David, #3 #4 weight barrels are well pretty heavy for a low wall. Most common are either a #1 or #2 and the low wall basically shot the pistol cartridges of the period. 25-20 SS,25-20 WCF,32-20 WCF and 38-40 WCF and 44-40 WCF. If you are looking for a 25-20wcf or 32-20wcf check out TJ's liners.And John Taylor of Taylor Machine is the gent to install your liner.Frank