MN Sniper Style Bolt Handles

I noticed that my brass was getting badly scratched when I shot it. I
realized this was coming from some sort of roughness in the chamber. I
got 3 ft long Ľ in aluminum rod from hardware store. Using a hacksaw I
cut a slot about 1 in deep in one end. I cut a 1 x 2 in piece of Scotchbrite
pad and slid it into the slot. I chucked the other end in a cordless drill.
Soak the pad with WD-40 and wrap the ends around the dowel. While
spinning it with the drill, push it in and out of the chamber. It only takes
a minute or two of this to put a nice polish on the chamber. You only
need to do it long enough to remove any rust and grit and to deburr any
scratches on the walls of the chamber. This may also help with
extraction problems. For the Mosin I polish from the breech end but I
left the aluminum rod long so that I can polish the chamber of my
Garand from the muzzle end. I also used it as a ram rod when I slugged
my barrel.

To determine the correct size bullet to use in my rifle I needed to know
the true bore diameter. Kits can be purchased from places like Brownells
to cast a soft plug in the bore which you then drive through to extrude it
to the outside diameter of the rifling grooves. A cheap and reasonably
accurate way to do this is to drive a soft lead fishing weight through the
barrel. First find one that's about 5/16" dia. If it's a little big you can use
a knife to shave off a little so it's right about .3125. Just a bit of sizing
lube will make it easier. Drop it into the breech and drive it through the
barrel with a Ľ inch aluminum rod. It should be a tight fit but still move
smoothly. If it's too tight and jams just tap it back out from the muzzle
end. When it comes out, it should have a crisp clear rifling pattern. If it
doesn't (assuming your barrel has good rifling) the lead slug was a bit too
small. Take the slug and measure across the widest part by slowly
rotating the slug to find the greatest diameter. A bullet should be about
.0005" bigger to fit the barrel properly. My barrel measured about .3105.
I found that .311 bullets for the 303 British Enfield give the best accuracy
for my rifle.