standard deviation and accuracy

[dogone]

Working up a load for my FN 300 WSM; First five shots on the lands gave a 6 1/4 in. group at 400 yards with SD 19. The next five at .02 off lands was a 3 1/2 in. group with 26.2 SD. Bullets were Berger 185 hybrids. I am new to precision shooting but always thought that less SD would be give better groups. A question to those who know is: Are thses SDs high,normal or low? While checking COAL I noticed all the meplats are irregular so next purchase is a meplat trimmer. Thanks in advance.

 

[.284]

So did you have extreme spreads of about 50 fps? If so that's pretty big and will show up when you get further out.
Which powder are you using?
Rl19 and H4831sc work well for me in the 300 wsm. 19 is a bit faster but 4831 had very small sd's.
What kind of scope are you using? 400 yards is getting far enough that a higher magnification scope will help keep your point of aim consistent.
I think the velocity variations will become more evident at about 600ish and further. I would kinda think that there may be other things coming into play with your group sizes before the sd's that you're seeing because I don't believe that the .002 oal difference would give that big of a change. Load up some more and try again to see if you get the same results

Are you measuring the distance to the lands off the bullets ogive or from the tips?

 

[Mystic Precision]

Was it very cold? Maybe the Chronie was not liking being frozen.

Let the paper tell the tale. There is enough error in a Chronie that the data is really a nice point of reference.

Jerry

 

[dthunter]

I use my chrony all the time. But I realise that its just a tool. Low Standard deviations "NORMALLY" mean better accuracy.
But I have seen MANY times where the higher deviations shot the best.
As Jerry said, let the paper tell you what the gun likes.
When I get an accurate load that has a higher S.D. I tend retest it a Couple of times before I move on with it.

I use a chrony to collect data (velocities) to plug into my Isnipe program. This gives me the best chance to use the software at various distances, and still be "on the paper". I shoot each distance with the calculated MOA adjustment, and then make real life adjustments when evaluating the target. I plot the "ACTUAL" adjustments on a paper graph, and later use the "real life" information to adjust my Isnipe data (velocity,BC) to match.
I prefer to use at least 5 or more range points before i stake much value in the trajectory calculations. After the program adjustments have been made, I go out on the next opportunity to retest these figures.

Just a note: if you have one particular range at which the "real life MOA adjustment" doesnt seem to jive with the rest of the trajectory curve, dont worry. The information might be such that a group was fired in a unseen condition (wind) that altered the impact point. This is why I like to use at least 5 points. Just retest it next time to verify the adjustment values.

There are many ways to do this, this is just my way to approach it.
Hope this info helps in some way.

 

[rgwhitman]

As stated by other shooters--regard SD as a tool not as an answer. A load can be very consistant in velocity but not shoot well at all. This is because the bullet design might not be compatible with your rifle, As an example--VLD bullets have long ogives and a boatail which makes them have a high ballistic coeffecient. However they will generally only shoot well in new barrels with nice fresh throats. In my experience they work best if they are just touching the lands to help with allignment. Now once a barrel starts to show some throat erosion the bullet will have to be seated out further . They do not generally care for jumping to the bore. Once the throat gets worn a bit a less effecient design with more bearing surface will work better. The worse the thraot the more benefit comes from a less effecient design but more bearing surface against the bore. As an example in an older well worn 6.5 Swede rifle a 160 round nose flat base may still shoot very well but a spitzer 140 grain boattail may shoot poorly. In this example a 140 Spitzer might show wonderful consitant SD but get out performed by a less effecient bullet having a much higher SD.

 

[BadAsMo]

Wow… unbelievable.
Uh... I don’t agree that it is ever a good idea to accept wide velocity spreads even if it is accurate at close range unless you are only a close range shooter. You have indicated that you are into precision shooting so I assume we are talking about mid to long range. Well at long range a speed variation is equal to vertical dispersion, that means not accurate. You need to examine why you are getting such a wide velocity spread.

