Wow...you can hit a huge target. Good for you. I shoot at very small targets.
I also have a Springfield 1903-a3, but it stays in the gun case (4th generation heirloom). If I need to reach out and touch a target beyond 300 meters, I use my
ruger .308. I say beyond, because that is where my 308 is zeroed.
Binary explosive is quite volatile. I've never mixed more than a pound (about a 1/2 quart - the size of a softball or grapefruit). That makes it a pretty small target at 100 yards. From what I've read, just being hit by the shockwave at close range can kill you.
The general rule for binary explosive is 100 yards per pound is a safe distance. A man sized target would be well outside 300 yards if you wanted to survive the experience.