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View Full Version : Should case weight variances be a factor for accuracy?



VaniB
12-31-2007, 10:15 PM
I like to shoot my 20" RRA NM AR15 for accuracy. I've been prepping my cases by trimming the case mouth, reaming the flash hole, uniforming the pockets, and checking case concentricity. I use a Redding bushing sizer die with a Wilson seater die, and I individually weigh each powder charge.

About the only thing I don't do is sort the cases by weight.....and I had just stumbled upon a couple of guys on Midway's feedback boards commenting that they do this.

Frankly, if everything else is uniform and the same, I can't understand how the slight weight difference from one brass case to another will cause the kinetic motion of a fired bullet to travel down the barrel and arrive at the target differently. :confused:

Any enlightenment on this would be appreciated.

steve stanley
01-01-2008, 10:25 AM
I think sorting cases by weight is questionable for benchrest, for what you are doing a total waste of time, but if it makes you feel better about it do it as a big part of this game is in your head anyway. Steve

Boss Hoss 540
01-01-2008, 10:28 AM
Steve-----good put...

David

abintx
01-01-2008, 11:33 AM
carry things to extremes by weighing primers. Is it necessary? I don't think so. Here's a good site for "Some Finer Points" on reloading: http://www.varmintal.com/arelo.htm.

realm-aw
01-01-2008, 12:00 PM
take a look at Gene Beggs post of 12/27- "Weighing Cases & Powder" - there are so many variables.

Gene Beggs
01-01-2008, 12:05 PM
Along this line of thinking, I will never forget a conversation that took place between Perry Morton and Lowell Frei over dinner one evening in Phoenix. I thought I would never recover from the fit of laughter.

Poking fun at the extreme anal nature of benchresters, these two hall of famers were having a great time discussing the importance of primer spinners. (Yeah, can you imagine?) Lowell stated that they had found some of those things out of round by as much as .0002 :eek: :D

I love these guys !

Happy New Year

GeneBeggs

Dick Grosbier
01-01-2008, 12:18 PM
It depends on the quality of the brass in the first place. Todays brass especially Lapua and Norma is generally extremely uniform.

Older military surplus in particular and commercial brass to some extent may vary in weight to some degree. if you are loading for extreme accuracy checking weight can be a useful tool cases with much thicker walls will have less internal capacity and particularly if you are shooting full case loads with same amount of powder each case and they are small cases pressure variations can occur. Even with fine Brass like lapua I weigh it and keep cases of same weight all together. It is like cleaning flash holes or not cleaning or small primers versus large . Benchrest shooting is all about uniformity and technique, many of these little things add up to a good shooting rifle I do what I feel helps.

I will however agree there is far much less need to do something like weigh brass with the fine quality brass we have today.

Dick

Dave Short
01-01-2008, 12:59 PM
Along this line of thinking, I will never forget a conversation that took place between Perry Morton and Lowell Frei over dinner one evening in Phoenix. I thought I would never recover from the fit of laughter.

Poking fun at the extreme anal nature of benchresters, these two hall of famers were having a great time discussing the importance of primer spinners. (Yeah, can you imagine?) Lowell stated that they had found some of those things out of round by as much as .0002 :eek: :D

I love these guys !

Happy New Year

GeneBeggs


We (myself included) probably are doing some things that aren't necessary. I've eliminated a few things, and probably should axe a few more.

The case weighing thing is kind of funny. When I got involved in this craziness in '95, most were weighing brass right from the box, then prepping it. The first thing I noticed was that there were different amounts of material that came off of the mouths and necks when trimmed and turned......sure enough, the case weights were different after all of the work was done. For years after that, I did all of the prep and weighed and segregated into groups by weight afterwards. As time went on, I often found myself short on time, so finally I decided that I was wasting my time weighing cases and stopped all together.

When I started turning case heads for my PPC-bolt-faced 30, I found that there is enough difference in the groove area of the case heads to cause a considerable weight difference, so I now know it is pointless to weigh them for reasons of uniforming capacity. I've always told myself "If I believe it matters, then it does". I've taken a different approach lately, and that is, If I can prove to myself that it is a waste of time, then it really doesn't matter.....and I quit doing it. I don't have the luxury these days of wasting time, motion, and energy. Unless a shooter has every real & meaningful variable in check, he/she doesn't have that luxury either.

Gene, the primer story is funny, but isn't any worse than some of the things I/we've chased over the years. I'm curious; did they discuss the fact that the primers conform to the pocket when pressed in, so the out-of-round condition may be, well..............

-Dave-:)

VaniB
01-01-2008, 09:26 PM
Thanks guys. Sometimes an important reason for doing something can be inadvertently overlooked or not understood, and I knew I could rely on somebody here to alert me about it if that were the story. But, it seems from what you are all saying, my initial instincts were right that measuring case weight is likely more an exercise in futility.....especially so for semi-auto AR15 shooting.

As Dick says, it makes more sense PERHAPS if I was using compressed loads in a bolt action, while engaged in benchrest competition.


Yep, concentricity and alignment of the bullet and case in relation to the bore is one thing........but when some guys suggest doing anal examinations on primers, you know you have to decide for yourself where to draw the line.

goodgrouper
01-01-2008, 11:23 PM
Remember, accuracy is a cummulative thing. .001" here, .025" there. And big things ALWAYS overpower the little things. For instance, if you miss a wind condition that your flags were screaming at you not to shoot, it will certainly nullify any case weight segregation you did on that shot!

So if case segging makes a small difference than it makes a small difference. How small of a group do you want to shoot?

John Kielly
01-02-2008, 12:43 AM
It depends on the quality of the brass in the first place.
I get by by not using brass from manufacturers with lousy quality control.