Things to look at
1) Powder scale – Need at least 2 decimal place scale – if 1 decimal place we have our first problem. Your powder charge is sloppy. Try using a sample check weight such as a length of hanger wire that weighs equal to your powder charge plus the weight of the pan. Alternate between your load and the wire on your scale several times to be certain the scale is confirming and reconfirming the same number before you accept it.
2) Case weight variation – Have you selected cases that weigh the same for your chrony testing?
3) Fire formed brass – If your cases are not fire formed you will have wider velocity spread than if they are fire formed and neck sized only.
4) Neck Tension – I have always believed that less neck tension is best. The thinking is that a variation of light neck tension is equal to a smaller number than the same percentage of variation on a lot of neck tension.
5) Seating depth – you will have a wider speed fluctuation the more you jump to the lands. I have always found seating close or into the lands reduces velocity spread.
6) Rounds through the barrel – A clean barrel is slow. As copper builds up in the rifling your bullets will go faster. Don’t start chrony testing with a freshly cleaned barrel. It takes at least 10 rounds through a clean barrel to settle down.
7) Barrel heat – barrel should not be dead cold when you start chrony testing or very hot. Best to start when just barely warm to the touch.
8) If you know anyone with a 2 or 3 decimal place scale – try to weight everything there.

You need a load that is BOTH accurate and low SD.

 

[dthunter]

Wow… unbelievable.
Uh... I don’t agree that it is ever a good idea to accept wide velocity spreads even if it is accurate at close range unless you are only a close range shooter. You have indicated that you are into precision shooting so I assume we are talking about mid to long range. Well at long range a speed variation is equal to vertical dispersion, that means not accurate. You need to examine why you are getting such a wide velocity spread.

Things to look at
1) Powder scale – Need at least 2 decimal place scale – if 1 decimal place we have our first problem. Your powder charge is sloppy. Try using a sample check weight such as a length of hanger wire that weighs equal to your powder charge plus the weight of the pan. Alternate between your load and the wire on your scale several times to be certain the scale is confirming and reconfirming the same number before you accept it.
2) Case weight variation – Have you selected cases that weigh the same for your chrony testing?
3) Fire formed brass – If your cases are not fire formed you will have wider velocity spread than if they are fire formed and neck sized only.
4) Neck Tension – I have always believed that less neck tension is best. The thinking is that a variation of light neck tension is equal to a smaller number than the same percentage of variation on a lot of neck tension.
5) Seating depth – you will have a wider speed fluctuation the more you jump to the lands. I have always found seating close or into the lands reduces velocity spread.
6) Rounds through the barrel – A clean barrel is slow. As copper builds up in the rifling your bullets will go faster. Don’t start chrony testing with a freshly cleaned barrel. It takes at least 10 rounds through a clean barrel to settle down.
7) Barrel heat – barrel should not be dead cold when you start chrony testing or very hot. Best to start when just barely warm to the touch.
8) If you know anyone with a 2 or 3 decimal place scale – try to weight everything there.

You need a load that is BOTH accurate and low SD.

No offense, but I dont think you quite understand what we were getting at. As stated above, the crony doesnt nessesarily measure accurately. If a load shoots great, but the chrony indicates that the standard deviation is high, "chances" are the chrony "may" not be giving you an accurate indication of the velocities. Hence why you should allow the paper target to tell you whats right. The crony helps yes, but I dont consider the S.D. it gives me as GOSPEL.
If a load shoots very well at 100, 200, or further, even with an indicated high deviation, I will retest it to confirm its consistantcy. ONLY BY SHOOTING CAN YOU "ACTUALLY" CONFIRM A LOADS POTENTIAL Wether or not the chrony indicates a good S.D. The TARGET is the only part of the equation I DO CONSIDER GOSPEL.

Only after a given load shows consistant accuracy (for me at least three seperate groups), will I stretch it out further than 100 yards. At 500-1000 yards you will definitely see the "Real Life Potential" of a load develop. And if you really want to see the maximum potential of the LOAD AND SHOOTER, shoot out to 1760+ Yards! It can be both a humbling and exhillerating experience!


From the moment of SENDING "it", to the moment of the target RECIEVING "it", nothing else matters!

I love this shooting stuff!
Keep it fun Gunnutz!

 

[ivo]

I would keep playing with seating depth, once you have found your best grouping load, take it out to 800 and 1000 and see what you get. Don't get too bent out of shape about numbers that probably aren't very accurate anyway(especially if you are using a Chrony...Alpha, Beta, Gamma, blah, blah, blah junk).

If you have established a good shooting load at al of your ranges, then chrono it to help yourself get a drop chart started, then confirm your drop chart...done.

