More to ammo behaviour than MV?

[grauhanen]

Over the winter I bought a chronograph that can be paired to a smartphone. I decided to take out the Pro Chrono for the first time today because my missus wanted to go to the club property to do some photography. I've used a chronograph in the past, but rarely use my phone, and since my wife is quite familiar with them I thought her presence might be helpful to me. It was also very calm this morning, and it still is as I type.

I did some shooting sans chronograph while my better half took pictures. When she finished I set up the chrony. Once the phone was turned on and the app opened, it paired immediately. As a preliminary test, I shot a over half a box of ammo over the chrony with my 1411. The thing worked as it should. For my more serious test, I used a box of Center X from two years ago. It isn't a very consistent lot, but I was more interested in how what appeared on the target related to what the chronograph said.

Over 50 rounds, the average MV was 1034 fps, the ES was 39 fps, and the SD was 8 fps. No surprises there.

On the target, however, there wasn't always an obvious relationship between POI and MV. Below is the target shot with the CX. While many groups are cringeworthy, groups 2 - 7 (each row shot left to right, top first) were much better than I remembered about the performance of this ammo. Those six groups averaged just under .270".

More important and significant to me, however, was what the apparent incongruity between what the chronograph told me and where some of the rounds impacted on the target. I've appended some notes on the target.

On the first group (top, left side) the shot with the lowest POI had the highest MV of the five shot group. On the ninth group (second from right side, bottom row) the shot with the highest POI had the lowest MV of the group.

To be sure, the further the target the target the more MV variation should be seen on targets. At the distance this target was shot (57 yards), a difference of 10 fps between two rounds should result in a vertical spread of about 0.1". At 100 yards, similar rounds with the MVs I had today would have about .29" of vertical spread.

I understand that one target and one set of chronograph data is a limited amount of data. I thought it was curious, however, that the conventional wisdom that rounds with a higher MV will strike the target at a higher POI than those with a significantly slower MV. It suggests, but clearly not prove, that there's more to ammo behaviour than MV.

 

[TheWhole9Yards]

Very interesting!

 

[kjohn]

Interesting, indeed! Thanks for sharing.

 

[emerson]

Very interesting. I wonder if it’s barrel harmonics that impact vertical stringing even more than mv. Considering barrel dwell time Rimfire vs centerfire, it could be a bigger impact on the slower Rimfire projectile. There are a few folks experimenting with 1:12 that seem to have much less vertical stringing at extended range, but with so many variables it’s hard to say.

 

[RabidM4U5]

Very interesting. I wonder if it’s barrel harmonics that impact vertical stringing even more than mv.

At 50 yards, I'd say the barrel movement absolutely drowns out mv variation. Couple years back when I first started playing with a tuner, I set it up once in a way that produced over an inch of vertical at 50 yards. Same rifle that I later went on to shoot 1/4" with. Would be interesting to repeat the chrono test with a tuned rifle to see if mv correlates with POI as would be naturally expected following the laws of physics. As for the naked barrel, I think it sufficient to say that results are unpredictable.

 

[Mystic Precision]

To answer the title.....Yes

There is no reliable correlation between MV and impact on target...rimfire or centerfire

Glad you now have some firsthand experience...

Jerry

 

[grauhanen]

To answer the title.....Yes

There is no reliable correlation between MV and impact on target...rimfire or centerfire

Glad you now have some firsthand experience...

Jerry

Jerry, I used chronographs quite a bit in the past when tuning PCP rifles, so I wasn't surprised by what I saw. It confirmed what I saw years ago, only this time with .22LR.

As for the assertion that "there's no reliable correlation between MV and impact on target" -- it goes too far. It suggests that MV doesn't matter, that it doesn't affect dispersion. This isn't supported by the majority of data published on the topic. MV and ammo behaviour often have an obvious relationship. Although I don't know directly from personal experience because I don't shoot centerfire, I suspect that MV consistency is one of the most desirable characteristics of CF ammo for the very reason that it helps reduce dispersion.

For rimfire ammo in general, there is often, perhaps usually, a relationship between MV and POI. That is to say, POI and MV are often but not invariably related. There are other factors at play to help explain what is seen in .22LR ammo performance.

