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 ---- 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.