 

[BadAsMo]

No offense, but I dont think you quite understand what we were getting at. As stated above, the crony doesnt nessesarily measure accurately. If a load shoots great, but the chrony indicates that the standard deviation is high, "chances" are the chrony "may" not be giving you an accurate indication of the velocities. Hence why you should allow the paper target to tell you whats right. The crony helps yes, but I dont consider the S.D. it gives me as GOSPEL.
If a load shoots very well at 100, 200, or further, even with an indicated high deviation, I will retest it to confirm its consistantcy. ONLY BY SHOOTING CAN YOU "ACTUALLY" CONFIRM A LOADS POTENTIAL Wether or not the chrony indicates a good S.D. The TARGET is the only part of the equation I DO CONSIDER GOSPEL.

Only after a given load shows consistant accuracy (for me at least three seperate groups), will I stretch it out further than 100 yards. At 500-1000 yards you will definitely see the "Real Life Potential" of a load develop. And if you really want to see the maximum potential of the LOAD AND SHOOTER, shoot out to 1760+ Yards! It can be both a humbling and exhillerating experience!


From the moment of SENDING "it", to the moment of the target RECIEVING "it", nothing else matters!

I love this shooting stuff!
Keep it fun Gunnutz!

I know this guy who got lost in the woods for days because he didn’t believe what his compass indicated was north.

If you are getting no verticals at 1760 yards it’s called luck!

Despite the popularity of unsupported comments indicating chronographs are not precise, chances are if you are getting a 50 fps spread on the chrony, you do not have a 2 fps spread.

 

[rnbra-shooter]

Working up a load for my FN 300 WSM; First five shots on the lands gave a 6 1/4 in. group at 400 yards with SD 19. The next five at .02 off lands was a 3 1/2 in. group with 26.2 SD. Bullets were Berger 185 hybrids. I am new to precision shooting but always thought that less SD would be give better groups. A question to those who know is: Are thses SDs high,normal or low? While checking COAL I noticed all the meplats are irregular so next purchase is a meplat trimmer. Thanks in advance.

I assume this is a factory rifle? (i.e. not a custom built target rifle with a $400 match grade barrel)

Smaller SD is better, *but* at short range it has almost no effect on group sizes. So it is not surprising that at 400 yards you are seeing a disconnect between SD and group sizes. I once has a funny load for my target rifle that shot extremely accurately at short and mid ranges but had a lousy SD (25+ fps SD if I recall correctly). At 900m the SD caused it to give the large vertical spreads you expect and which you cannot ever avoid if you are shooting ammo with significant variations in speed from one round to the next. However I shot that ammo, very competitively, at 300m 500y and 600y. At those distances it was able to achieve half-minute vertical spreads in 10-12 shot groups.

Those Berger 185 Hybrids are very good bullets by the way. You will probably be able to get as good results with them as your rifle is able to deliver.

Those SDs are OK for plinking out to 600y. They are not the cause of your larger-than-hoped-for groups.

You ought to be able to achieve SDs quite a bit better than that. Certainly 15fps SDs (for 10+ shots) should be achievable, and possibly even 10fps SDs too.

You did not say what your muzzle velocity was, nor what your powder charge was. If you are not at or near a max load, I would recommend that you seat your bullet .020" off the lands and work your way up to max. There's an excellent chance that you will find both your accuracy and your SDs improve as you go to a hotter load.

I would recommend that you *not* spend any time effort or money on any of the following, until you have gotten SDs better than 15fps and 10-shot group sizes that average 3/4MOA or smaller:
- trimming bullet meplats
- weighing powder charges to nearest 0.1 grains
- weighing bullets
- weighing brass

Carefully thrown powder charges and bullets straight out of the box are able to produce SDs of 15 or less and groups of 0.75MOA or less. Until you get there, your problem is that you are loading the *wrong load*, not that you are not loading a load accurately enough. Concentrate on finding the *right load*, and only once you've found it is it even worth thinking about doing all these higher order small fussy things.

 

[dogone]

Update; I am using a 16 power scope but will put my sightron 24 on tomorrow My Chrony is 35 years old so is probably not top end. I just shot 5 at 3 off the lands and was back to six inches. I will go back to two off and up the charge. I am shooting from a heated room but the chrony is outside so cold may be a factor.
Great advice so far and I will try to use suggestions as soon as possible.

 

[dthunter]

I know this guy who got lost in the woods for days because he didn’t believe what his compass indicated was north.

