More 5%

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Ross Smith posted this 15 December 2017

When I read about a 5%powder charge variance being OK I was a little skeptical, but I'm coming around. My real concern was in the allowable error of the other components. Since I was having trouble getting my Tikka t3 in .223 to shoot well with hand loads I started weighing brass cases and j-bullets. The results were interesting. So here is the last group of cases that I'm going to weigh. If we sort by headstamp we can easily achieve close enough tolerances in case capacity. All cases were trimmed to length the same , de-primed ,and tumble cleaned. I'm using case weight to indicate case capacity.

PMC brass,.223 had a 3.5% weight variance

LC military mixed lot but recent years, 2.4% weight variance

here's the lulu: 20 different headstamps mixed military and civilian, 10.9% weight variance

Lapua .223 2.0% variance

Hornady cases from their match ammo 6.8%

So what is becoming evident is that 5% is both OK and easily achieved, and if you want to do better that too is easily achieved up to certain point and then consistency becomes ever more difficult.

I hope this adds to the body of knowledge, Ross

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joeb33050 posted this 16 December 2017

Based on experience, reports and experiments; is seems possible that the following variables have little or no affect on accuracy-rifle ctg bench rest:

bullet orientation

case orientation

concentricity of something or other

powder charge variation < 3%?

powder charge wt.

primer pocket uniforming

flash hole deburring

bullet weight variation < +/- .25 gr.

case neck reaming/turning

bench rest equipment

scope cost/quality/power

lube, within some reasonable family

shooter ability beyond some threshold

joe b.

 

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John Alexander posted this 16 December 2017

Joe,

You have given us quite a smorgasbord of things to argue about, many of them long accepted principles for attaining accuracy.

Accepted or not,  I think you are right that we should be very skeptical of most, if not all, of them as something that will improve accuracy.

I should say that because I like to shoot production rifles most all my experiments have been with cast bullet combinations that wouldn't shoot  an honest AVERAGE much below 1 MOA for a string of consecutive  5 shot groups.  So some of these refinements may useful for shooters producing averages near .5 MOA.

On the other hand for shooter, rifle, load, combinations producing 2 MOA or larger averages (most of us) I will give good odds that most of the loading refinements in your list (no matter how long they have been advocated nor how firmly believed) can not be shown by shooting experiments to improve accuracy. 

With the  limitation of average groups above .8 MOA,  I have proven to my own satisfaction by shooting comparisons that it is very hard to show an accuracy improvement with most of the listed refinements.

On the other hand, none of them will probably degrade accuracy. So if you like doing them have at it.  Just don't tell new shooters they need to be done until they're shooting sub minute groups.

John

 

 

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RicinYakima posted this 16 December 2017

Joe and John have convinced me, rationally, that those things contribute little if any to accuracy. But I still do them, cause that is the way I like to reload. Some people drive Chevy's and some drive Mercedes; they all just get you from one place to another.

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45 2.1 posted this 17 December 2017

Knowing what the problem is allows you to formulate a method to solve it. So, just what is the problem? Do you know or just guess? Basically, accuracy results from sending the bullet down the rifle tube concentrically to it's axis..... don't do that and you don't get good accuracy. Accuracy is quantifiable... certain problems give you certain accuracy levels. For an example, undersize bullets loaded well give you about 1.25 to 2 MOA accuracy.

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OU812 posted this 17 December 2017

"concentricity of something or other" ?

A proper fitting concentric bullet (linotype) that is chambered concentric and without binding is very important for great accuracy. 

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joeb33050 posted this 17 December 2017

I can't seem to find experiment results on the relationship between "concentricity" and accuracy. Does concentricity mean that the bullet, case neck and chamber share the same, long, axis? How does one measure concentricity and axis tilt of any of the three? Any help will be greatly appreciated.

Thanks;

joe b. 

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45 2.1 posted this 18 December 2017

"Does concentricity mean that the bullet, case neck and chamber share the same, long, axis?"

