Barrel Erosion ?

[Moman]

I lost quite a bit of accuracy on a Rem 700 in 300 Win Mag and found that where the 180 grain Accubonds used to be seated .020 are now .042 . This is with the same lot of bullets and were measured last summer with a Hornady LNL. I also have an old half used box of Sierra 180's from when the gun was new that the bullet seating depth has increased a total of .032. I am sure this is due to errosion and I will try a new seating depth but my question is how detrimental is this? Do I need a new barrel? How much overall erosion do you allow before rebarreling?

 

[JeffVN]

Yep that is throat errosion. How many rounds do you have through it? If the number is approaching 1,200+ it may well be time to start looking for a new barrel - especially since it is now showing visible signs of accuracy degradation. You can chase the lands, to get your jump distance back to the original distance, and that may bring back teh accuracy for a while, but I suspect you are on the downhill slide of a useful barrel.

JeffVN