What benefit is the Chronograph?

[qajaq59]

This may seem an odd question, but I'm serious.
There are a lot of reloaders using chronographs so there has to be a benefit to using them. I've always loaded for accuracy on the target and never really paid much attention to the velocity. However, I may be missing something. Why are you using them and how will getting one improve my shooting accuracy.
Thanks for any info.... Qajaq59

[Castaway]

I have one and like using it.  Most of what I do is to check final velocity after I find an accurate load.  I've also used it to determine extreme spread and Standard Deviation to verify a potentially accurae load.  The best use I've found though was on the CMP site ( http://www.odcmp.com/ ) where they give guidance for reloading for a Garand.  Specifying IMR 4895 powder (and another which I don't remember) they tell you the operating velocity range to properly function your rifle.

[Grumulkin]

I got a chronograph for Christmas and haven't yet used it.  I also load for accuracy and not velocity.  I will use the chronograph though so I can know how fast my loads are compared to others.  Also, if you want to use ballistic tables, you need to know how fast you started your bullets; I think that's what will be most useful for me.

[Questor]

I use it to verify that my loads are performing as the load designers expected they would. There are really two components to this kind of confirmation:
1) A loading manual that gives velocities that are close to what one can reasonably expect from a typical firearm (as opposed to velocities from a test barrel.) Speer does the best job at this.
2) A chronograph.

If the load book says I should be getting 1300fps and my chronograph says I'm getting 1600fps or 1000fps, then something's wrong.

In summary, I use it to help me develop optimal but safe loads.

It doesn't do anything for my accuracy except to help me calculate trajectory and wind deflection for long shots.  Velocity is a key component to this calculation.

[james]

My daughter did a science project with the powder being the only variable and loaded three rounds in .5 grain increments from the min. to max +.5.    Not suprisingly the most accurate loads had the smallest spread in velocity.  The most accurate was the max which had a 8 fps range.  The least accurate was one grain over minimum which had a 345 fps spread.
For hunting, I want a fast load, but for targets I just want accuracy.  The chrono helps me get that.
james

[beemanbeme]

A chrony gives you data! Factual data.  Not generic info from the back of a load book.  With that data, you can compute your trajectory to a certainty.  Additionally it can help you determine the operating maximum for YOUR rifle.  As you increase the powder charge, your velocity should follow a somewhat straight increase.  When that gain stops or flattens out, you have reached the operating max for your rifle.  More powder (even if within book limits) will only cost you barrel life.  Also, say the book sez a certain 30-06 load of xxgrs of xx powder give you 2800fps and 50,000# pressure.  If I reach 2800fps, even if I'm below the max book charge, I make the assumption that I'm at 50,000# pressure and call it done.  I may have a tight chamber or a fast barrel but the pressure is there.  
Actually, a chrony can give you so much info, that how fast your bullet is going is kinda a minor part of it.   :grin:

[EsoxLucius]

As you increase the powder charge, your velocity should follow a somewhat straight increase. When that gain stops or flattens out, you have reached the operating max for your rifle.

This is an important aspect of using a chronograph.  However, one should look for any change in the rate of increase in velocity with incremental increases in powder charge.  This could be a slower increase in velocity, no increase, or a faster increase.  In addition, this only gives one an indication that one may be nearing a maximum load.  This information must be used with other indicators as it alone cannot tell one when they have reached the operating max for a given rifle.

A chronograph also allows adhering to "do not exceed the charge or velocity of a maximum load".

[leverfan]

I agree with the reasons that folks have been listing, and I have one more.  If you compete in a shooting sport that has minimum or maximum velocities, you darn sure better know what velocity your ammo is producing before you go to the big match.

[ricciardelli]

A chrony is an instrument and a tool.

You could ask the same question about the speedometer, tachometer, oil pressure, water temperature and ammeter in your car.

Or, the dial on your radio or the channel indicater on your TV.

You can do just about anything you want with three adjustable wrenches, so why have a full set of 1/4", 3/8" and 1/2" metric and American socket sets?

Loading for accuracy is what it is all about. However, I was working up loads for a particular .22-250 a couple of years ago.  I was really inpressed with the grouping ability of a particular load.  When I ran it through the chronies I was informed that the 52 grain bullet was doing all of 2100 FPS!  Duh?

