My experience is the new Singer branded bobbins are narrower at the edge than the vintage ones. New bobbins didn't fit the bobbin winder on my 1948 66. The guide was wider than the bobbin. I ended up filing the guide down so the bobbins would work on it. The new metal Singer bobbins are garbage. The plastic ones are far more consistent in size.
You might try a different brand and buy from a quilt shop or actual sewing store. Chain stores like Joann's and Walmart only carry the crappy ones.
Vintage bobbins are like gold to me. I get them whenever I see them now that I've learned there is a difference.
Rodney