I have a barrel that only has perhaps 50 or so rounds through it that seems to be showing some pitting near the muzzle... call it the last 1.5-2" of the bore. Does anyone have any idea what may be causing this?
The details are that it's a 30" Bartlein chambered and set up by a very well-known and highly regarded shop, and the chambering is 338LM AI. I should also note that the barrel has gone through a Melonite process (through the shop/smith that did the rest of the barrel work). I have owned it for several years, and have only recently gained enough confidence in my shooting/loading skills to put this barrel into service. Saturday was the first time I have run full-house loads through it... 300 gr Bergers with a starting load of 105 gr of US869, and finishing at 111.8 gr over the course of 20 rounds. I should note that I started seeing 3000 FPS velocities around 111.0 gr (pulling the trigger is, uh, an experience). There is a muzzle device installed; a TBAC 338 BA brake/mount (no can installed for yesterday's shooting).
In any event, I got home and was too beat to clean the rifle on Saturday, so I did it yesterday. Using ye olde Lyman video bore scope, I noticed what appears to be the pitting that I mentioned earlier. Deeper in the bore is fine, and the chamber/throat looks great. Using the Lyman, I took a couple pics of what I am talking about, along with an area slightly deeper in the bore where the pitting seems to start (that's the crown towards the right edge of the first pic):
I should note that this bore has never seen a brush of any sort, so we're not looking at a brass brush being reversed in the bore or dragged across the crown. I can't really comment on accuracy, given that I was just doing a pressure ladder and no two loads were the same. I CAN say that the 20 round pressure ladder was a group with relatively little in the way of horizontal stringing, but spread over probably 2.5" vertically (as you'd expect for MV variance of 250-ish FPS). So... any ideas what may be going on?
The details are that it's a 30" Bartlein chambered and set up by a very well-known and highly regarded shop, and the chambering is 338LM AI. I should also note that the barrel has gone through a Melonite process (through the shop/smith that did the rest of the barrel work). I have owned it for several years, and have only recently gained enough confidence in my shooting/loading skills to put this barrel into service. Saturday was the first time I have run full-house loads through it... 300 gr Bergers with a starting load of 105 gr of US869, and finishing at 111.8 gr over the course of 20 rounds. I should note that I started seeing 3000 FPS velocities around 111.0 gr (pulling the trigger is, uh, an experience). There is a muzzle device installed; a TBAC 338 BA brake/mount (no can installed for yesterday's shooting).
In any event, I got home and was too beat to clean the rifle on Saturday, so I did it yesterday. Using ye olde Lyman video bore scope, I noticed what appears to be the pitting that I mentioned earlier. Deeper in the bore is fine, and the chamber/throat looks great. Using the Lyman, I took a couple pics of what I am talking about, along with an area slightly deeper in the bore where the pitting seems to start (that's the crown towards the right edge of the first pic):
I should note that this bore has never seen a brush of any sort, so we're not looking at a brass brush being reversed in the bore or dragged across the crown. I can't really comment on accuracy, given that I was just doing a pressure ladder and no two loads were the same. I CAN say that the 20 round pressure ladder was a group with relatively little in the way of horizontal stringing, but spread over probably 2.5" vertically (as you'd expect for MV variance of 250-ish FPS). So... any ideas what may be going on?
