First, never use "on-line" load data unless it is from a reliable source. An example: Hodgdon (makers of H335) recommends a
maximum load of 42.0 grains of H335 behind the 150 grain bullet, not the 45 grains from your "on-line" source. Go here for their reliable data:
http://data.hodgdon.com/cartridge_load.asp
While you can use them, there is no need for a fancy TSX bullet in the .303. It's velocity window works great for standard cup-and-core bullets. Due to the great variation in the bore dimensions in Lee Enfields, you will have to be lucky to get good accuracy from the hard copper Barnes bullets since they need to match the bore diameter closely to give good accuracy. You will have just as good or better overall performance from a Speer or Hornady bullet in this weight range.
I only shoot 174-grain cast or 180-grain Speer RN bullets in my Lithgow SMLE MkIII* rifle. Light cast loads will group in 2 moa, full-power 180s about 3 moa with issue sights. The latter works very well on deer in brush and timber.
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