How would accuracy change if a brass is fired for several times??

Of course when Page was competing from, the late '40s to the early or mid '70s, groups hadn't quite got down to .25 MOA, although he believed it was within reach. But I do recall in "The Accurate Rifle" he wrote of a fellow who repeatedly neck sized right at the range, and watched his groups open up alarmingly, but blamed it on the need to full length resize, where the cause might well have been work hardening the necks of a small number of cartridges. Provided the bolt closes easily on the cartridge, full length resizing is of little benefit to match ammunition. If you carefully keep your brass separated by manufacturer, lot number, and the number of times fired, as serious bench shooters do, work hardening the neck would have less effect on group size than if you shoot mixed brass all dumped into a box waiting to be prepped for the next loading. Theoretically, each piece of brass would work harden to the same degree with each resizing, bullet seating, and firing, but it would never be as uniform as brass that was properly annealed.
 
Neck-sizing can increase brass life with proper care, but is it conducive to greatest accuracy? I am no authority, but I have found that at least partial F/L sizing is required for utmost accuracy. I surmise that it ensures that the cartridge is centred best in the chamber.
 
I have a theory that hard to chamber brass or even brass that takes a bit if resistance to chamber messes with neck tension. I am thinking that the shoulder being squeezed into the chamber puts a squish on the neck and increases neck tension. All fine and dandy if it is a very consistent squeeze and your rifle happens to like more neck tension. Not so handy if it is inconsistent and the rifle does better with less neck tension. Consistency of the squish is the biggest problem in my mind.
 
I also try to anneal down the neck, past the shoulder and into the case body a little bit. That way I hope to get more consistent shoulder bump. Never got scientific and measured it but it seems that I no longer get that odd case that chambers with more resistance than the rest.
 
If the accuracy of your cases gets worse after being fired several times it could be caused by the case not having equal case wall thicknesses around the circumference of the case. This causes the case to warp and become banana shaped, meaning the base of the case is no longer 90 degrees to the axis of the bore causing the bullet to be out of alignment with the bore.

I'm not nuts and making this up and pulling a story out of my backside, the NECO case gauge below describes this condition and it happen to me several times. It is effected by the quality of the brass and made even worse when this low quality brass is fired in larger military chambers. What happens is the case expands more on the thin side of the case when fired and warps, if the case was put on its base the case would lean like the "Leaning tower of Pisa" and the case will have excess runout.

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You will need gauges to find the problem, and the best you can do is FULL LENGTH resize the cases, the late Jim Hull of Sierra bullets testing lab made the following quote.

"I get my best accuracy when my cases fit the chamber like a rat turd in a violin case", meaning he full length resized all of his cases.

Below the full length resized case is held in alignment by the bolt face in the rear and the bullet in the throat, the body of the case is not touching the chamber walls and the bullet has a little "wiggle room" to be self aligning with the bore.

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Below Kevin Thomas of Team Lapua USA talks about full length resizing and his shooting friend the late Jim Hull.

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You need good gauges to sort your brass for thickness and runout, and with these gauges you can easily find these cases and also setup your dies for minimum runout. The Hornady case gauge in the left rear allows you to "bend" warped cases to minimize runout. :)

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The Hornady case gauge in the left rear allows you to "bend" warped cases to minimize runout. :) (Your always going to has some bad brass)

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There is a reason why competitive shooters use Lapua brass and why it has a reputation for quality made cartridge cases.

NOTE: The biggest cause of case neck runout is improperly setup resizing dies that have the expander button locked down off center and pulling the necks off center. f:P:2:
 
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Boomer, my edition of The Accurate Rifle has three single group records for ten shot groups, of .138" at 100 yds. .298" @ 200 yds. and .918" @ 300 meters. Shot in 1969, 1968 and 1957, respectively. Sort of a tad better than .25 MOA.

Aggregates of five, 10 shot groups, in MOA, run .2270, .2496, and .4248, over 100 yds., 200yds. and 300 metres. They were getting it done. These are heavy bench rest rifles, and group sizes degrade as the rifle lightens. It wasn't the ammo, it was the gun technology that kept their sporting rifle accuracy out of the running, although a single record 5 shot, 100 yard group was recorded at less than one tenth of an inch.

These are shot in match conditions, with a clock running, guns going off around you, and no alibis for "flyers." Not too shabby.
 
ykkid said:
Boomer, my edition of The Accurate Rifle has three single group records for ten shot groups, of .138" at 100 yds. .298" @ 200 yds. and .918" @ 300 meters. Shot in 1969, 1968 and 1957, respectively. Sort of a tad better than .25 MOA.

Aggregates of five, 10 shot groups, in MOA, run .2270, .2496, and .4248, over 100 yds., 200yds. and 300 metres. They were getting it done. These are heavy bench rest rifles, and group sizes degrade as the rifle lightens. It wasn't the ammo, it was the gun technology that kept their sporting rifle accuracy out of the running, although a single record 5 shot, 100 yard group was recorded at less than one tenth of an inch.

These are shot in match conditions, with a clock running, guns going off around you, and no alibis for "flyers." Not too shabby.
Click to expand...

Thinking about it, I recall you're correct. My copy of The Accurate Rifle, and my letters from Warren Page, were lost in a house fire some years ago, and that's one of the books I haven't yet replaced. Sounds like its time I did. My memory is good, just a little short.

Biged51, excellent post! Still, I can't help but think that if you use quality uniform brass, that mirrors the chamber it was previously fired in, and that chamber is concentric with the bore of the rifle, it is then easier to align that cartridge with the bore than if it were undersized. As for case life, today's brass seems to fail at the primer pocket long before there is case head separation caused by excessive FL resizing.
 
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Bigedp51, I am off to the wonderweb to see what Mr. Jim Hull's personal standing in NBRA, or IBRs yearly aggregates are. He huffs about not shooting a rifle which won't get him .5 inch, while in the accuracy game, if the best your rifle could do was .3 inch, you would just drive over it with a bulldozer and buy a real one!

I am not a bench rest shooter, and they seem to have fallen out of the popular reportage, but I imagine they still neck size. And, if there was a whisper of a snowball's hope in Hades that F/L sizing would shrink their groups, well, they are the boys who would jump at it!

Page tells an interesting story about himself, wherein he stopped performing almost all of the obsessive case prep steps, although he still uniformed his flash holes at the beginning of the season, and outside neck turned at the same time. But he never cleaned primer pockets, tumbled, or did a bunch of other obsessive things. His yearly aggregate actually improved! But, brought up on old wives tales, and "everybody says" he went back to obsession the next year, because "he felt more confident."

Where would we be without folk lore?
 
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