BuffaloBill
Silver $$ Contributor
How could I improve for next time:
I chambered a barrel this past weekend in 6BRA, using a Wheeler #1 spec’d reamer. This was a new reamer. The neck dia per print is 0.268. Attempting to mic across flutes shows maybe 4 tenths over, but was tricky so am not certain. As best I can measure the neck ID in the fresh chamber, using those expanding ball gauges & micrometer, it’s 0.2694. So maybe it cut a thou over(?).
I had initially dialed in the blank at the throat and about 1/4” in from the breech, using Grizzly rod with weight and snug bushing. After drilling out the bulk of material I rechecked runout at the throat reaching in with the 10ths reading Mitutoyo indicator (the one with short stylus and small dia body). This time measuring at the grooves, I made a correction of about 1/10th in one axis and trued the hole, boring it to match the reamer taper. Then proceeded to ream the chamber. I use a PTG floating holder and flush system.
When finished reaming, the reamer seemed to be on-size at the breech. There was no wiggle. Did I likely cause the over size neck because I used the snug bushing on the reamer? I had initially checked runout after dialing in the two locations mentioned above, about 1/2” past the throat, and didn’t see any difference between there and the throat. But admittedly I didn’t measure runout as far ahead of the throat, as the bushing location.
When I view the throat with a Teslong, it looks very well centered. I was very happy with the finish and was patting myself on the back……then found the neck measure a little big.
Do you suspect curvature of the bore ahead of where I checked runout, because of the bushing use, caused this?
I fire formed one new case twice this evening so I could take measurements off it. 1st firing was 29grains Varget, CCI450, 105 Berger Hybrid. 2nd firing was 30grains Varget. Measuring the fired case at the shoulder shows 0.462 (and I assume there would be some spring-back). Reamer print specs 0.461. I assume this is further evidence that the nose of the reamer was being steered by the bushing?
I’d read a number of times from a few of you, that the bushing is to be left out when dialing like I did. I’m wishing now I had done so!
How much sizing at the shoulder is too much? As mentioned above the fired case measures 0.462 at the shoulder. After sizing this case it measures 0.460. This was new Lapua brass.
Here’s pic of twice-fired case. Is it blown out as much as it’s likely to go? I have not trimmed length, and I see what looks like ugly neck turning.
I chambered a barrel this past weekend in 6BRA, using a Wheeler #1 spec’d reamer. This was a new reamer. The neck dia per print is 0.268. Attempting to mic across flutes shows maybe 4 tenths over, but was tricky so am not certain. As best I can measure the neck ID in the fresh chamber, using those expanding ball gauges & micrometer, it’s 0.2694. So maybe it cut a thou over(?).
I had initially dialed in the blank at the throat and about 1/4” in from the breech, using Grizzly rod with weight and snug bushing. After drilling out the bulk of material I rechecked runout at the throat reaching in with the 10ths reading Mitutoyo indicator (the one with short stylus and small dia body). This time measuring at the grooves, I made a correction of about 1/10th in one axis and trued the hole, boring it to match the reamer taper. Then proceeded to ream the chamber. I use a PTG floating holder and flush system.
When finished reaming, the reamer seemed to be on-size at the breech. There was no wiggle. Did I likely cause the over size neck because I used the snug bushing on the reamer? I had initially checked runout after dialing in the two locations mentioned above, about 1/2” past the throat, and didn’t see any difference between there and the throat. But admittedly I didn’t measure runout as far ahead of the throat, as the bushing location.
When I view the throat with a Teslong, it looks very well centered. I was very happy with the finish and was patting myself on the back……then found the neck measure a little big.
Do you suspect curvature of the bore ahead of where I checked runout, because of the bushing use, caused this?
I fire formed one new case twice this evening so I could take measurements off it. 1st firing was 29grains Varget, CCI450, 105 Berger Hybrid. 2nd firing was 30grains Varget. Measuring the fired case at the shoulder shows 0.462 (and I assume there would be some spring-back). Reamer print specs 0.461. I assume this is further evidence that the nose of the reamer was being steered by the bushing?
I’d read a number of times from a few of you, that the bushing is to be left out when dialing like I did. I’m wishing now I had done so!
How much sizing at the shoulder is too much? As mentioned above the fired case measures 0.462 at the shoulder. After sizing this case it measures 0.460. This was new Lapua brass.
Here’s pic of twice-fired case. Is it blown out as much as it’s likely to go? I have not trimmed length, and I see what looks like ugly neck turning.
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