Have you slugged your bore to find its true diameter? That would be the first step. It doesn't matter what works in another rifle because it may not be the same bore size.
Many people will recommend slugging the bore but I have found pin gauges to be easily and accurately used. Amazon can provide a few in the range you’re interested in. The other option is making a bore cast from cerrosafe. Make a wad of aluminum foil around the head of a bolt and screw the bolt into your ramrod (8-32 or 10-32) Then center the head of the bolt into the muzzle of the rifle. Melt the cerrosafe and pour it into the bore. Allow it to cool for an hour and remove it from the bore.