I have had an interest in getting a steel gong for long range practice. I found a big piece of 3/8" steel out on my uncles property the other day. I wanted to see if my 300 RUM would go through it at 525 yards as I just wanted to test out how strong the steel was. I shot it with 2 different bullets. The first was a 125g BT at 3950fps. It made a real loud large splat and I would say it went more than halfway through the steel. Once I seen how far the little 125g BT went, I knew right away my 200g Accubond would go through. So I drove back to the bench and shot 1 Accubond and drove back up there. Yep, it went all the way through and then some. My friend came along with his 30-06 and 168g Combined Technology BT's to shoot the gong. Man, what a difference in power! Ha ha ha, that little 06 just made a tiny little dent was all. So would it be right to say the 125g BT would be sufficient to use on deer size animals? It did penetrate A LOT farther on that steel gong then the 06 and 168g ever will. That little 125g at 3950fps does have some power behind it, its also the flattest damn shooting combo I have come up with. Dont even need target knobs out to 500 with a 350 yard zero. Anyways, I will shoot the gong at 800 yards with my 300 RUM and the 200g Accubond. It better not go through because I want to use the gong mainly for my RUM at 800 yards. I use this gun a little bit for everything from coyotes to elk. What size square should I make the gong? I was thinking 10 inches.