This view is confirmed by Larry Landercasper (Landy), who posts as HuskerP7M8 on various forums, including Rimfireaccuracy.com. He is a widely respected rimfire ballistician who has a very good reputation for understanding .22LR behaviour. He summarized the issue for readers this way:

As already pointed out by Jerry [Stiller] and myself, velocity variation is not the only source of dispersion we're forced to deal with. If we somehow miraculously found a magical lot of ammo where every shot had the identical velocity, we'd still shoot relatively large groups relative to short range centerfire BR.
There will never be a perfect tune or perfect ammo that results in every bullet going thru the same hole in rimfire.
Malleable unjacketed lead projectiles simply can't be manufactured to the same tolerances as their brethren in the centerfire world and even if there was some major breakthrough that allowed the possibility of perfectly formed rimfire bullets....they'd still be modified to less than perfect due to the difficulty of achieving uniform obturation of the bullet's heel, consistent alignment with the bore to minimize in-bore cant, and then hoping the bore dimensions don't further change the bullet's shape.
See post #52 http://www.rimfireaccuracy.com/Forums/showthread.php/9337-Velocity-variation-and-chamber-barrel-prep/page3os

Ballistics calculators show the potential, often likely, behaviour of .22LR ammo. They are useful in explaining why a lot of what happens on target occurs as it does. A higher POI, for example, is often the result of higher MV. Not always, but often. The results of ballistics calculations should be of great importance to those who shoot at longer distances. They don't explain all results, but they are a good start. The claim that there is no reliable correlation between MV and impact on target is overreach and as such is a disservice to shooters.

It's well worth the time to point out that MV doesn't always explain results. It certainly doesn't illuminate why horizontal dispersion occurs. The thing is with rimfire, when there are some helpful ways to understand ammo behaviour, they shouldn't be completely thrown out the window because they don't explain it all the time.

In physics it appears impossible to have theories that without controversy explain everything by unifying relativity and quantum mechanics. On a much more relatable level, it's difficult to find an explanation that makes all rimfire behaviour completely understandable.

 

[Mystic Precision]

Often, sometimes... when I dont drink too much coffee. Common rebuttals when someone really wants a theory that isn't working to work.

A theory is there to try and explain an observable event in the real world. That theory should explain and thus predict the event at a very very high rate of confidence... like 99% type confidence (when you get to 100% confidence, they call that a law). Otherwise, it is merely an opinion or conjecture.

Like the Black swan, you don't need a large sample size of contradictions to discount a theory.... and you have confirmed what I have observed many years ago, MV isn't a reliable partner in predicting what will happen on target at distance... whether rimfire OR centerfire.

If MV did matter, then all shots from every rifle in every chambering under all circumstances WOULD agree with the theory... it doesn't and you don't need to work hard to find these many exceptions. In fact, I would love to see someone demonstrate with more then a few shots that they have a combo where EVERY shot has the higher MVs landing higher on the target, the lower MVs landing lower on the target. Then duplicate it with a second rifle... or more if they are really ambitious.

I never could....oh yes, I did play with MV/ES/SD many years ago in hopes it would improve my LR results.

Because this is an unreliable partner, I don't worry about it. I put no weight on MV stats when trying to find the best combo for any rifle.... I let the target at distance tell me all that I need to know.

For me to understand and improve, I get rid of all the data, beliefs and vudoo that are unreliable or non repeatable. It seems to be working.

YMMV

Jerry

 

[Maple57]

Part of the problem with chronographs is they have an accuracy level that in most cases is greater than the goal we are attempting to achieve. In manufacturing we inspect with an instrument that is known to be at least ten times more accurate than the accuracy level we are attempting to measure. Few chronograph systems can meet that standard and none of them are remotely affordable.

At this point I'm not sure if the chronograph is testing the ammo or if the ammo is testing the chronograph. At best it provides a rough idea of the velocity... rough. We can take our chronograph numbers and add a grey area around every value that is equal to the accuracy window. Value says 1030 may be as low as 1010 or as high as 1050 perhaps. (depending on model.)

As for fast rounds hitting high or low, from a strictly ballistic perspective, yes absolutely fast rounds will hit higher. That is a mechanical fact.

From a mechanical perspective, barrel harmonics do come into play and a faster round may or may not result in a higher launch attitude at a certain temperature. Sometimes barrel oscillation is not from 6 to 12, in my experience it is usually from 8 to 2 o'clock but mileage does vary.

