525 yard pass through on 3/8" steel gong

[remingtonman_25_06]

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.

[Black Diamond 408]

All of our steel targets on our range are 18"

Br-500 steel 1/2" thick, .408 military ammo will not go through.

using steel for penitration test doesen't work to well , P.O.Ackley shot a piece of arrom plate with a 270 , 30-06AP and a 220swift , the swift drilled right through it and the 06 and 270 barely made a dent.
BUT
shoot a deer with the same three rounds and you'll get alot less penitration from the Swift as the velocity causes it to blow up in the critter instead of a controled expansion.

My 12" gong at 400yds is a piece of 1" thick Alloy 20 plate. I have a 4" ring around the outside on the front and a 10" around the outside on the back made from 12" sch 20 pipe this setup makes one hell of a racket when its hit.
I shot it a 50yds with a 300Ackly and a 190gr MatchKing at 3100fps and it barely scuffed the surface.

[HoytemanPA]

If you want it for plinking on perfectly windless days or have gotten first shot wind reading mastered, the 10" would work, but.... If you are learning wind affect...I would leave it as big as possible. Not knowing exactly where a miss went is a wasted round for me. I use a very large sawmill blade painted white at 820 with a 10 inch orange circle painted in the center. Any more than a faint hint of breeze and I'm either holding the edge of the blade or cranking in windage. This year I'm putting up a plate at 1000. It will be a 30x30 1/2 inch plate with 2 more 30 inch wings of 1/4 inch material.