Help figuring out .223 accuracy discrepancy

[GlockTerrier]

Quote:
Want to know how this spinning bullet flies after being imprinted by the rifle and launched?

Walkalong: Nope.

Real benchresters do not ever check their targets for an evidence where their bullets flight took them - the competion is decided just by reading of windflags... Shooting is optional - after all - everybody has best barrels, actions and bullets, so - what would be the point?...

Learning to read wind flags is much more important.

He-he... Benchresters do know something about bullet flight in the air. Reloaders do want to know even more...

 

[GlockTerrier]

Redneck2:

I didn't elaborate, but in the Handloader article, Barsness used a machine that measured bullet quality. Juenke (sp?) maybe. Don't remember now. Anyway, very minor imperfections made for big differences in accuracy.

Just dropping a box of bullets on a concrete floor from the height of a few feet would affect accuracy.

Was that a hard copy article or is there some online link to it? I'd love to read it...

I also thought that 0.0005" displacements in a soft lead core bullet do not seem too hard to inflict...

 

[disneyd]

disneyd , it would be real interesting if you could test those same loads at different distances to see what happens. (Same scope setting of course). Even comparing them to the 60gr at different ranges. If you were able and/or inclined to.
Would that be asking too much?

Well, I suppose so, much as I hate to go shooting

I just picked up a box of 55 grain VMaxes, which I'll test against the 55 grain FMJ-BTs and see what I discover.

 

[peterotte]

Well, I suppose so, much as I hate to go shooting

Great! disneyd, I'll be waiting to here your findings!

By the way, how do you folks measure runout? I tried measuring in a lathe then in a holder I made. I held the case by the rim then the bullet and measured the case runout and anything I could think of. I could only detect a small runout at the bullet tip. Meaning that I found the loaded case to be quite straight! Or did I?

 

[GlockTerrier]

By the way, how do you folks measure runout? I tried measuring in a lathe then in a holder I made. I held the case by the rim then the bullet and measured the case runout and anything I could think of. I could only detect a small runout at the bullet tip. Meaning that I found the loaded case to be quite straight! Or did I?

Sorry, peterotte - I personally never measured a runout. The idea that geometry measurements may help to estimate imperfections in the bullet having effect during rotation at 300,000 rpm after being fireformed in a more than a foot of a hot steel rifling at 3 speeds of sound just by geometry measurements - always sounded a bit far fetched to me...

But our rifles can actually do that every time to the bullet - no superfast spinning motors required I keep thinking that we should be able to improve our reading of the target paper that could tell us everything we need to know about the bullet and ammo, if we know where to look...

Why, for example, disneyd's 55gr not only dispersed but shoot the whole 1.5" -2" higher group at 100 yards from the rifle that can shoot at the same distance the same hole with supposedly better, but close weight 60gr.... Assuming, of course, that disneyd doesn't just pull our leg and didn't just aimed a bit higher....

 

[Walkalong]

the competion is decided just by reading of windflags...

It is a huge part of it.

everybody has best barrels, actions and bullets

Pretty much. 97% of the rifles/loads on the line are good enough to win. It's the dope pulling the trigger that wins. (while watching the flags )

 

[jpwilly]

My DPMS 20" SS Bull Barrel 1-9 twist will shoot 50-53gr bullets about 1" higher than 60gr bullets. I haven't checked but am sure it has more to do with the velocity difference than the bullet weight. Just got a chronograph but haven't been to the range with it yet. My BBl seems to like the 50gr bullets. I shot some Black Hills Match 69gr and they keyholed at 100yrds!

 

[peterotte]

Interesting, that, jpwilly . I know that it is unpredictable but one usually expects a lighter and faster bullet to shoot lower. It just goes to show what is going on in a rifle. Is the barrel by any chance lower than the 'recoil' axis?

GlockTerrier, you are right. If I had been more alert I might have 'read' that there was something wrong with my hornet. I just blamed the rusty barrel! And then I got thrown off by one or two very tight groups with different bullets but similar POI.

GlockTerrier, I was thinking more of the effects of a bullet entering the bore 'less than perfectly straight' I am doing stuff to keep it in line as much as possible and my recovered bullets seem to indicate a degree of success but I am not quite sure how to quantify this. And of course there is the all important drop test - the range!

