If you want to use an SKS to hunt deer, in some states that requires a magazine capacity not to exceed 5 rounds. I converted from a fixed 10 round mag to a fixed 5 round mag, just for this reason.
Some people like to blast ammo down range as quickly as possible; for that purpose having detachable high capacity magazines is useful. For hunting wild game, the need to meet hunting regulations, and precisely place the bullet into the target becomes more important; having a low capacity fixed magazine is more useful as it allows resting the rifle on a support, to improve shot placement. The effective range of the SKS round on deer is about 125 yards, and that is about the limit of accuracy with some rifles (they can't keep the bullets in the kill zone past that range). I know that SKS rifles have been used to kill deer; one of my friends did it with a rifle he got from me.
I had some difficulty getting the replacement mag to fully seat when i did my conversion, and it was supposed to be a true drop in replacement. I suspect that removable magazines have a more difficult fitting process; it may be that each converson is peculiar to a specific rifle, and can not be used on a different rifle without refitting to that gun. Hopefully the mag is being modified, and the gun is not.
