the abrupt start of the grooves is the lead angle that is important to the start of the bullet making its way down the bore
my projectiles dont jam or get stuck because l have my reamers made with a lead angle that compliments the bullet l am going to use so there is no abrupt start,
better chance to start straight better chance to shoot straight although some say its like wearing the lands down at that point, l suppose it is
you could liken this to a car having to jump over a curb before it gets started and is something to consider when having a new chamber cut
l'm glad your happy with how the rifle is going and there is no guarantee that even an air gauged barrel will shoot better,
but honestly l haven't seen one yet that wont, 1/2" moa is the max average l would hope for but usually nearly always get way less, at least 1/4 moa max
when having a rifle rebarreled it is essential that the receiver face is squared to the bore, the threads chased with the lugs lapped, bolt face squared, then make the barrel to suit and fit. everything squared to the bore or you are really pissing into the wind and tossing a coin, but who knows you may get lucky
air gauging is how some barrel makers check for uniformity of the bore and is how they are graded, its the difference between knowing you have a really good barrel
as l said earlier l would be advising to shoot the rifle for a while, maybe 200 rounds then seriously look at tuning your loads,
l'm sure you will have a real winner
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