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Rifles, Reloading, Optics, Equipment
Reloading
Body sizing? A necessary step?
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<blockquote data-quote="Bart B" data-source="post: 519857" data-attributes="member: 5302"><p>Yes, this is another chapter in the comparison titled "Full Length vs Neck Sizing Only." I think it applies to rimless bottleneck cases, too. The most accurate ammo I know of has all been properly full length sized, both rimless and belted bottleneck cases. Be sure to set the fired case shoulder back no more than a couple thousandths. And don't use an expander ball; RCBS or Redding full bushing dies are excellent. Use a bushing with it's diameter about 2 to 3 thousandths smaller than a loaded round's neck diameter. This virtually eliminates bent case necks often caused by expander balls.</p><p></p><p>Here's an example of what new, unprepped cases and neck turned, weight sorted and flash hole uniformed fired cases will do. .30-.338 Keele cases are made from .300 Win. Mag. cases, looks like a .308 Norma Mag. with a 1/10th inch longer neck. These groups were shot at 1000 yards shooting prone slung up with the fore hand/end on a rice bag and another rice bag under the toe of the stock. My wobble area on the target was a bit less than an inch in diameter from heartbeat bouncing the rifle.</p><p></p><p><img src="http://farm3.static.flickr.com/2633/4198676118_3ab2c51373_m.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>The Sierra 190's were shot from twice fired cases, double sized as I mentioned, neck turned, flash hole uniformed and sorted to a 1-grain weight spread. The Sierra 200's were shot from new, unprepped virgin brass ran through a standard RCBS full length sizing die with its neck lapped out to 2.5 thousandths smaller than a loaded round to set the .300 Win. Mag. shoulder back about a tenth of an inch so the case body's the size of a .338 Win. Mag. Both ammo types had bullet runout of no more than 2 thousandths. The mildest large rifle primer made was used; RWS 5341's. Two sighters were fired, one with each load to center the groups on the target. Then a 190 was fired for its 15-shot group followed by a 200 to its 15-shot group, then back and forth between the two loads for 28 more shots so I could see how each load performed after up to about 30 rounds of each. Note each load's group center is separated by a few inches vertically; the difference between 65 grains under a 190 and 64 under a 200. Compare this test from an old Winchester post '64 Mod. 70 conventionally epoxy bedded in a solid wood stock to the latest whiz-bang pillar bedded wonder used in current day benchrest matches' 15-shot aggregates.</p><p></p><p>Both groups, both with new cases and totally prepped full length sized ones, are about the same size. The chamber is a standard .338 Win. SAAMI speck for case body and shoulder dimensions, but just using a neck long enough for this round. Chamber neck is .344-inch and loaded round neck diameter's .336 for prepped cases, .338 for new ones; lots of clearance around a loaded round's neck. Long live new cases and proper full length sizing. That X-ring's 10 inches in diameter.</p></blockquote><p></p>
[QUOTE="Bart B, post: 519857, member: 5302"] Yes, this is another chapter in the comparison titled "Full Length vs Neck Sizing Only." I think it applies to rimless bottleneck cases, too. The most accurate ammo I know of has all been properly full length sized, both rimless and belted bottleneck cases. Be sure to set the fired case shoulder back no more than a couple thousandths. And don't use an expander ball; RCBS or Redding full bushing dies are excellent. Use a bushing with it's diameter about 2 to 3 thousandths smaller than a loaded round's neck diameter. This virtually eliminates bent case necks often caused by expander balls. Here's an example of what new, unprepped cases and neck turned, weight sorted and flash hole uniformed fired cases will do. .30-.338 Keele cases are made from .300 Win. Mag. cases, looks like a .308 Norma Mag. with a 1/10th inch longer neck. These groups were shot at 1000 yards shooting prone slung up with the fore hand/end on a rice bag and another rice bag under the toe of the stock. My wobble area on the target was a bit less than an inch in diameter from heartbeat bouncing the rifle. [IMG]http://farm3.static.flickr.com/2633/4198676118_3ab2c51373_m.jpg[/IMG] The Sierra 190's were shot from twice fired cases, double sized as I mentioned, neck turned, flash hole uniformed and sorted to a 1-grain weight spread. The Sierra 200's were shot from new, unprepped virgin brass ran through a standard RCBS full length sizing die with its neck lapped out to 2.5 thousandths smaller than a loaded round to set the .300 Win. Mag. shoulder back about a tenth of an inch so the case body's the size of a .338 Win. Mag. Both ammo types had bullet runout of no more than 2 thousandths. The mildest large rifle primer made was used; RWS 5341's. Two sighters were fired, one with each load to center the groups on the target. Then a 190 was fired for its 15-shot group followed by a 200 to its 15-shot group, then back and forth between the two loads for 28 more shots so I could see how each load performed after up to about 30 rounds of each. Note each load's group center is separated by a few inches vertically; the difference between 65 grains under a 190 and 64 under a 200. Compare this test from an old Winchester post '64 Mod. 70 conventionally epoxy bedded in a solid wood stock to the latest whiz-bang pillar bedded wonder used in current day benchrest matches' 15-shot aggregates. Both groups, both with new cases and totally prepped full length sized ones, are about the same size. The chamber is a standard .338 Win. SAAMI speck for case body and shoulder dimensions, but just using a neck long enough for this round. Chamber neck is .344-inch and loaded round neck diameter's .336 for prepped cases, .338 for new ones; lots of clearance around a loaded round's neck. Long live new cases and proper full length sizing. That X-ring's 10 inches in diameter. [/QUOTE]
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