In Feb I chambered and installed a 6 BRA barrel on my BAT SV action. I used my new reamer that had a .075" throat, just so I could get more shank on Bart's Hammer 105s into the case. I had great results the previous year with Hammers.
I started working up a load with H4895 in .2 grain increments and BR-4s. All groups were five shots at 200 yds and measured with my Lab Radar. One load looked promising. I checked the throat and after 45 rounds I had no erosion.
I then shot seating depths from .009 jam to .015 jump. Thought I had my load. It was just under 3/8", 5-shots, 200 yds, ES of 4.
I tested that seating depth with powder increments of .1 grains. The load didn't repeat, so I swapped to Varget and started over. 80 rounds later with Varget and I still had nothing.
So I decided to measure the throat. It had moved .009" in 242 rounds. The chamber on this barrel was the best I had done. When I scoped the barrel after chambering it, the rifling at the throat was crisp and sharp. Also, the chamber diameter was at reamer spec, not enlarged at all. I have known for decades that .005 - .010" of throat movement usually occur within the first 50-100ish rounds as the edges of the rifling round a bit. I have been able to measure that in dozens of rifles. One would think I would have relearned that old lesson going forward, but learning was not yet to take place...........
I had also built my first complete rifle by myself earlier this year, a 300 WSM Light Gun on a BAT B in an LRB stock. I decided that the 300 just wasn't a great choice for 600 yds. While it wasn't bad for 5-shot groups in the LG class, when shooting 10-shot groups in the HG class it just moves too much to shoot it fast enough to stay in condition during a 10-shot string.
So I ordered a .308 BF bolt from BAT B and was going to fit my 6 BRA barrel I had been working with. Turns out headspace and bolt cone clearance were fine, just a little tighter than with the SV, so no machining was required.
I checked the throat with the barrel on the BAT B, recorded that measurement, and went back to load development. As expected, it shot just about the same as it did on the SV. However, I tried an even deeper seating depth and found what seemed to be a node between .013" and .018" jump, but it still wasn't what I wanted.
I wound up discussing all this with @Jet. He suggested I try different primers and brought me some 450s and 400s to try. With the 450s and Varget, it shot a 3/8" 5-shot group at 200 yds, so I thought I had found the load.
The next day or so I visited my friend, gunsmith, and former NBRSA National Champ Curt to check out something on the rifle and get some 450s. While there he showed me how I had a little bit of cock-on-closing, and we were able to fix that by reversing the trigger hanger. In going so we had taken the firing pin fall from about .255 to .235." We talked about how that might require a load adjustment.
So I ran a powder test at that previous seating depth and my load didn't repeat. I went to the range twice that day. I decided the barrel just wasn't going to be a good one. At the match a few days later I didn't even shoot. I went up just to help. I planned to chamber a new barrel and start over for the next match 5 weeks away.
Over the next five weeks I was busy with adding a Single Engine Rating to my CFII, and after that decided to install the DRO on my milling machine before chambering my new barrel. I should have had plenty of time. Of course the DRO took much longer than I had planned, then the Holiday Farm Fire hit and my house was put into Level 1 Evac status (get ready). The smoke was so thick that I couldn't work in my garage.
Well, the smoke finally cleared and the evacuation level was lifted. This meant I could go to the match, but I didn't have a load tuned like I wanted. So I went back and looked hard at my records.
I discovered the best load, shot at the first range session with the 450s, actually wasn't terrible after swapping the trigger hangar. It took .1 grains of powder to shoot a 9/16" 5-shot group at 200 yds. It did shoot worse during my second range session that day (11/16"), but conditions were worse and that was the best I had if I wanted to shoot at the match. Besides, in average conditions it probably wouldn't make a huge difference anyway.
So I prepped all the cases and and then decided I should double check the throat. It had moved another .003". That was enough to move it out of the node. So I adjusted my seating depth and loaded up my rounds.
I told everyone at the match that I had no idea if I was tuned, but since I couldn't make the NBRSA Nationals next month I wouldn't get to shoot again until November. I drew first relay, so I knew that I would get a good evaluation as to how well this load, and probably these bullets, were going to work in this barrel.
I wound up match champion. I was first in 2 Gun group (six targets), and second in 2 Gun score. I was first in Heavy Gun group with a 2.64 agg, second in light gun group with a 1.96. Those groups are decent for average conditions but aren't exceptional. However, given the guys I was competing with, it is validation that my barrel will shoot the 105 hammers just fine. It isn't a hummer barrel, but it is good enough to compete with.