Great for punching paper at 100 yards or less, but definately not up to the capability or the intended use of a .22-250!

I loaded for around 25 years before I bought my first chrony...for the past 20 years I don't leave home without it...

[Danny Boy]

I loaded for around 25 years before I bought my first chrony...for the past 20 years I don't leave home without it...

A few weeks ago I took my Shooting Chrony Beta to the Canadian dealer for re-caliberation. There was nothing wrong with it but I just wanted a check-up. The unit was adjusted and now shows my bullets flying 150+ fps faster than before.

For my 300WM load with 72.6 gr of H4831 it now shows 3060 fps instead of 2900 fps. Well I have to tone down my loads for this summer.

I was told the two sensors get loose over time and need to be recaliberated once in a while. Did you get a check-up on your chrony?

Danny

[ricciardelli]

I have three Chrony units.

Two F-1 units.  One is the original model and the second one is a later model.

My third unit is the Gamma Master.

If I place all three "head-to-tail" they don't measure more than 5 FPS difference with a 2992 FPS load.  So I guess I don't have to have them calibrated.

[beemanbeme]

uhhh, your increases in velocity are not going to follow a straight line as you increase your powder charge!  Its called diminishing returns.  There will be a slightly less gain for each increase.  If you plot the gains, you will find they follow an arc, not a straight line.  When you reach a point of insignificant gain or no gain, then you have reached an OPERATING max for that rifle with that powder and that bullet.  

[Questor]

...Correct. An more important, your pressure won't increase linearly either. A half grain of powder when nearing the maximum charge in a nearly full case can make a very significant difference.

[Coyote Hunter]

What benefit is a chronograph?  Whether you load for accuracy of velocity – or both – a chronograph can help you get what you want out of your loads.


Before I got my chronograph I had one way to develop rifle loads – build between 3 and 5 cartridges at each of several powder charges using 0.5g increments, take them to the range and shoot each powder charge at a different target.  I generally shot between 30 and 40 rounds to determine what the best load was.  Now I do things a bit differently and often come up with a winning load recipe with less than 10 rounds fired.

Accuracy is, to me and with rare exceptions, the Holy Grail of load development.  Accurate loads, by definition, are consistent performers.  They may not have the highest velocity and often don’t.  They may not have the lowest Standard Deviation or Extreme Spreads, either, but they often do.  A chrono helps measure consistency in ways that a paper target cannot.

A chrono will tell you exactly what the velocity increase is with each increase in powder charge.  It can help you determine which powder is the least sensitive to variations and which is the most sensitive.  Don’t like to hand-weigh charges?  This becomes very useful information.

Not sure what the velocity/powder charge curve looks like?  A chrono will tell you.  I generally try to find loads that are still in the more or less linear part of the curve.

Wondering if a particular load is safe in your rifle?  A chrono will provide valuable clues.  As a general rule, you should not exceed either the powder charges OR THE VELOCITY of published data.

Developing a hunting load and wondering what the trajectory is?  A chrono provides an important piece of the puzzle.  (The bullet’s Ballistic Coefficient and a ballistic calculator, like the free “Point Blank” program from www.huntingnut.com, provide the rest.)

Sometimes I still revert back to my old ways when developing loads but these days I will usually load one cartridge at each powder charge.  At the range I record the point of impact and velocity for each cartridge.  When finished shooting I compare the velocities and targets.  Sometimes I decide a particular powder isn’t going to do what I want, other times I find a reduced range of powder charges I want to test with more loaded cartridges at each powder charge.  Quite often, however, I can look at the results and pick out a very good load even though I’ve only fired a few cartridges, all with different powder charges.  The velocity information provided by the chrono really helps.

These days I don’t do ANY load development without the chrono.  That includes loads like my .308 Win equivalent loads for the .300 Win Mag, where pressure was so low as to not be a concern, or full-house loads where pressure is a major concern.

Given the low cost of chronographs (rebuilt Shooting Chronys can be had from the factory for $50), its my opinion that anyone who is working up to max loads and doesn’t have one is more than a little foolish.

[Coyote Hunter]

Double post -- deleted

[PaulS]

The only thing I use a chronograph for is to provide me with accurate information on the velocity of my ammunition.
A chronograph cannot measure or predict pressure. (actual or relative)
A chronograph will not tell you which ammunition is going to be the most accurate.