If you are getting no verticals at 1760 yards it’s called luck!

Despite the popularity of unsupported comments indicating chronographs are not precise, chances are if you are getting a 50 fps spread on the chrony, you do not have a 2 fps spread.

Nope, you really Dont seem to get it! In the interest of obtaining "ACTUAL ACCURACY" any EXPERIENCED shooter will CONFIRM CHRONY INFORMATION.

And of course you have vertical dispersion at 1760, you do at all ranges! its proportional to the loads performance, shooting conditions, and shooter ability. By calling vertical shots at 1760 as luck? I have shot enough to know what is luck and what isnt TRUST ME!

I know that I wont "WASTE MY TIME" on things that have absolutely minimal effect on a loads performance. You had Some good points yes, but waayyy to particular about some things that dont matter. I dont have much trouble shooting at long range because I learned to listen,learn, and logically analyse info shared here, and personal experience. It can be challenging, but thats where it is fun. More than a few of us that have done considerable shooting, and have good advise/experience to share to those who want/need it. And I will gladly look forward to learning more!

 

[BadAsMo]

Nope, you really Dont seem to get it! In the interest of obtaining "ACTUAL ACCURACY" any EXPERIENCED shooter will CONFIRM CHRONY INFORMATION.

And of course you have vertical dispersion at 1760, you do at all ranges! its proportional to the loads performance, shooting conditions, and shooter ability. By calling vertical shots at 1760 as luck? I have shot enough to know what is luck and what isnt TRUST ME!

I know that I wont "WASTE MY TIME" on things that have absolutely minimal effect on a loads performance. You had Some good points yes, but waayyy to particular about some things that dont matter. I dont have much trouble shooting at long range because I learned to listen,learn, and logically analyse info shared here, and personal experience. It can be challenging, but thats where it is fun. More than a few of us that have done considerable shooting, and have good advise/experience to share to those who want/need it. And I will gladly look forward to learning more!

dthunter: Oh, I get it alright. You appear to suffer from high self-esteem.

I understand that your advise is well intended but I can’t abide the propagation of such disinformation.

The way I read your posts you are suggesting that a person should ignore the chronograph if the load flat lines at 1760 yards which never happens. Then you try to double talk your way out of that by admitting there are other reasons for verticals at such a distance. Very good… Now we are getting somewhere. If you shoot at such a great distance that other variables contaminate the purity of the result, there is no way that result can be a reliable indicator of chronograph error.

Yet despite the rationality of the above you try present yourself as one with more experience than I while continuing to defend this silly position.

If I was not clear earlier I am saying that a good load will be both accurate at close range and consistent in velocity over the chronograph. If you prefer good accuracy at short range and ignore significant speed variation you will get vertical dispersion at long range. This is simply mathematical fact.

If you have some secret method that we can all use to validate chronograph error then by all means share it with the group. We are all eager to learn.... AND if you dont mind, I will put it in my book.

 

[dthunter]

Nope, you really, Really dont get it bud!
If the groups are small at 100, but sd is large, the only way you can verify that the load isnt as bad as the crony is indicating is to shoot it at longer ranges. Not nessesarily at 1760. And that is just common scense!
As far as mathematical fact, physics is physics, and never ever stated anything in any of my post that cant be substantiated by physics and others on this site. As far as being arrogant, that isnt me in the least! Any person that knows me will verify that. Now thats cleared up, you need to take a pill! Relax and just "read" the posts! I never gave any information that wasnt consistant to physics.

You seem awful high on yourself as well! But I am sure you are just misunderstood.

I had/have no intention to insult you or anyone, but my experience gained by many years of shooting, and learning/listening has taught me to share what I know to help others. I still have lots to learn as we all do, but that is what keeps my passion going in this field. You apparently dont like having someone point out holes in your posts. Noone does. It is just to create clarity for new shooters.

I hope I havent bruised your feelings!

 

[Rman]

Lots going on, on this thread. Your chrony is junk, and is simply not capable of achieving the results you demand. Accurate ammo should have have an SD of 10 or less. Accurate ammo does not make an accurate rifle. They are related, but obviously different. As mentioned, you need to make sure your loading set up, including your Chronograph, is capable of delivering the results you desire.
Drop me a PM and we can discuss further, if you wish.

R.

