hello,,are you sure this is an arisaka,,i don't recall them having a detachable mag,,they do have a hinged floorplate that can be opened with a lever in front of the trigger guard,,the carbine models were the type 38 carbine and the type 44 which had a side folding bayonet ,,heres a site to help ya id the markings
http://www.radix.net/~bbrown/japanese_markings.html ,,this site will help you with the charaters marked on the rifle and will show you how to determine which model you have ,,if the link doesn't work search "japanese rifle markings"and you will find it ,,values for these have rizen in the past 10 years and depending on which one you have 350 is a good starting figure.. depending if it's numbers matching (the serial numbers last 3 digits should be on any part that has a number) and if the mum on top of the receiver is present or ground or defaced ,,caliber for a carbine is 6.5x 51 i beleive or commonly called the 6.5 jap,,the other battle rifle used by the japanese most commonly found would be the 7.7 jap and they would be a type 99 arisaka ,,these were the most common variation of the arisaka used during ww2 ,,there are other models with special features but basically you find these 3 variants these days ,,
bigcurt