That being said, as the distance is increased or decreased one or the other will become the prevailing influence.

At short range, POI is influenced more by barrel harmonics than drop factors.

At long range, drop factors will more than overcome differences in barrel oscillation.

Even small bullet diameter and hardness variations will affect barrel harmonics and muzzle velocity if you consider the variable swaging pressures required.

 

[Mystic Precision]

And why I let the target tell me all I need to know.

It is simply way too complicated to try and model LR results with a very flawed metric... and it doesn't even begin to touch on other more relevant issues surrounding external ballistics.

Jerry

 

[grauhanen]

None of what I've posted in this thread should be taken as conclusive evidence of anything. After all, only one target is shown, the ammo is admittedly inconsistent, and the chronograph data is very small in size.

Having said that, however, there is an observation that is worth making. Below is the target with the vertical dispersion shown for each five shot group. Also shown is the extreme spread (ES) of the five rounds in each group.



It's noteworthy that each group that had less than .250" of vertical dispersion had a relatively small ES for the five rounds. The three groups with the least vertical, had spreads of 17 fps or less. Of course, a smallish ES didn't guarantee a group with a smaller amount of vertical.

While not conclusive given the very small sample size, this suggests that to achieve low levels of vertical dispersion, a low extreme spread is an important component of the ammo. More testing with a chronograph may confirm this.

 

[grauhanen]

My previous post became somewhat lengthy, so I thought that it would be better to add this in a separate post.

A low ES and small vertical spread is not to say that consistent MV -- that is, a small extreme spread -- is the most important characteristic of ammo. There are too many other factors at play in rimfire accuracy to put all the eggs in a single basket.

All barrels are different and over time each one can change (although the change is usually very gradual). They can be different in the most obvious way of length, but they also differ in ways such as metallurgical composition, bore diameter and bore diameter consistency, characteristics, condition, and consistency of rifling, as well as chamber characteristics. Because of such differences, the same lot of ammo is very unlikely to perform the same way in two different barrels.

To further muddy the waters, all ammo within the same lot may not perform the same even in the same rifle. The ammo may, tend to perform similarly but there is room for variation between different boxes of ammo within the same lot.

Few of us have had the pleasure of shooting "killer ammo" -- ammo that shoots consistently from one box to the next and which often shoots well across a number of different rifles. Most of us get ammo that produces some very good results but doesn't always do so.

While we wait to be blessed with killer ammo, we can look for ammo that has two characteristics. One, ammo with ass low an ES and SD (standard deviation) as possible, and two, ammo that shoots well. It's unlikely that good shooting ammo will have a wide ES and high SD, even if a low ES isn't always in itself a guarantee of good results.

 

[Mystic Precision]

the bottom 5 targets confirms what I have been saying.... Velocity and velocity related data is not a good indicator of what will happen on target.

ES 14fps had the smallest and one of the largest verticals - why weren't the 2 groups the same? I mean there is almost a 3 fold difference in result...and the groups look to have been shot sequentially.

ES 15 and 13fps both have taller vertical then 22 fps. And taller then 14fps. What gives?

Add the top 5 groups... ES16fps had the smallest vertical of them all.. 17fps was pretty darn good. So maybe we need a certain ES???? But then there is that pesky 14fps group...

There is a sample size of 10 groups (50rds) which is a very nice size sample... All shot on 1 target, environment is likely very similar, same shooter, same rifle, blah, blah, blah..... and there is no pattern that can be concluded from any of these targets.

Essentially a pointless metric for anything... but there is a tendency to pick and choose data points to try and make a narrative work.

If ES/SD mean anything, it works this time, next time, all the time.... it didn't and your groups show again how ES/SD is an unreliable partner in trying to predict results on target. Add some distance and see how things play out.

If there are those who can show groups where ES actually plays out as the theory suggests, love to see the groups.

And that can be centerfire as well.... I will give a hint that you should consider looking at the 6PPC and 6BR to have the best chances of proving the point....

223, 308, 30-06.. that is going to be a lot harder.

magnums? that could be more work then it is worth.

enjoy.... I look forward to being proven wrong....

Jerry

 

[Biologist]

Hi Grauhanen. I think its awesome that you posted results from this experiment. I know how much work and effort it takes to do so.