In the static sense yes, but dynamic forces change that when the primer fires. Too much slop in fit reduces accuracy. The only practical way to quantify what is right or not is results on the target. Fit figures highly in that. If you shooting 1 MOA or above, you are doing something wrong.

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Starmetal posted this 18 December 2017

Joeb you use a concentricity tool, there are many out there, to measure your loaded cartridge conentricity. Basically  you clamps a loaded cartridge (and it can be a dummy cartridge with no powder) in the device and you turn the cartridge and a dial indicator has a pointer on bullet and you see how much runout it has. The more runout the worse the concentricity is.  Then you work on the reason you have so much runout. Seater dies are a major contributor of this and so are uneven case neck thickness. So you see where turning necks helps things?  I use Forster Benchrest seater dies. In speaking to them they said they use a modified chamber reamer to cut the seater sleeves. They have a bullet diamter section that is very long and seats the bullet pretty straight. Straighter then conventional dies. The seater dies the benchrester use with a arbor press are among the best. The old LEE loaders loades some pretty accurate ammo too. 

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John Carlson posted this 19 December 2017

In his book on rifle accuracy Tony Boyer pointed out that having  the size of the case neck properly matched to the throat of the chamber and a properly sized bullet seated into the lands will guarantee proper bullet alignment when the round is chambered, regardless of it's prior concentricity.  Since we don't have the option of tight neck chambers which we can mate to cases with appropriate neck thickness, it may well be that properly aligning the bullet with the case could be even more productive.  The Hornady concentricity tool also provides the ability to straighten loaded rounds.  Perhaps another idea to test next year but, for now, I have plenty to do with all the projects I thought up to get through the (no shooting weather) winter.

John Carlson. CBA Director of Military Competition.

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OU812 posted this 19 December 2017

A HARD concentric bullet is WAY more important than concentric loaded rounds. You can seat the bullet long so that it aligns itself when chambered (looser neck tension helps do this). 

Softer alloys are more forgiving to being less round, but must be shot at lower velocities. I think faster is better.

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John Alexander posted this 19 December 2017

Ou812,

I think you and Tony Boyer are correct about achiving concentricity. This puts you in some pretty fast company. (It is a little uppity of me to even be casting judgements on Mr. Boyer's pronouncements from on high.)

John is also right that theory that the chamber/neck thickness/bullet provides the concentricity is a little shakier for factory rifles and how most people load them.  However, with a long bore riding bullet seated with not much more than the gas check in the case I think the same principle holds for factory rifles and that's why the 299 type design shoots so well in factory rifles. It applies even more for hard bullets as you point out.

With the kind of bullet design/throating/bumping/tight necks that most of our competitive  shooters use in classes that allow custom rifles (UNR, UNP, Heavy, and PBB) seating the cartridge, or bullet should provide the concentricity -- just as Mr. Boyer says. When this applied it pretty much make concentricity testing of loaded cartridges redundant.

At the other extreme, if the bore, throat, and neck part of the chamber are not concentric or the case neck thickness varies wildly from one side to the other, a perfectly straight loaded cartridge will be bent out of concentricity upon chambering also making the testing of loaded rounds useless.

John 

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joeb33050 posted this 19 December 2017

A certified LEAP to a conclusion.

https://rifleshooter.com/2016/02/rifle-cartridge-concentricity-and-accuracy/

 

joe b.

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joeb33050 posted this 19 December 2017

or, 

http:/.accurateshooter.com/threads/concentricity-impact-on-accuracy.3882060/

joe b.

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Larry Gibson posted this 19 December 2017

A certified LEAP to a conclusion.

https://rifleshooter.com/2016/02/rifle-cartridge-concentricity-and-accuracy/

 

joe b.

Definitely a leap there....more of faith than anything else.  Having shot quite a bit of 7.62 and 308W Russian Brown Bear ammo I would suggest the groups were more a function of the quality of the bullets than anything to do with concentricity.

A test with better quality bullets and a larger group sample (like 10 shots) may have proven the point. 

LMG

 

Concealment is not cover.........

