Fergus said:303 bullet diameter is .311
2506 said:To really get the proper diameter bullet for your rifle you need to slug the bore. Get you some .315 diameter muzzle loader lead balls or find a fishing sinker at least .314 in diameter. Drop it into the chamber. With the bolt removed start the lead slug into the bore using a metal or brass rod that you can hammer on. After it has been started drop some 6 inch long hard wood dowel rod pieces that are just small enough in diameter to fit through the bore one at a time and then use your metal rod to tap on them so it pushes the slug through the bore. Let the slug drop on to a soft cloth like a waded up towel or T-shirt. Measure between the high spots which are your grooves in the bore. This will give you the proper diameter bullet you should use. These old war horses have a variable size bore made by war time production and worn reamers or by lots of use. I have one that looked unissued and it likes .311 diameter bullets but I have another one that looks like it has a great bore but it prefers .312 diameter Hornady 174 gr RNSP bullets. If you want to get better case life I have found that by using the cases that have only been shot in one particular rifle and only part sizing, neck sizing with a full length sizer by just sizing the case enough as to just slightly bump the shoulder works great and makes for greater accuracy. But do watch for any signs of a bright ring around the web of the cases. It is best to bend you a paper clip with a little hook end and slip it into the case and use it to feel for a thinning on the inside of the case at the web. These rifles purposely have sloppy chambers. It is so that in the mud blood and trash of a battle field when ammo gets dirty they will still work. It lets the cases stretch a lot. Don't try to hot rod this round in these old rifles. They work best with 174 to 180 gr bullets at around 2300 fps and IMR 4064 seems to be a great powder.
ChrisNZ said:Apparently, the mil armourer's definition of "accurate" for a No.4 was 2" @ 100yds.
If you can get 1.5", I'd wouldn't be wasting time looking for better
Chris-NZ
There is some information on this on this (http://www.303british.com/id28.html) site.jonbearman said:You can correct the headspace by getting different bolt heads which should still be around.