I don't mean to be critical, but I don't think this experiment's results allow conclusive answers. Several reasons have already been discussed. In addition, the atmospherics will account for alot of variation. Unless the test is done as per the methods that the Eley and Lapua test labs use (inside, zero wind or air movement, stock removed and barreled action clamped into a vice designed for that action, super-high precision measuring equipment, etc), then there are too many other variables going on that will confound the results and lower confidence in discerning a data trend.

In other words, I think you confirmed, as you stated, that indeed there is way more going on than just muzzle velocity.

But its still fun to experiment, we all do. And most of us will never have the opportunity to shoot inside a testing lab, so we carry on. So I plotted your data from your image in post #11 image, with Vertical on the Y axis (as a surrogate for elevation), and ES on the X axis. It is a scatter plot with no emergent trend. The Excel fitted regression line R squared value is 0.0017, or 0.17%, meaning that the ES has nil influence on the elevation per group. This is of course expected because ES is a stat, not the true independent variable. MV is the true independent variable if you are measuring response of POI and analyzing for vertical elevation. Therein lies the clue for setting up your next experiment!

Measuring the ES of the group's MV is not the stat for getting at the questions of MV relationship with POI. In fact 5-shot groups expressed as an average ES nullify the statistical validity of MV and POI interpretation. Instead, if one is measuring elevation of the POI (the response), then the sample to measure is the individual shot's MV. The data table to provide for stats analysis is the Chrono speed per each shot, and that individual shot's POI elevation. Shoot single shots per aiming point on paper and record MV and elevation per shot. Its going to require alot of paper, (I suggest at least 30 shots with individual vertical measurements) but its a fun experiment to do.

I have not done such a test with .22LR rimfire. But in centerfire doing ladder tests from min to max load, one of my rifles is consistent with a non-intuitive trend when I test at 200 yards: From min charge and increasing (e.g. in 0.5gr charge increments, same brass, primer, bullet, seating depth), the POI elevation consistently rises until about half way to max charge, and then the POI elevation will either level off with no change, or will decrease POI approaching max charge and at max MV. I have not analyzed this precisely, but the drop at high and maximum charge and highest MV is often about 1/2" to about an inch lower than slower charges. It shoots lower with fastest MV at 200 yards! Again it just goes to show there is alot of unknown stuff happening with barrel harmonics.

Assuming your chrono is accurate enough, with a zero wind day, and high precision shooting, with a sample size of single shots large enough, you might be able to tease out a trend of MV versus vertical POI. One potential confounding issue in my rimfires however, is change in POI elevation as the barrel fouls. Starting with a clean barrel, and about 10 to 20 rounds to foul it, POI will eventually shift after about 50 rounds or so. Its unpredictable when and how much, it might be closer to 100 rounds fired, but I see it all the time when practicing. My hypothesis is that the barrel's internal chemistry and physical structure is changing, or in other words, gunk (burnt powder, carbon, lead, lube, etc) is accumulating and changing internal stuff. Maybe this internal barrel change in gunk and POI shift could be controlled for with MV measurement. Hypothesis: As the barrel fouls, POI shift will be reflected in MV.

Rimfire is terribly frustrating!

 

[emerson]

Rimfire is in fact terribly frustrating.

 

[grauhanen]

the bottom 5 targets confirms what I have been saying.... Velocity and velocity related data is not a good indicator of what will happen on target.

ES 14fps had the smallest and one of the largest verticals - why weren't the 2 groups the same? I mean there is almost a 3 fold difference in result...and the groups look to have been shot sequentially.

ES 15 and 13fps both have taller vertical then 22 fps. And taller then 14fps. What gives?

Add the top 5 groups... ES16fps had the smallest vertical of them all.. 17fps was pretty darn good. So maybe we need a certain ES???? But then there is that pesky 14fps group...

There is a sample size of 10 groups (50rds) which is a very nice size sample... All shot on 1 target, environment is likely very similar, same shooter, same rifle, blah, blah, blah..... and there is no pattern that can be concluded from any of these targets.

Essentially a pointless metric for anything... but there is a tendency to pick and choose data points to try and make a narrative work.

If ES/SD mean anything, it works this time, next time, all the time.... it didn't and your groups show again how ES/SD is an unreliable partner in trying to predict results on target. Add some distance and see how things play out.

enjoy.... I look forward to being proven wrong....

