barrel break in ?

Break-in is not a myth. It's not going to 'ruin' a gun if you don't do it and it's not going to do anything like make a 3MOA gun shoot sub MOA.

Shooting and cleaning properly will gradually polish the bore, removing imperfections. I've seen it myself with my own rifle and the bore now looks like a mirror after a few boxes. A good 'broken in' bore should maintain accuracy for more shots, because fouling will not accumulate as quickly, and cleanings should also be slightly easier.

It's up to the owner whether to do it or not. It's not really going to make or break a rifle, unless you damage the bore while cleaning. I just use a bore snake and hoppe's #9, and run the snake a few times and it takes care of everything.

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