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sorting brass and bullet data for best accuracy

 
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  #1  
Old 09-01-2012, 11:14 AM
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Join Date: Mar 2012
Posts: 10
sorting brass and bullet data for best accuracy

Hi all,

I have been getting deep into reloading, I have a tendency to embrace things with gusto or not embrace them at all, this is no exception. First off, I realize that there is such a thing as overkill, especially without a custom rifle (I have a new 700 5R) but I enjoy the pursuit of excellence for just that, the pursuit J

To date I have manages to get my reloading down well enough that I average 0.52 MOA at 300 yards (on average over last few hundred rounds). I have spend a lot of time and a lot of money on equipment (a lot for me anyway)
I have a very accurate glass enclosed scale that gets me to 0.02 grains, I have competition dies, a Redding instant indicator, a run out gauge/corrector (Hornady), Wilson seating die with arbor press. I practice as consistent a reloading process as I can. I sort bullets (weight and base to ogive). Each case is measured from base to Datum (DL) length as well as volume with 99% iso-alcohol (I have a neat item I made to allow this to be done with a deprimed, cleaned and reedy to go case, will add pic)

I hand turn the case neck thickness on each case, polish the inside case neck wall, deburr with 0000 steel wool Then ultrasonically clean each case, all after the obligatory vibratory tumble and primer pocket uniforming and deburring. I measure case wall expansion after seating as well as pressure needed to seat the bullet

I use:
Lapua Brass
CCI-BR2 primer
Varget
SMK 168 HPBT

My question is this. At the end of the process I have a lot of data. When I select the bullets and cases to match together, what would you find folks say is best sort order to use in properly grouping cases and bullets for consistent groupings.

My thinking is that these two are most important
1. Base to DATUM
2. Case volume

I donít think that case weight is that important since I measure volume, my cases are all same COL (+/-0.001)

As far as bullets, I think the Base to Ogive is most important then weight (SMK is very consistent, I just look for the occasional, rare, outlier)

Any suggestions on how to best group the data so that like bullets, cases and eventually rounds, are near each other when I go to the range

Thanks all

BTW, I just started doing this in May, like I said, I have embraced this with a fair amount of seriousness.

All the best

John
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  #2  
Old 09-01-2012, 04:50 PM
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Join Date: Oct 2010
Posts: 86
Re: sorting brass and bullet data for best accuracy

i am in awe. been reloading for hunting purposes for nearly 30 years, and i don't know of anyone, much less myself, who goes thru these steps. I typically am pleased with 1" groups at 200 t0 250 yrds. that should equate, plus or minus wind drift and angular deflection to about 2-1/2" to 4" at 500 yds. Hell, i can't see futher than that any longer.at these ranges length of base to ogive seem to be the leading indicator when all else is equal. Do an experiment tho with the SMK's - check the OD tolerances at several points on the body and at several angles. Sometimes they will have some that fail to meet my expectations of good - +/- 0.001". Has to be something in the condition of the swage/form die during that cycle of umpty thousands of rounds.Congratulations and adulation.
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  #3  
Old 09-01-2012, 05:33 PM
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Join Date: Mar 2012
Posts: 10
Re: sorting brass and bullet data for best accuracy

Well, I would be in awe as well if I was 0.52 MOA at 500 yards, I have never been at a range that allows that (being stuff in "gun friendly" NJ)

I want to compete in F-class someday and feel these reloading habits will pay off then

JC
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Old 09-01-2012, 07:44 PM
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Join Date: Mar 2008
Location: SD
Posts: 252
Re: sorting brass and bullet data for best accuracy

Does anybody know anything about or if Neco Quickload program would help Offgridkid. It looks kinda neat but I don't have any experience with it.

Also if you get into F-class those sinclair bipods look cool.
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  #5  
Old 09-01-2012, 07:49 PM
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Join Date: May 2012
Location: N.D.
Posts: 2,616
Re: sorting brass and bullet data for best accuracy

There are things that make a difference and things that take up time. The bullet and barrel liking each other is about 90% of accuracy. Uniforming your brass helps, but you are using a factory barrel with the generous chamber that it comes with so some things like neck turning are actually somewhat detrimental for accuracy. With a factory chamber anything over knocking off the high spots is to much as your neck fit gets sloppy in the chamber. I don't even bother turning necks in my custom barreled m700 lh 7stw.
Nearly every one of my rifles is capable of moa or better over the long haul. The ones that aren't are over 30 cal. I'm still sorting out the 270 my wife got me for christmas last year. I think I'm there but haven't really got it proved yet.
Weighing your powder can help, but a lot of br shooters simply dump charge reloads with powders that at best are .1 grain accurate on average.
Brass and bullets to 1% total variance or less on weight is good.

you said you measure seating pressure, but do you cull those out of a certain range?? The uniformity matters more than the actual pressure.
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  #6  
Old 09-01-2012, 07:56 PM
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Join Date: Jan 2005
Location: OK
Posts: 2,145
Re: sorting brass and bullet data for best accuracy

I have tried many things and came to the conclusion that there are a few that make a measurable difference.

