462
California's Central Coast Amid The Insanity
At the range, yesterday, I experienced a new-to-me problem.
Qualifiers:
Rifle: 03A3 with a barrel date of 2-43.
Case: Winchester previously fired with RCBS 30-180-SP and 13.5-grains of Unique, then re-sized with a Lee collet neck sizing die.
Bullet: Sierra 165-grain SBT seated with a Forster Ultra Micrometer die to 3.315” for reliable feeding from the magazine. (Sierra’s recommended OAL is 3.330”. Seated to engage the lands, cartridge length is 3.450”.)
Load: 56.0-grains of IMR 4831, though it is of no consequence to the problem. (A picture of two previous 50-yard, three-shot groups attached. Wahoo!! groups for me, considering my screwy vision and issued sights).
Problem:
Eight of the rounds took considerable effort to close the bolt, and I didn’t fire them. The difficulty was akin to seating a cast bullet to engage the lands, only more so. Several rounds required much less effort, and the remaining had the bolt close as if the chamber was empty.
I’ve spent a lot of time measuring various areas of yesterday’s unfired and fired cases, the effortlessly ones, and those that have been full length and small base sized. I can’t find any difference between any of them, other than yesterday’s unfired and fired heads -- measured at that faint ring -- measure .463”, while rounds that chamber effortlessly and full length sized measure .462”, and small base sized measure .461”.
Now, before I see which of the 400-round stash chamber easily, and which ones will have to be torn down and full length/small base sized, does anyone have any idea what is going on, other than an undersize chamber?
Qualifiers:
Rifle: 03A3 with a barrel date of 2-43.
Case: Winchester previously fired with RCBS 30-180-SP and 13.5-grains of Unique, then re-sized with a Lee collet neck sizing die.
Bullet: Sierra 165-grain SBT seated with a Forster Ultra Micrometer die to 3.315” for reliable feeding from the magazine. (Sierra’s recommended OAL is 3.330”. Seated to engage the lands, cartridge length is 3.450”.)
Load: 56.0-grains of IMR 4831, though it is of no consequence to the problem. (A picture of two previous 50-yard, three-shot groups attached. Wahoo!! groups for me, considering my screwy vision and issued sights).
Problem:
Eight of the rounds took considerable effort to close the bolt, and I didn’t fire them. The difficulty was akin to seating a cast bullet to engage the lands, only more so. Several rounds required much less effort, and the remaining had the bolt close as if the chamber was empty.
I’ve spent a lot of time measuring various areas of yesterday’s unfired and fired cases, the effortlessly ones, and those that have been full length and small base sized. I can’t find any difference between any of them, other than yesterday’s unfired and fired heads -- measured at that faint ring -- measure .463”, while rounds that chamber effortlessly and full length sized measure .462”, and small base sized measure .461”.
Now, before I see which of the 400-round stash chamber easily, and which ones will have to be torn down and full length/small base sized, does anyone have any idea what is going on, other than an undersize chamber?
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