slugging question 303 British?

[wileynet]

just slugged 303 enfield, used egg sinker, nose where it left the bore measures .299 and at the base,  grove measures .310 at the middle and .314 at the base same over 3 sinkers what size cast bullet do i need

[curator]

The most important measurement is the throat in front of the chamber. If your bullet fits the throat it will shoot accurately. If undersize there is a possibility that it will tip and shoor poorly. Contact Veral Smith at LBT and send him a throat slug so he can cut a mould that will cast boolits that will shoot accurately in your gun. He has made several moulds for me and all of them shoot fantastic in the gun they were made for. Alternately, use the Lyman # 314299 made from air-cooled wheel weight metal and load over a filler like cream of wheat or plastic shot buffer. The filler will protect the sides of the undersize bullet from hot powder gas until it obturates sufficiently in the bore to seal it correctly.

[Nobade]

For 303s I have had good luck with using a bullet that will just enter a fired case. No need to measure the bore, just use the biggest thing that will fit. Oversize on cast bullets won't hurt anything but too small sure will. And the above advise of using fillers is right on as well, they let you do things you couldn't otherwise do. Just watch for excessive pressure since fillers will boost pressure - a good thing, you use less gunpowder for the same effect.

[Greg B.]

Who made your .303? I have a Long Branch #4 Enfield. It has an odd number of lands and groves. So if I slug the barrel and use dial calipers to measure (I should use a micrometer which I don't have) one caliper blade is on a land and the other in the groove. It is possible to measure it accurately but I don't know how. Nobade's suggestion is a good one. 
 
Greg B.

[wileynet]

found in one of my dads old gun books, that you can gently spin the slug in the calipers till you get the meugerment