 

[BadAsMo]

Nope, you really, Really dont get it bud!
If the groups are small at 100, but sd is large, the only way you can verify that the load isnt as bad as the crony is indicating is to shoot it at longer ranges. Not nessesarily at 1760. And that is just common scense!
As far as mathematical fact, physics is physics, and never ever stated anything in any of my post that cant be substantiated by physics and others on this site. As far as being arrogant, that isnt me in the least! Any person that knows me will verify that. Now thats cleared up, you need to take a pill! Relax and just "read" the posts! I never gave any information that wasnt consistant to physics.

You seem awful high on yourself as well! But I am sure you are just misunderstood.

I had/have no intention to insult you or anyone, but my experience gained by many years of shooting, and learning/listening has taught me to share what I know to help others. I still have lots to learn as we all do, but that is what keeps my passion going in this field. You apparently dont like having someone point out holes in your posts. Noone does. It is just to create clarity for new shooters.

I hope I havent bruised your feelings!

Dthunter Dude, Normally when I encounter a personality such as yourself on a thread I just go away and hope that you do the same. Due to your persistence however I’m going to sit tight and defend my position and do my level best to refrain from attacking you on a personal level.

First of all I would like to make a blanket statement that there are absolutely no holes in my earlier post.

As for the performance of the Chony for example.. their web site states “Every SHOOTING CHRONY® measures the speed of bullets, arrows, shotgun & airgun pellets, paintballs, et cetera, from 30/fps. to 7000/fps. and with better than 99.5% accuracy.” Now perhaps you would like to believe that’s false advertising but I personally have absolutely no grounds to support such a claim based on my own experience. So I personally accept Chrony’s claim as reasonably true to fact.

Aside from Chrony’s claim I would like to explore the concept that you seem to have alluded to (without further explanation) where you can use bullet impact as an indicator to somehow invalidate the speed values produced by the chronograph. Initially you stated that (and I quote) “if you really want to see the maximum potential of the LOAD AND SHOOTER, shoot out to 1760+ Yards!” to which I responded (and I quote) “If you are getting no verticals at 1760 yards it’s called luck!”. Now perhaps I somehow misinterpreted your point which you later admitted “And of course you have vertical dispersion at 1760, you do at all ranges!”

Without going on any further I think we can probably agree there is a certain amount of double talk going on here.

but anyway… I did a little ballistic math purely for entertainment purposes to examine the vertical dispersion that might occur at more reasonable distances to examine if that might be a rational method of validating bullet speed particularly to a greater degree than the chronograph.

I calculated the vertical dispersion that would occur at both 200 and 300 yards given a 50 foot per second change in bullet velocity from 2800 to 2850 feet per second using a 30 caliber Sierra 155 SMK. Now by my calculations (and please feel free to check the numbers if you like) a 50 FPS change would result in a point of impact shift of .34 inches at 200 yards and .85 inches at 300 yards.

My concern with your statement that “cant be substantiated by physics and others on this site” when you examine the vertical shift I calculated is how you… an “EXPERIENCED shooter” can possibly determine with a reasonable degree of certainty that a vertical shift of .17 MOA at 200 yards or .28 MOA at 300 yards is not just not just normal group dispersion? You must have a very nice rifle.;-)

I suspect that a certain person might be quite pleased with verticals of only .17 MOA at 200 yards or .28 MOA at 300 yards and quickly deduce that the 50 FPS variation on the Chrony is the error because no fault is readily visible in such a group.

Now even to produce such a result would require absolutely pristine weather conditions, probably just as a fog began to lift on a day when you just happen to be out shooting. So the practicality in terms of weather for using this method of validation is… let’s say unreliable.

Now this may be purely coincidence but I do know this about my own experience with my chronograph. Somehow or another the chronograph results just happen to improve significantly when I weigh everything on my $1350 Vibra HT 3 decimal place scale from results I get with my (green, you know the name) 1 decimal place scale.

So to summarize my assessment I think we need to put our faith in the hands of the engineers behind the technology used in chronographs and accept the numbers as the best speed indicator we are going to get. Yes of course we will go out and shoot to see how well we can do but I’m cautious about blaming those verticals on my chrony.

I would also like to state that the one thing a handloader controls most by his efforts is the bullet velocity. The barrel may be junk and your groups may be sloppy but if you do your stuff on the loading bench at least your speed can always be consistent.

