Back in 1963 when I got my 12-gauge, 3-inch, Super-Fox, it came with three boxes of late 1930s Remington ARROW EXPRESS Magnum Loads. One each #4, #5 and #6. None of the boxes were quite full, a few shells out of each. When I was cleaning out my Father's house in 2003 after I retired I found the pattern sheets I'd shot back then were still there in the basement, rolled up and tucked up in the main floor joists. They showed 79% with the #4s and 85% with the #5s. Also the #6 box with 14 shells was there in the basement too.
ARROW EXPRESS 12-gauge 3-inch Magnum Load.jpeg
Guess I shot the #4 and #5 shells at Columbia Basin Mallards back in the 60s.
I didn't realize at 17 that my 1928 vintage gun was actually made for 1 3/8 ounce loads. I even tried some of the 1 7/8 ounce loads in it, but they made very patchy patterns so I stuck with 1 5/8 ounce loads until bismuth came along.