My son uses a 20 gauge 870 with 3" #2 buck and I limit his shots to 40 yards. He has dropped 3 of the five deer he has killed in the past 2 years in their tracks and 2 others went less then 100 yards, the 2 bucks we had to track and the 3 does fell when he pulled on them. Wolfman who makes the 3 1/2 000, I have not ever seen 000, only the Nitro and they are over $100 for 25 shells.