You do not need Oval. Use any reasonably square load of a slow powder. In 12 gauge 2 3/4 drams of Green Dot under 1.25 oz with
a light primer is the place to start. However, all guns prefer load variations. You can be reasonably sure that a slow powder is the key.
I used to shoot Federal Game loads in a 16 guage. Most people say they are junk, but they worked like a dream out to long range. That's right... no shot cup, cheap powder, soft shot. Suddenly, I started dusting birds. I got ticked and called the supervisor at Federal. In their infinite wisdow, they had changed to high power powder!
Interesting, that old gun was designed with the same Lefever style barrels mentioned above. For any of you who will believe it, I can tell you what is required. My gunsmith measured mine. The barrel has to have full length tapering. The choke cone is long, 3.5 to 4 inches. The lead up to the choke is slowly angled. It would probably also be a good idea to have tight chambers.
If I told you how tight this gun (a cheap gun) shot, you would a call me a liar. Let's just say it takes a while to figure out how to hit with a pattern that small.