I have no idea why I abandoned my usual practice of checking the throat after each shooting session. Regardless, the moral of this overly long story is:
Check seating depth after every shooting session!!!!
I started working up a load with H4895 in .2 grain increments and BR-4s. All groups were five shots at 200 yds and measured with my Lab Radar. One load looked promising. I checked the throat and after 45 rounds I had no erosion.
I then shot seating depths from .009 jam to .015 jump. Thought I had my load. It was just under 3/8", 5-shots, 200 yds, ES of 4.
I tested that seating depth with powder increments of .1 grains. The load didn't repeat, so I swapped to Varget and started over. 80 rounds later with Varget and I still had nothing.
So I decided to measure the throat. It had moved .009" in 242 rounds. The chamber on this barrel was the best I had done. When I scoped the barrel after chambering it, the rifling at the throat was crisp and sharp. Also, the chamber diameter was at reamer spec, not enlarged at all. I have known for decades that .005 - .010" of throat movement usually occur within the first 50-100ish rounds as the edges of the rifling round a bit. I have been able to measure that in dozens of rifles. One would think I would have relearned that old lesson going forward, but learning was not yet to take place...........
I had also built my first complete rifle by myself earlier this year, a 300 WSM Light Gun on a BAT B in an LRB stock. I decided that the 300 just wasn't a great choice for 600 yds. While it wasn't bad for 5-shot groups in the LG class, when shooting 10-shot groups in the HG class it just moves too much to shoot it fast enough to stay in condition during a 10-shot string.
So I ordered a .308 BF bolt from BAT B and was going to fit my 6 BRA barrel I had been working with. Turns out headspace and bolt cone clearance were fine, just a little tighter than with the SV, so no machining was required.
I checked the throat with the barrel on the BAT B, recorded that measurement, and went back to load development. As expected, it shot just about the same as it did on the SV. However, I tried an even deeper seating depth and found what seemed to be a node between .013" and .018" jump, but it still wasn't what I wanted.
I wound up discussing all this with @Jet. He suggested I try different primers and brought me some 450s and 400s to try. With the 450s and Varget, it shot a 3/8" 5-shot group at 200 yds, so I thought I had found the load.
The next day or so I visited my friend, gunsmith, and former NBRSA National Champ Curt to check out something on the rifle and get some 450s. While there he showed me how I had a little bit of cock-on-closing, and we were able to fix that by reversing the trigger hanger. In going so we had taken the firing pin fall from about .255 to .235." We talked about how that might require a load adjustment.
So I ran a powder test at that previous seating depth and my load didn't repeat. I went to the range twice that day. I decided the barrel just wasn't going to be a good one. At the match a few days later I didn't even shoot. I went up just to help. I planned to chamber a new barrel and start over for the next match 5 weeks away.
Over the next five weeks I was busy with adding a Single Engine Rating to my CFII, and after that decided to install the DRO on my milling machine before chambering my new barrel. I should have had plenty of time. Of course the DRO took much longer than I had planned, then the Holiday Farm Fire hit and my house was put into Level 1 Evac status (get ready). The smoke was so thick that I couldn't work in my garage.
Well, the smoke finally cleared and the evacuation level was lifted. This meant I could go to the match, but I didn't have a load tuned like I wanted. So I went back and looked hard at my records.
I discovered the best load, shot at the first range session with the 450s, actually wasn't terrible after swapping the trigger hangar. It took .1 grains of powder to shoot a 9/16" 5-shot group at 200 yds. It did shoot worse during my second range session that day (11/16"), but conditions were worse and that was the best I had if I wanted to shoot at the match. Besides, in average conditions it probably wouldn't make a huge difference anyway.
So I prepped all the cases and and then decided I should double check the throat. It had moved another .003". That was enough to move it out of the node. So I adjusted my seating depth and loaded up my rounds.
I told everyone at the match that I had no idea if I was tuned, but since I couldn't make the NBRSA Nationals next month I wouldn't get to shoot again until November. I drew first relay, so I knew that I would get a good evaluation as to how well this load, and probably these bullets, were going to work in this barrel.
I wound up match champion. I was first in 2 Gun group (six targets), and second in 2 Gun score. I was first in Heavy Gun group with a 2.64 agg, second in light gun group with a 1.96. Those groups are decent for average conditions but aren't exceptional. However, given the guys I was competing with, it is validation that my barrel will shoot the 105 hammers just fine. It isn't a hummer barrel, but it is good enough to compete with.
I have no idea why I abandoned my usual practice of checking the throat after each shooting session. Regardless, the moral of this overly long story is:
Check seating depth after every shooting session!!!!
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