1893 Mauser grouping poorly need some help

Picked a 93 Mauser in 7x57 bore and crown are good it is one that has the hinged floorplate the stock is a nice commercial one but barrel is not free floated drilled and tapped. I put a scope on it group was the size of a dinner plate if you could call it a group. I was using Remington 140 grn corelocks . I am thinking about trying 175 grn bullets or free floating barrel all screws are tight. Well except maybe the ones in my head. Any thoughts or advice is appreciated.

My first inkling is to slug the barrel. It's easy enough, and will arm you with the confirmed knowledge of the bore diameter, etc. See the tutorial below. It is for a Mosin Nagant, but the approach is the same - just use a narrower slug of lead. HTH: http://7.62x54r.net/MosinID/MosinSlug.htm

Thanks Liam I have slugged the bore on my Trapdoor didn't think to do the Mauser I will do that and see what the bore actually is.