It is not necessarily a function of score. At Aberdeen Proving Ground one of the indicators is known as a Yaw Card Study.
Easiest way to do this is load 100 rounds of your favorite known good load.
Yaw cards are shot at 1000 inches (about 27.77 yards). When you have a new barrel or a new match rifle go out and put up a 3X5 parallel card with a aiming dot on it and shoot ten rounds. Your individual shot holes should be perfectly round.
Record the date and the number of rounds on your barrel and repeat at each 1000 rounds for perhaps 5000 rounds and upwards depending on how well you clean your rifle. You should still be printing round holes unless you have something like a 300 Win Mag or one of the hot 6.5MM or7MM rifles. Magnums and 6.5/7MM barrels may start showing elongated holes at 500 to 700 rounds. This is the first indication the barrel is getting tired
As long as you don't increase the weight of your bullet you should not see elongated holes. Now if you change to a heavier bullet you may see elongation quicker.
At long ranges you will probably see less Xs and then less 10s at first. Chrome moly barrels tend to go out slower than stainless barrels and they last maybe 800 rounds longer and go all of a sudden.
Rejection of a barrel at Aberdeen was when the bullet indicates a 15 degree angle.
On a service rifle yawing may well be the fault of the muzzle crown as when the crown wears the groups will open up. Basically the shorter the barrel the more pressure remains at the muzzle with associate wear.
You can get by with a bolt gun longer because you can pull the barrel and recrown it setting it back about .025" per season. I have seen bolt guns with no riling 3 to4 " down bore that shot 1.5" at 300 meters as the crown was still good.
Thus I recommend the erosion gage for the MUZZLE. The one I have came from CMP, they quit selling them for a while but I understand they are back. It is 7.62 and looks like a loaded bullet at first glance. I have one inbound from PTC for a 22 cal muzzle checking.
Easiest way to do this is load 100 rounds of your favorite known good load.
Yaw cards are shot at 1000 inches (about 27.77 yards). When you have a new barrel or a new match rifle go out and put up a 3X5 parallel card with a aiming dot on it and shoot ten rounds. Your individual shot holes should be perfectly round.
Record the date and the number of rounds on your barrel and repeat at each 1000 rounds for perhaps 5000 rounds and upwards depending on how well you clean your rifle. You should still be printing round holes unless you have something like a 300 Win Mag or one of the hot 6.5MM or7MM rifles. Magnums and 6.5/7MM barrels may start showing elongated holes at 500 to 700 rounds. This is the first indication the barrel is getting tired
As long as you don't increase the weight of your bullet you should not see elongated holes. Now if you change to a heavier bullet you may see elongation quicker.
At long ranges you will probably see less Xs and then less 10s at first. Chrome moly barrels tend to go out slower than stainless barrels and they last maybe 800 rounds longer and go all of a sudden.
Rejection of a barrel at Aberdeen was when the bullet indicates a 15 degree angle.
On a service rifle yawing may well be the fault of the muzzle crown as when the crown wears the groups will open up. Basically the shorter the barrel the more pressure remains at the muzzle with associate wear.
You can get by with a bolt gun longer because you can pull the barrel and recrown it setting it back about .025" per season. I have seen bolt guns with no riling 3 to4 " down bore that shot 1.5" at 300 meters as the crown was still good.
Thus I recommend the erosion gage for the MUZZLE. The one I have came from CMP, they quit selling them for a while but I understand they are back. It is 7.62 and looks like a loaded bullet at first glance. I have one inbound from PTC for a 22 cal muzzle checking.
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