A friend of mine dropped off a Remington Model 12 .22 rifle for me to clean up for him. The rifle has an octagonal 24" barrel but no target sights, and the rifle is chambered for .22 short, .22 long and .22 long rifle. The serial number is 715***, so I believe it was made in 1927/1928. It is in quite good condition with 85%+ bluing left and no major dings or any cracking of the woodwork. The 24" octagonal barrel would indicate that the rifle isn't the 12A model, but there are no markings antwhere (I did look everywhere) that would point at any of the other variations (12B, 12C, etc). Any ideas of would I should be looking for? Another question - the rifle is having some difficulty with extraction (not ejection) of spent rounds. It does look like there are some scrape marks on the casings that might indicate a burr. Do I just need to polish the chamber, or are there other options? The rifle has plenty of rifling left.