 

[Rman]

Wow!
That's a lot of blankets in one statement!
The tolerances you have quoted for the Shooting Chrony are under ideal conditions. Just like the kind that are found indoors, with an artificial light source, at room temperatures. Certainly their equipment is capable of recording the tolerances you mentioned, but only under those conditions.
Take it outside, on a cloudy day, and take some shots. Duplicate, exactly the same thing (impossible) on a sunny day, and you'll see way more than .5% of a difference.
I'll make a blanket statement as well. All low dollar light driven chrongraphs are unable to consitantly deliver accurate enough results to prove, or disprove, SD and ultimate velocity numbers. End of story. Flaws in both function and design prevent this.
I'll also not disagree that most shooters at 300 yards, won't be able to judge the .85" error that 50fps provides. This is ultimatly what makes "ladder" testing next to useless.
As for the rest of your post, imagine how much better you could shoot when you couple your $1350 Vibra HT 3 decimal place scale with a chronograph that costs more than $125.

R.

 

[Chinbullco]

Dthunter Dude, Normally when I encounter a personality such as yourself on a thread I just go away and hope that you do the same. Due to your persistence however I’m going to sit tight and defend my position and do my level best to refrain from attacking you on a personal level.

First of all I would like to make a blanket statement that there are absolutely no holes in my earlier post.

As for the performance of the Chony for example.. their web site states “Every SHOOTING CHRONY® measures the speed of bullets, arrows, shotgun & airgun pellets, paintballs, et cetera, from 30/fps. to 7000/fps. and with better than 99.5% accuracy.” Now perhaps you would like to believe that’s false advertising but I personally have absolutely no grounds to support such a claim based on my own experience. So I personally accept Chrony’s claim as reasonably true to fact.

Aside from Chrony’s claim I would like to explore the concept that you seem to have alluded to (without further explanation) where you can use bullet impact as an indicator to somehow invalidate the speed values produced by the chronograph. Initially you stated that (and I quote) “if you really want to see the maximum potential of the LOAD AND SHOOTER, shoot out to 1760+ Yards!” to which I responded (and I quote) “If you are getting no verticals at 1760 yards it’s called luck!”. Now perhaps I somehow misinterpreted your point which you later admitted “And of course you have vertical dispersion at 1760, you do at all ranges!”

Without going on any further I think we can probably agree there is a certain amount of double talk going on here.

but anyway… I did a little ballistic math purely for entertainment purposes to examine the vertical dispersion that might occur at more reasonable distances to examine if that might be a rational method of validating bullet speed particularly to a greater degree than the chronograph.

I calculated the vertical dispersion that would occur at both 200 and 300 yards given a 50 foot per second change in bullet velocity from 2800 to 2850 feet per second using a 30 caliber Sierra 155 SMK. Now by my calculations (and please feel free to check the numbers if you like) a 50 FPS change would result in a point of impact shift of .34 inches at 200 yards and .85 inches at 300 yards.

My concern with your statement that “cant be substantiated by physics and others on this site” when you examine the vertical shift I calculated is how you… an “EXPERIENCED shooter” can possibly determine with a reasonable degree of certainty that a vertical shift of .17 MOA at 200 yards or .28 MOA at 300 yards is not just not just normal group dispersion? You must have a very nice rifle.;-)

I suspect that a certain person might be quite pleased with verticals of only .17 MOA at 200 yards or .28 MOA at 300 yards and quickly deduce that the 50 FPS variation on the Chrony is the error because no fault is readily visible in such a group.

Now even to produce such a result would require absolutely pristine weather conditions, probably just as a fog began to lift on a day when you just happen to be out shooting. So the practicality in terms of weather for using this method of validation is… let’s say unreliable.

Now this may be purely coincidence but I do know this about my own experience with my chronograph. Somehow or another the chronograph results just happen to improve significantly when I weigh everything on my $1350 Vibra HT 3 decimal place scale from results I get with my (green, you know the name) 1 decimal place scale.

So to summarize my assessment I think we need to put our faith in the hands of the engineers behind the technology used in chronographs and accept the numbers as the best speed indicator we are going to get. Yes of course we will go out and shoot to see how well we can do but I’m cautious about blaming those verticals on my chrony.

I would also like to state that the one thing a handloader controls most by his efforts is the bullet velocity. The barrel may be junk and your groups may be sloppy but if you do your stuff on the loading bench at least your speed can always be consistent.

