The carbine barrel was short and a round nose FMJ bullet indicates military surplus ammunition. The combination guarantees less accuracy.
If he was a cunning assassin and intended to fly below the radar, he would have bought a surplus M98, keep the action, re-barreled the rifle, bedded in new stock, and developed a custom load with a spitzer bullet.
Not the best of weapons I'll grant, the Italians weren't particularly known for being great gun smiths but since a carbine is a lighter rifle originally meant to be carried by mounted troops it would do the job. Oswald wasn't going for distance here. He just need a weapon with enough punch at a short distance to do the job. In addition buying it through the mail with a false name was a simple way for a simpleton like him to get the gun under the cover of anonymity.