 

[GlockTerrier]

I have some of these cannelurred bulk 55gr Hornady's. I also have a bullet comparator (ogive-to-base) that I haven't used yet...

What may be interesting to do is to measure anything we can realistically measure about the bullet consistency: OAL, weight, base-to-ogive - for a sizable sample of bulk and match bullets and compare variances, ranges etc. (Granted, we really need to get a rotational momentum characteristics of the bullet - but even these can be better than nothing. )

He-he... Just wanted to let you know that I was dumb enough actually to waste my time to measure variances of all above factors for two kinds of bullets:

Sierra 52gr MK - and twice as cheap Hornady cannelured 55gr BT-FMJ
The variance/consistency of a three measured factors : weight, OAL, base-to-ogive size - is I think negligible as it is measured in tenths of a percent.

Moreover, much cheaper Hornady 55gr had these miniscule already variances twice lesser than more expensive SMK! []

Although couple of groups don't mean anything - in two 5 shots group (loaded approximately to the similar speed and the same COAL) the best three were the same for SMK and Hornady within 3/4"@100yards from 16" M4gery in semiauto loading mode with Hornady's POI just slightly (0.25") below and to the right from SMK... The biggest difference was with the "unlucky" 2, though My SMK's "flyers" increased 5-shot group just to 1.25". My Hornady unlucky 2 were way off center - about 1-2" to the right and higher... I'm writing these off as just me being a lousy shot - as I don't have any other explanation, since I was shoothing through the chrono...

(But I could swear that my POA at no time was even close to these far away (at 8x scope magnification) points )

I'm convinced now that all these "easy" bullet parameters is a waste of time to measure - as they do not provide any insights into consistency of much more I think important parameter of the spinning bullet in flight - its mass distribution.

So what is a popular wisdom, guys - have you seen "flyers" that suprised you, ones you couldn't "call"? Is this always an "operator error" ? Or can the "flyer" be just a seriuos anomaly in the bullet flight?

 

[taliv]

flyers are exactly that by definition: ones that surprise you and that aren't on call.

what most people call flyers, are actually just the result of a normal group with insufficient sample size.


edit: there's a sticky on arfcom that adequately describes the phenomenon. if you havent' read it, let me know and i'll find a link.

 

[GlockTerrier]

there's a sticky on arfcom that adequately describes the phenomenon. if you havent' read it, let me know and i'll find a link.

Thanks! I'd appreciate that very much!

I think I understand random distrubitions, bell curves, "three sigmas", etc..
I'm just curiuous if there's a sense of relative contrubutions to this "randomness" of various factors in a "typical group" - say, bullet flight anomalies (random shift of POI for fixed POA/launching charachteristics) vs. "bad shooter" factor (random sfift in POA resulting in POI shift)...

 

[peterotte]

there's a sticky on arfcom that adequately describes the phenomenon. if you havent' read it, let me know and i'll find a link.

I would appreciate that too. Thank you!

I fired a few five shot groups and what surprised me was the tendency for there to be 3 shots close together, one a bit further away and a 'flyer' printing high (or sometimes, elsewhere). These were with different bullets and charges. The general POI was similar. (There was some gusty wind but at 100m/110yds)? Unfortunately, I couldn't see the holes so I do not know the order of the strikes.

 

[taliv]

http://arfcom.com/forums/topic.html?b=3&f=118&t=279218

 

[Walkalong]

what most people call flyers, are actually just the result of a normal group with insufficient sample size

Usually just a misplaced shot, called or not.

Sometimes there are unexplained "fliers" which experienced rifle shooters can differentiate from a missed shot.

 

[GlockTerrier]

http://arfcom.com/forums/topic.html?b=3&f=118&t=279218

Thank you very much, taliv!