1. The one BIGGEST accuracy improvement you can make is to tune your load into the center of a large accuracy window.

Thus if your a tenth of a grain light or heavy, on powder charge, it makes little to no difference in vertical. (I consider .1 grains above or below my target weight acceptable with cases that hold over 65 grains of powder, I shoot for .05 grains on smaller charged cases.)

And if your bullets vary in length, bearing surface by a couple thou, your at a sufficient bullet jump that it doesn't have a negative impact.

2. Brass prep/sorting will garner the biggest improvement if your looking for something to sort.

This would include any process that makes your brass consistent including annealing.

At one time I sorted bullets, in general match grade target bullets from the manf. are so close I deemed it unnecessary and my scores didn't improve when I did it.

Bullet tipping may give you a slight balistic advantage, and a little more consistency, if done properly, but some bullets 6mm and 6.5mm I refuse to mess with. I have done the 180 berger and 175 smks. But as of late been skipping the process, seems when un-altered bullets hold 1/2moa vertical at 1000 yards it is almost pointless.

Loaded round concentricity, I seat the bullet half way and back out turn the case between 90- 140 degrees and seat the rest of the way. I never measure them because i wouldn't care to think about how little it would actually matter if they ran out 1-2 thou.

Amazingly enough I win and place pretty high in all the matches I shoot, when many of the guys below me fiddle around with there loading way more than I do.
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  #7  
Old 09-01-2012, 08:04 PM
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Join Date: Dec 2005
Posts: 2,113
Re: sorting brass and bullet data for best accuracy

All the prep and measure stuff I've done over the years with .308's and a couple of 30 caliber magnums is rather skimpy. But it's worked to produce no worse than sub 5/8 MOA accuracy with 20+ shot groups through 1000 yards.

Cases; weigh 20 and get the average. Turn the necks on those with more than .001 inch spread in wall thickness. Then weigh all of them putting those +/- .75% of the average (a 1.5% weight spread) in one group; about 2/3rds of the cases will usually be in this middle group. The lighter ones in a "lite" group and the heavier ones in the "heavy" group. Then keep each group separate for shooting and reloading. While some folks sort by case capacity, I've done that and found it's no better than sorting by weight and a lot less time, mess and cleanup. Forget primer pocket and flash hole prepping; there's a bigger spread in primer pellet heat and pressure output than making the flame have an easier path to the powder.

Bullets, get good ones then shoot 'em. Sierra and Berger match bullets are excellent. Sorting by weight's the least important; 1/2 grain difference is insignificant in what change in BC that'll have. Sorting by some dimension's a waste of time, too. Been there, done that and all without benefit. Unless you can spin bullets at 30 thousand rpm and measure their unbalance sorting out those that don't fly out of the collet holding them and are the best balanced. I don't think it's worth measuring and weighing bulets.

Powder, for ranges 300 yards and less, meter powder directly into the case. Practice so the charge weight spread is no more than .3 grain; 3/10ths grain. For longer ranges, weigh powder to a 1/10th grain spread; 0.1 grain. There's more spread in the chemistry of exact charge weights that cause different shaped pressure curves and peak pressure than what a 1/10th grain difference in powder will cause. Use medium speed powders; not those slow ones that give high velocity with big spreads. Stay far, far away from ball powder.

Primers, milder ones tend to give better accuracy. But the Wolff standard and magnum primers are very uniform and are the favorite of most high power competitors.

Finished round, bullet runout not to exceed .003 inch. Most any seating die will make straight ammo if the case neck's straight and well aligned with the shoulder and case axis. I prefere to seat bullets for best accuracy touching the lands; seated several thousandths long in case necks with just enough tension to hold them in handling and loading. This lets the bullet seat back when the round's chambered and have the same jump distance and start up resistance for every shot. As the head to shoulder length of sized cases have a small dimensional spread, getting the same distance from case head to some diameter on the seated bullet ends up with different jump to the lands distance.
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