use, but there is an option in the playertune.xml settings that allows you to change this.
Just add the line to the end of the playertune.xml file, and now the time can be adjusted to your liking. The mod already includes a playertune.xml file with this setting (by default the time is changed to 10 seconds).
To install the mod, open the file tune_d11generic.rpf in MagicRDR, go to tune/player/ and replace playertune.xml with the new file (you can change the time inside playertune.xml before replacing).
Also included is an alternative method for adjusting the time without having to edit game files. Simply extract the SUWSF archive next to your RDR.exe and you can configure the weapon stowage time in the INI file without having to repack the game files every time. This method reduces the likelihood of conflicts with other mods.