There was not a whole lot of a new or interesting information for me wrt statistical group measurements, my college professors many years ago made sure that I never forget such basics

However, I found a quote there from Rick Jamison who actually built and used a "machine rest" to exclude a shift in POA due to an "operator error" that was exactly what I was looking for:

There are stories of a single bullet that for no explained reason flies out of what might have been a tight cluster. This often occurs with a three-shot string and many times with a five-shot string. If you're lucky enough to fire a group without a flier, you can end up with a very tight group. However, usually what happens if another five or seven shots are fired to complete a 10-shot string, other bullets fill in the space between the main group and the flier to make a reasonably rounded group. Ten shots are a more reliable indicator when it comes to predicting what a load is likely to do in the future.

The problem with 10-shot groups is that when you report them, everyone thinks you aren't shooting very well or that the ammunition is not good because the group sizes are so much larger than three- or five-shot groups. Also, when we're firing three- or five-shot groups with a flier, it is only natural to assume that it was caused by a flinch or "pulling" the shot. Therefore, since the flier was our own fault, the tendency is to eliminate it from any reporting of group size.

This is one of the advantages of using a machine rest... The machine rest reduces the human element.
After using this machine rest for several years, I have determined that a 1.5-inch 10-shot group at 100 yards... is a good one.

If which case a "flyer" can still be most often exactly that, after all - a deviation of a bullet in flight...

 

[GlockTerrier]

Usually just a misplaced shot, called or not.

Never doubt your word, Your Honour - but out of sheer curiousity - how do you know that?

 

[taliv]

you're welcome. yeah, the article wasn't very technical, and it's maybe a little overbearing/insulting. but, that's arfcom for you.

If which case a "flyer" can still be most often exactly that, after all - a deviation of a bullet in flight...

i don't understand your point. it's not ANY deviation. it's an unexplained deviation. if i pull a shot or jerk the trigger, that's not a flyer. it's a bad shot.

really, a flyer is just something outside your normal group that's not accounted for.

the point of that link is that if you eliminate as many of those human factors as possible and shoot sufficient sample size, most people's rifle/ammo combo are going to be doing good to achieve 1.5 inch groups. it's not flyers that make it a 1.5 inch group. flyers are outside that.


imho, bonafide flyers are probably due to things like a small, off-center bubble in the bullet core, or the bullet having been seated crooked, and me too lazy to weigh/check runout. or maybe something caused the last bullet to leave a little extra piece of copper fouling in the barrel and that affects my next shot. who knows?

 

[peterotte]

Thanks for that taliv. To illustrate that point exactly, you can have a look over at this link to see my 3 shot groups .
http://www.opticstalk.com/forum_posts.asp?TID=8183&PN=1&TPN=4
Next, I'll be posting the full five shot groups - including the 'flyers'

 

[GlockTerrier]

i don't understand your point. it's not ANY deviation. it's an unexplained deviation.

I think the rest of your post tells me that you've got my point pretty good.

Only "machine rest" or other some like contraption is capable to eliminate "human factor". Nothing else. Note that 1.5" out of 10(!) from "machine rest" is a good(!) group in 100 yards.

And if you waded through the statistics portion of the thread you'd agree that if your one "good" 10 shot group is 1.5", your "bad" 10 shot group can be 4.5" - from the machine rest. No human error invoved.

Assuming that launching platform and ammo loading characteristics and components are nearly identical - only bullet flight properties would be different. I call it a "flyer"

 

[peterotte]

'Flyers' would be an impact that is obviously and substantially out of place in a ten shot string. They could indicate muzzle wear or throat erosion. You guys actually bring up an interesting and very relevant point here. That is strike probability. Wouldn't it be better to quote accuracy in terms of how many out of ten shots would fall within MOA? Say, 75% MOA, 90% 1.5 MOA, 100% 2 MOA. That means that at worst, my shot will fall within 4" @ 200yds but 75% of my shots will be within 2". Make any sense?

I used to use the three shot group for sighting in purposes. I knew my rifle would print a certain 10 shot group size. So, to adjust my sights, I would fire a three shot group, assuming that the spread would represent the group. If those three grouped too close together, I knew I had not found the mean group centre - but only because I knew the 10 shot group size. To me, that's and accurate rifle. One that shoots a three shot group that represents the mean. (Funny thing - I found 1.5 MOA 10 shot string, to be a good group too. From a machine rest, that is. But my 303 did better, with 50mm at 200m – at least, I think that is better. At that distance, I could hit a beer can).