Jerry

Jerry, one of the amazing things about .22LR shooting and in particular the ammo that we use is that there is a peculiar quality about it that's hard to systematically quantify. The behaviour of this ammo can often defy expectations and explanation. It can be unpredictable. That's what this lot of ammo is like, at least in the two rifles I've used it with most recently. It was at times erratic and the results unforeseeable.

That's what I meant when I noted that this CX ammo was inconsistent. Sometimes it produces very good groups, at others it gives results that are quite baffling. That's the nature of .22LR, at least those lots that aren't killer lots capable of consistent behaviour almost all the time. It must be acknowledged that part of the problem lies in imperfect barrels. No .22LR barrel is perfect, and an Anschutz barrel certainly isn't at the top among the contenders that come closest.

The result of both these factors is that ammo performance isn't always as expected. You are right to point to the groups with wide vertical dispersion and low ES. They are the ones that don't go as anticipated. The reasons have to do with the ammo most of all. It isn't consistent, as I noted in the first post. This means that it doesn't do what it should. What is more significant, however, is that none of the groups with the smallest vertical dispersion had wide extreme spreads. While not proving anything conclusive, it suggests that ES is related to the low vertical spread groups had -- despite your casual dismissal of any relationship between MV and POI. You can't ignore that, while focussing on the data that supports your view that MV and POI have no relationship whatsoever.

The point I've been trying to make is that sometimes MV and POI don't match. The groups with the smallest vertical spread indicate that sometimes they do. Of course further testing would be needed to be more conclusive.

If, as you say, MVs are a "pointless metric" then you have to accept that ammo behaviour is completely arbitrary, that it doesn't matter whether the ES a particular ammo is small or considerable because it ostensibly has no relationship to how the ammo performs. You're right that it in itself doesn't guarantee good results. But it can and often does matter. While MV variation isn't the only cause of dispersion, it is one of them.

As for adding some distance, results in a non-test tunnel environment make such data increasingly less and less reliable. When shooting outdoors the movement of air anywhere along the path between the shooter and the target make it more and more difficult to know how uncontrollable influences affect results. Furthermore, erratic ammo behaviour is only worse at increasing distances. In other words, it can sometimes be hard to tell what's influenced your results at long distances -- air movement, ammo inconsistency, or shooter error, all of which are compounded.

 

[grauhanen]

Hi Grauhanen. I think its awesome that you posted results from this experiment. I know how much work and effort it takes to do so.

I don't mean to be critical, but I don't think this experiment's results allow conclusive answers. ...

In other words, I think you confirmed, as you stated, that indeed there is way more going on than just muzzle velocity.

You've rightly noted that I suggest that there is more happening than simply the results of MV. But I've tried to be careful not to suggest anything conclusive about what I've shown. In the first post I said

I understand that one target and one set of chronograph data is a limited amount of data. I thought it was curious, however, that the conventional wisdom that rounds with a higher MV will strike the target at a higher POI than those with a significantly slower MV. It suggests, but clearly not prove, that there's more to ammo behaviour than MV.

In post #11 above I was more explicit.

None of what I've posted in this thread should be taken as conclusive evidence of anything. After all, only one target is shown, the ammo is admittedly inconsistent, and the chronograph data is very small in size.

The small size of results I've shown suggest some things, but clearly they don't prove anything.

You're quite right, of course, that rimfire can be terribly frustrating. Ammo behaviour with typical lots can be quite unpredictable even when most everything else -- including the calmest conditions, a decent rifle, a solid rest and bench, good shooting technique, and keeping the tongue in the middle of the mouth -- is taken into account. Sometimes a certain ammo can give very satisfying results, sometimes it produces exasperation.

 

[Mystic Precision]

Assume you dont reload centerfire? As someone who has experimented, tested and competed for 20 yrs, you get a chance to play around with each component and with the volume of shots fired, you get a sense of what does what.

When you can control EVERY part of the kaboom, you can play around and test its affect on target. With rimfire you have zero control in what you shoot and worst, no way to test BEFORE you shoot. There are many many assumptions in what is in each box of ammo... and often no way to confirm it cause the evidence is gone.

I will say that rimfire for me over the last many years has proven as frustrating and as elusive as it has with you... and I know you have tested and tried far more then me in this area. My solution is to play a game where the faults and flaws are still within the targets I need to engage. I accept its limitations and create systems that maximise the performance.