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Larry Gibson posted this 19 December 2017

or, 

http:/.accurateshooter.com/threads/concentricity-impact-on-accuracy.3882060/

joe b.

 

The AMU did considerable ammunition concentricity testing with NM M14s back in the late '60s and early '70s.  They found no discernible difference in accuracy with .000 to .004' concentricity.  With concentricity above that accuracy could be adversely affected, especially at 600 and 100 yards.

 

LMG

Concealment is not cover.........

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RicinYakima posted this 19 December 2017

I'll make one post on this subject, since it has been beaten to death over the last 10 years.

I got involved in this in 2006 when trying to see if different brands or types of reloading dies effected concentricity enough to show up on the target at 100 yards for 10 shot groups. I measured my Mod-Iron Springfield and found that from Cero-safe casts that the chamber was 0.003" off center from the throat and bore to just in front of the web of the case. (1930's Springfield barrels are chambered with 6 different tools, not like the modern practices.)

Cartridges loaded to <.003" all shot the same. Cartridges loaded to >.009" shot worse averages over several ten-shot groups. 

My thought is that if the case presents the bullet into the bore closer to center lines being equal, it will shoot smaller groups over the long haul than bullets farther from equal center lines. It doesn't matter how you do it, but that is what needs to happen. So, I don't think it matters what the gauges shows with the cartridge on the table, as how does it sit in the chamber when the primers lights everything off.

Ric

p.s. This is like measureing powder down to .1 grains or sorting bullets in groups of .1 grains variation: I do it cause it makes me feel good to have 100% control.

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OU812 posted this 20 December 2017

The other day I was fire forming new cases to a barrel that has an excessive over sized chamber. While doing so I was shooting consistent 5 shot bug hole groups measuring under 1/4". I was very surprised to see how easy it was if the rifle and load are matched up correctly. I also shot a grasshopper walking on target...100 yard distance.

Barrel: Brownell's / Shilen short chambered 223 chrome moly barrel, 1/9 twist with "very large" chamber (pressure safety reasons). Finish fitting with 5.56 NATO reamer

Load: Lapua 223 cases, N133 23 grains, Remington 7 1/2 primers, Moly coated Sierra 52 gr Match bullets seated long to contact rifling, Loaded case concentricity under .001 

This load failed to fully fireform cases.

New cases have loose fit and rattle inside this large chamber, so why does or did it shoot so good?

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RicinYakima posted this 20 December 2017

Case doesn't matter; does the bullet line up and fit? Drat, I posted twice. Have to go flog myself with a wet noodle. Ric

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Ross Smith posted this 20 December 2017

I'm with you Ric, I still believe that all these things are additive or what carpenters call accumulative error. I think sloppy reloading will get you sloppy results. Thanks to all who have responded to this, I'm learning. Ross

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Starmetal posted this 20 December 2017

The other day I was fire forming new cases to a barrel that has an excessive over sized chamber. While doing so I was shooting consistent 5 shot bug hole groups measuring under 1/4". I was very surprised to see how easy it was if the rifle and load are matched up correctly. I also shot a grasshopper walking on target...100 yard distance.

Barrel: Brownell's / Shilen short chambered 223 chrome moly barrel, 1/9 twist with "very large" chamber (pressure safety reasons). Finish fitting with 5.56 NATO reamer

Load: Lapua 223 cases, N133 23 grains, Remington 7 1/2 primers, Moly coated Sierra 52 gr Match bullets seated long to contact rifling, Loaded case concentricity under .001 

This load failed to fully fireform cases.

New cases have loose fit and rattle inside this large chamber, so why does or did it shoot so good?

 

Many years ago Sierra (and they aren't the only ones) said there are two ways to size your cases for reloading. One being full length resizing and the other neck sizing only. Of course today we know there are other options.  With that said Sierra said that a full length resized loaded cartrdige lays on the bottom of the chamber being it's not a snug fit like a neck sized only one. They said that if it sets in the same exact place each time and the rifle is held to the same degree of level each time the grouping will be very good. 

I'd say too that your bullet aligned itself especially being jacketed.  This is harder to do with cast. 

 

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