 

[GlockTerrier]

Wouldn't it be better to quote accuracy in terms of how many out of ten shots would fall within MOA? Say, 75% MOA, 90% 1.5 MOA, 100% 2 MOA. That means that at worst, my shot will fall within 4" @ 200yds but 75% of my shots will be within 2". Make any sense?

Makes perfect sense to me, peterotte! In fact you've just formulated pretty much a definition of a probabilty distribution function from statistics... I keep this type of description in my head as an aggregate description of my accuracy - like, at this distance with this ammo I can hit this area this number of times out of that on average.... Helps to plan ammunition count required to hit the target

The question for a reloader is what do we do in the absence of the "machine rest" contraption to separate ammo/rifle issues from the "human factor? If once in a 30 shots the ammo can fly 4.5" off the POA even from a machine rest - whose fault this 4" flyer is on this specific 3, 5, 10, 30 shot group? Given two types of ammunition and no "machine rest" how soon can we tell with a confidence that one is better than the other?

 

[peterotte]

Good point GlockTerrier . My problem as I see it is to find out what might have caused a flyer so as to eliminate that cause. That's what makes it fun - and frustrating! I shot a few groups of five of different loadings this weekend past and found a tendency for the rifle to print three very close, one a bit off, and another way off high. Does that mean I have a crap rifle or is there some inconsistency with my loads? Only one way to find out - keep trying! The only thing I am sure of is that those bad shots were not me.

By the way, I concluded on the machine rest thing that I can shoot as well without one, from a bench so gave up on it. (I even had a little hydraulic trigger device to fire it).

 

[Walkalong]

tendency for the rifle to print three very close, one a bit off, and another way off high

Shoulder, breeze switching and blowing towards the target, bedding, you.

It is consistent, so I would not call it a flier. It is not unexplainable, just not diagnosed yet.

I think we define "flier" differently. Most "fliers" are not fliers by my way of thinking. It is not a statistical anomoly, it is an occasional unexplainable random shot away from the statistical group.

 

[GlockTerrier]

I concluded on the machine rest thing that I can shoot as well without one, from a bench so gave up on it. (I even had a little hydraulic trigger device to fire it).

Peterotte, with all respect, I think you had probably a very solid but still a shooting rest for your rifle... It greatly diminished but did not exclude completely POA variability from shot to shot. But have you seen Ricks' "machine rest" contraption ? It is no rifle anymore - it is some kind of action merged on a massive platform, pretty much just a lunching platform for bullets:



If THIS thing calls 1.5"@100y in 10 shots a "good" group, this statistically means that you have a decent chance to a 4.5" miss when shooting several 10 shot groups - due to a variance in bullet flight trajectory alone!

No wonder that you shoot as good w/o the rest as with it - it can easily be explained if your error contribution to "flyers" is probably less than variance of bullet trajectories due to variance in bullet/ammo properties and their interaction with environment in flight - wind, etc.

 

[GlockTerrier]

I think we define "flier" differently. Most "fliers" are not fliers by my way of thinking. It is not a statistical anomoly, it is an occasional unexplainable random shot away from the statistical group.

Walkalong, naughty you, you're on the verge of crossing into philosophical porn about scientific method, randomness, determinism, etc. Out of all people here...

Statistics as method comes into play when gazzilion of physical factors that deterministically define every individual outcome - are all lumped together, so instead of attempting predicting inidvidual outcome we're content to describe the approximate behavior of the large group of observations influnced by the same gazillion factors (averages, deviations and other such properties)

Here you have it - if you have a statistical method, you're NOT interested in explanations of every individual observation by definition. You're mostly studying properties of large collections of these observations and how these aggregate properties may statistically correlate with a few selected factors.

But if your looking for an explanation why this specific hole punched 4" off center - statistics (group sizes, etc) are meaningless. You're right into detailed examination of the physics and laws of the phenomen you study....

So depending on the method a "flyer" is just a sample from a "tail" of a random distribution. Or it is an interesting trajectory of a specific bullet flight that takes it farther way from a theoretical/expected POI for the same POA and other initial flight charcteristics as the other bullets - that we're trying to explain away.