I've been chasing some accuracy issues with my 6.5x47 match rifle. Was thinking the barrel was going out at only ~ 1900 rounds, THEN I pushed a bullet down the neck of a fired case and had it abruptly stop at the neck shoulder junction. No way I could push it hard enough by hand to get past the donut. Tried it with all of my fired cases, including the ones that were only fired 2X; the same result every time.
A bit of background:
I bought this rifle used at the end of January, with a reported 140 rounds down the tube. A borescope inspection confirmed the round count was low, as the throat and bore looked brand new. Right out the gate, the rifle was a laser, with 0.2 - 0.4 MOA groups being the norm. It's a North West Precision action (re-brander Stiller?), Bartlein 1:8 twist barrel. The chamber was cut with a no-turn reamer and a rather short throat (0.050" freebore), which makes seating heavy bullets ahead of the donut mostly impossible. So far of the bullets I've tried, only the 130 AR Hybrids will seat in front of the donut. I don't and do not want to turn necks. I'm using a Forester Bench Rest Full Length resizing die, initially with the expander ball, but removed it for producing too much runout (maybe related to the donuts?), and now use the die without the expander ball. I expand the necks in a second step with a Sinclair expanding mandrel.
I've been bumping shoulders during the FL sizing process with this cartridge ~ 0.002" - 0.003" (more than I usually do with other cartridges), only because with a 0.001" - 0.0015" bump I was still getting a hard bolt close. At 0.002" shoulder bump I could feel some slight drag when closing the bolt and at 0.0025"+ shoulder bump, the bolt closes smoothly. Bump measured with a Hornady Lock-&-Load bump gauge.
So far, I've annealed the brass on every-other firing and question whether the annealing is contributing to the donut formation (softening the brass in the shoulder/neck area, allowing it to flow more freely?). I've also experienced donut issues with a 338 Lapua where I was annealing on every firing.
Anyway, once finding the donuts, I dug out my Wilson 6.5mm custom inside reamer that I had made for a 260 Remington with a slight donut issue. It fit the 6.5x47 Lapua perfectly, removing the donut without touching the rest of the neck. After reaming, the bullets would slide down the neck without any noticeable drag on the neck-shoulder junction. On the reamed brass, sizing effort with the expander mandrel was noticeably lessened, concentricity improved, seating effort was less and more consistent, and, of course, accuracy improved. I also tried using the 130 AR Hybrids on un-reamed brass with the bullet bearing surface seated ahead of the donut. This also produced good/improved accuracy.
Another detail; on the brass that I reamed, loaded, and fired, the donut came back again immediately. As in, a bullet would not slide past the neck/shoulder junction on fired brass that was just reamed the previous cycle.
I mostly posted this to be informative, but do have some questions:
1) Is it common to get donuts with the 6.5x47 L cartridge with the 30* shoulder? I've read a lot about donuts in the 260 R and other calibers with 20* shoulders, but not in the 30* shoulder calibers.
2) Is there something that I am doing in the reloading process to cause the donuts? Or something that I should change to eliminate them?
3) Is it normal to have the donut come back this quickly on reamed brass?
4) I was thinking of just running the 130 AR Hybrids, despite the hefty price tag compared with the Norma Golden Targets that I'm currently using and ignoring the donut. But unless I continue to ream the donut at each reloading cycle, I still get increased run-out during sizing, I suspect due to passing the expander ball (or expander mandrel) through the donut. So would switching to a bushing die without an expander ball be a valid solution?
5) When I re-chamber/re-barrel (6.5x47 again) is there a specific reamer I should request to minimize this? Obviously, I'll go with more freebore to be able to run most/all bullet options in front of potential donuts. Any recommendations on what freebore I should specify? Considering using 140 Hybrids or 130 Golden Targets for match loads and 143 ELD-X for hunting, possibly trying the 147 ELD-M's.
A bit of background:
I bought this rifle used at the end of January, with a reported 140 rounds down the tube. A borescope inspection confirmed the round count was low, as the throat and bore looked brand new. Right out the gate, the rifle was a laser, with 0.2 - 0.4 MOA groups being the norm. It's a North West Precision action (re-brander Stiller?), Bartlein 1:8 twist barrel. The chamber was cut with a no-turn reamer and a rather short throat (0.050" freebore), which makes seating heavy bullets ahead of the donut mostly impossible. So far of the bullets I've tried, only the 130 AR Hybrids will seat in front of the donut. I don't and do not want to turn necks. I'm using a Forester Bench Rest Full Length resizing die, initially with the expander ball, but removed it for producing too much runout (maybe related to the donuts?), and now use the die without the expander ball. I expand the necks in a second step with a Sinclair expanding mandrel.
I've been bumping shoulders during the FL sizing process with this cartridge ~ 0.002" - 0.003" (more than I usually do with other cartridges), only because with a 0.001" - 0.0015" bump I was still getting a hard bolt close. At 0.002" shoulder bump I could feel some slight drag when closing the bolt and at 0.0025"+ shoulder bump, the bolt closes smoothly. Bump measured with a Hornady Lock-&-Load bump gauge.
So far, I've annealed the brass on every-other firing and question whether the annealing is contributing to the donut formation (softening the brass in the shoulder/neck area, allowing it to flow more freely?). I've also experienced donut issues with a 338 Lapua where I was annealing on every firing.
Anyway, once finding the donuts, I dug out my Wilson 6.5mm custom inside reamer that I had made for a 260 Remington with a slight donut issue. It fit the 6.5x47 Lapua perfectly, removing the donut without touching the rest of the neck. After reaming, the bullets would slide down the neck without any noticeable drag on the neck-shoulder junction. On the reamed brass, sizing effort with the expander mandrel was noticeably lessened, concentricity improved, seating effort was less and more consistent, and, of course, accuracy improved. I also tried using the 130 AR Hybrids on un-reamed brass with the bullet bearing surface seated ahead of the donut. This also produced good/improved accuracy.
Another detail; on the brass that I reamed, loaded, and fired, the donut came back again immediately. As in, a bullet would not slide past the neck/shoulder junction on fired brass that was just reamed the previous cycle.
I mostly posted this to be informative, but do have some questions:
1) Is it common to get donuts with the 6.5x47 L cartridge with the 30* shoulder? I've read a lot about donuts in the 260 R and other calibers with 20* shoulders, but not in the 30* shoulder calibers.
2) Is there something that I am doing in the reloading process to cause the donuts? Or something that I should change to eliminate them?
3) Is it normal to have the donut come back this quickly on reamed brass?
4) I was thinking of just running the 130 AR Hybrids, despite the hefty price tag compared with the Norma Golden Targets that I'm currently using and ignoring the donut. But unless I continue to ream the donut at each reloading cycle, I still get increased run-out during sizing, I suspect due to passing the expander ball (or expander mandrel) through the donut. So would switching to a bushing die without an expander ball be a valid solution?
5) When I re-chamber/re-barrel (6.5x47 again) is there a specific reamer I should request to minimize this? Obviously, I'll go with more freebore to be able to run most/all bullet options in front of potential donuts. Any recommendations on what freebore I should specify? Considering using 140 Hybrids or 130 Golden Targets for match loads and 143 ELD-X for hunting, possibly trying the 147 ELD-M's.