Think of each component in a piece of ammo and know that each, has variations. And all those possibilities and combinations can vary to a larger or lesser degree in each rd of ammo. The factories have figured out that despite their best efforts to create uniform and repeatable ammo, they can't.. in fact, they really have no way to even come close.

Their only choice is to make a crap ton of it.. sort as best they can.. test and then put the 'best' stuff in the expensive boxes that go to National and Olympic shooters. The rest they sell in falling grades to various levels of shooters.

By the time we get to Lapua CenterX, how far away are we from the 'best' they can make? as a measure of % of flyers or dispersion from the center, how bad is it? And this is what we consider good stuff... or good enough.

So, if you are going by a metric that, as I have said, is plenty flawed all on its own... trying to use it to help explain or predict some pretty flawed ammo, that is just a world of frustration. Just know that I work in a world where every component is measured and held to the tightest tolerances we can AND there is are still variations that don't support the theory of MV meaning much.... I think using it to predict some pretty flawed ammo is not going to end well.

Put MV aside for a moment... think about the priming mixture, powder weight/type/burn characteristics, case, annealing, length, crimp... and then add in all the variations that can happen from a swaged lead bullet, lube and fouling... you got a lot of fish to fry. Which one(s) is varying in the next cartridge?

Why I just let the target work out all the math, science and witchcraft.... if it holds to the level of consistent accuracy I need to play my game, I use it. However, if a box shows enough variations, that gets put aside. I don't need to figure out why... I just need to know it isn't good enough and move on... besides there is nothing I can do to change it.

There are many things that can affect the POI of a bullet..... I think a really fun experiment you may want to look at is strapping on a pressure gauge to your barrel and plotting that data. All sorts of goodness learning about pressure curves, dwell time, harmonics and nodes... and how fouling can affect all of this.

Or consider centerfire reloading where you can test the affects of each components... I accept what rimfire is and what it isn't.... and I just shoot at larger targets.

Jerry

 

[Mystic Precision]

Here is how sensitive our systems can be to cause group size changes (thus POI changes). I am testing my 308 win FTR rifle using some of the most precisely made bullets, controlling every aspect of the ammo... literally.

The group on the right is a good load for FTR at the level I competed at. The drift to the left is due to the mirage slightly picking up (optical push to the left). I didn't change my POA. At 250yds, this is the level of vertical that is possible in modern F class rifles.... essentially no vertical dispersion.

The group on the left has a meager increase in powder charge of 0.2gr... that would be 8 kernels of Varget in a load that is over 42grs of powder. Do the math on how small that percentage change is... and how much it can affect a very large system. Note the change in the group center vs the group on the right.

Now consider rimfire ... if you can access a lab grade milligram scale, weigh the powder charges. It would not surprise me there is a variation around 0.1gr... but the powder charge is around 1gr. This one single component variation is likely the cause of most of the variations you see...

And it isn't going to change your velocity numbers all that much... if any. I don't bother testing my ammo but it wouldn't surprise me if my group on the left had tighter velocity numbers vs the group on the right.

Jerry

 

[Maple57]

I have so frequently fired low round count groups that vary significantly in size with the exact same load, only minutes apart.

With nothing changed, trying to attribute cause from small round count sizes are like reading tea leaves.

It's a place to start, sure, we have to start somewhere, but we need to be careful not to attribute results to what we think we want to test without considering all the other things that contribute.

I did have a rifle that consistently shot extremely well once upon a time, but once it was over it was never to be found again. 1/8" groups at 100 yards were normal. Velocity spreads were 1 FPS ES most of the time. (According to my Chrony) The barrel lasted for 800 rounds and that was the end of the rainbow. The new barrel never shot like that, it was more... normal.

The point is that when you have such a rifle, testing is efficient. Most rifles can never shoot like that and there is random built in all over the place. Once you start testing inside that natural random, the results are hard to pin down. This is much like the old days where TR shooters used issued ammo for DCRA. All they could do was try to center up the group and it was a big group.

We just have to try and work it out in the aggregate and see what works best over time.

As for Gerrys post regarding a lab grade milligram scale, I do have one. (Vibra HT) The problem with a 22LR is the small powder charge is so small that even with the accuracy of a milligram scale, the percentage of error would be meaningful.

Having such a scale is very nice... I can weigh the ink used to sign your name on a piece of paper.