Why would you waste your time arguing with dthunter? You state chrony is accurate to 99.5%, at 3000 fps +/- the error is 30 fps. Account for lighting problems, or bullets that are too shiny, and there's more error. Extreme accuracy is not chronograph dependent. I've been at a one-mile shoot and watched dthunter shoot. Not being able to comprehend what he posted reveals where you're at. Calling him down for stating the truth reveals what you are.

 

[ivo]

Dthunter Dude, Normally when I encounter a personality such as yourself on a thread I just go away and hope that you do the same. Due to your persistence however I’m going to sit tight and defend my position and do my level best to refrain from attacking you on a personal level.

First of all I would like to make a blanket statement that there are absolutely no holes in my earlier post.

As for the performance of the Chony for example.. their web site states “Every SHOOTING CHRONY® measures the speed of bullets, arrows, shotgun & airgun pellets, paintballs, et cetera, from 30/fps. to 7000/fps. and with better than 99.5% accuracy.” Now perhaps you would like to believe that’s false advertising but I personally have absolutely no grounds to support such a claim based on my own experience. So I personally accept Chrony’s claim as reasonably true to fact.

Aside from Chrony’s claim I would like to explore the concept that you seem to have alluded to (without further explanation) where you can use bullet impact as an indicator to somehow invalidate the speed values produced by the chronograph. Initially you stated that (and I quote) “if you really want to see the maximum potential of the LOAD AND SHOOTER, shoot out to 1760+ Yards!” to which I responded (and I quote) “If you are getting no verticals at 1760 yards it’s called luck!”. Now perhaps I somehow misinterpreted your point which you later admitted “And of course you have vertical dispersion at 1760, you do at all ranges!”

Without going on any further I think we can probably agree there is a certain amount of double talk going on here.

but anyway… I did a little ballistic math purely for entertainment purposes to examine the vertical dispersion that might occur at more reasonable distances to examine if that might be a rational method of validating bullet speed particularly to a greater degree than the chronograph.

I calculated the vertical dispersion that would occur at both 200 and 300 yards given a 50 foot per second change in bullet velocity from 2800 to 2850 feet per second using a 30 caliber Sierra 155 SMK. Now by my calculations (and please feel free to check the numbers if you like) a 50 FPS change would result in a point of impact shift of .34 inches at 200 yards and .85 inches at 300 yards.

My concern with your statement that “cant be substantiated by physics and others on this site” when you examine the vertical shift I calculated is how you… an “EXPERIENCED shooter” can possibly determine with a reasonable degree of certainty that a vertical shift of .17 MOA at 200 yards or .28 MOA at 300 yards is not just not just normal group dispersion? You must have a very nice rifle.;-)

I suspect that a certain person might be quite pleased with verticals of only .17 MOA at 200 yards or .28 MOA at 300 yards and quickly deduce that the 50 FPS variation on the Chrony is the error because no fault is readily visible in such a group.

Now even to produce such a result would require absolutely pristine weather conditions, probably just as a fog began to lift on a day when you just happen to be out shooting. So the practicality in terms of weather for using this method of validation is… let’s say unreliable.

Now this may be purely coincidence but I do know this about my own experience with my chronograph. Somehow or another the chronograph results just happen to improve significantly when I weigh everything on my $1350 Vibra HT 3 decimal place scale from results I get with my (green, you know the name) 1 decimal place scale.

So to summarize my assessment I think we need to put our faith in the hands of the engineers behind the technology used in chronographs and accept the numbers as the best speed indicator we are going to get. Yes of course we will go out and shoot to see how well we can do but I’m cautious about blaming those verticals on my chrony.

I would also like to state that the one thing a handloader controls most by his efforts is the bullet velocity. The barrel may be junk and your groups may be sloppy but if you do your stuff on the loading bench at least your speed can always be consistent.

You'll find plenty of people on this site that have had too many inconsistencies with their "Shooting Chronys" and relegated them to paper weights. I am not bashing the brand because they are not alone. Like you stated how your chronograph results impoved once you started weighing on your 3 decimal place scale, my chronograph results impoved when I stopped using a POS Chrony and invested in a real chronograph.

 

[Dogleg]

AND if you dont mind, I will put it in my book

Oh, please do. I'm looking forward to colouring it.