After I work up a couple of accurate loads - by printing good groups on real targets over a period of weeks the chronograph can do this for me:

It can tell me what the average velocity is - I use that to predict the average ballistic trajectory for that ammo in my gun. I can predict changes due to elevation, humidity and temperature. I use a computer and ballistics software for that.

The chronograph can tell me how much velocity is between the fastest and slowest of my ammunition. I can use that to find out how far off the ammunition is possible to shoot from its average trajectory.

The chronograph can tell me the mean average deviation and the standard deviation within the sample that I shoot. That tells me the chances of actually hitting the average trajectory that results from the average velocity.

The chronograph is a tool that can be used by the hunter to understand his ammunition and where it will shoot most often under any set of conditions that you can plug into your computer software. Without the chronograph you have no way of knowing the velocity of the bullet coming out the muzzle of any of your guns - whether you reload or shoot factory ammo.
It is an invaluable tool that cannot be replaced by anything else - short of shooting in every location, under every condition that you are going to shoot and recording the data and variables associated with that location.

[Don Fischer]

I use mine the same as Paul. Mine does have a built in ballistics calculator tho. Gives me trajectory out to 500yds at 50 yd increments. Might give longer ranges and shorter increments, never tried it. Pact Mk 4.

[Coyote Hunter]

PaulS –

I basically agree with your comments, but for the benefit of reloaders without chronographs, or with little experience with them, I would like to make some additional observations.  They are, of course just my viewpoint.

The only thing I use a chronograph for is to provide me with accurate information on the velocity of my ammunition.

That’s basically all they do.  Some have statistical functions built in, something I use a spreadsheet for, but that’s just another way to look at and analyze accumulated velocity data.

A chronograph cannot measure or predict pressure. (actual or relative)

I would agree with “measure or predict” when it comes to “actual” pressure, but in terms of relative pressure I would disagree.  There is a well established correlation between pressure and velocity.  Granted, you cannot take loads using different components and assume that the higher velocity load has higher pressure, but when working up to a published and pressure-tested recipe a chronograph can provide valuable clues as to what the relative pressure might be.  

One reason I prefer Hodgdon and Accurate data is they provide actual pressures for their starting and maximum loads.  When I use their data for load development I compare my starting velocity to theirs.  This provides a reference point.  While I would hesitate to call it a ‘calibration’ point, it does provide an indicator of what I can expect as I increase powder charges.  For example, if my starting velocity is significantly higher or lower than the book value, I can reasonably expect that velocities at maximum powder charges will be off in the same direction – and I will adjust my load development plans accordingly.  On the other hand, if my starting and maximum velocities and powder charges are reasonably close to the book value, I can generally and reasonably expect that my pressures are safe.

Obviously the best method for determining pressure is to have loads checked in a well-calibrated pressure barrel, but few of us ever have that done.  And, unfortunately, signs of excess pressure may not exhibit themselves until well after dangerous levels have been reached.  This is particularly true, for example, in lever guns but also holds true for bolt rifles chambered for high-pressure cartridges.  In lieu of pressure signs, the reloader has two ways to try and assure safe pressure levels.  One is by following published recipes exactly and by not not exceeding published powder charges.  The second is by following published recipes exactly and by not exceeding published velocities.  Neither method provides a guarantee

Some time ago I read an article that claimed an extra 100fps from a near maximum load could take 10,000CUP of additional pressure.  (Or maybe it was PSI, I don’t remember.)  The point is that the relationship between velocity and pressure exists and plotting the powder charge vs velocity curve can ***help*** a reloader stay out of trouble.

A chronograph will not tell you which ammunition is going to be the most accurate.

I agree, but have often found that my most consistently accurate loads are also the most consistently consistent in terms of velocity.  I have a couple loads where shot-to-shot velocity varies considerably more than I would like, yet the loads provide very good accuracy.  Such loads, however, are in the minority.  

There is also the problem of shooting “into” or “out of” a group when doing load development.  Was a great 3 or 4 shot group a statistical aberration, nothing more than luck?  Was a bad group due to shooter error?  When making a final determination as to a load I will use, I look at the target groups for each powder charge as well as the velocity data for each powder charge.  Further, I will compare the results for individual powder charges with those for their immediate neighbors.  Ideally I will find a range of powder charges that provide both accuracy and consistent velocities and I will pick a particular load from within that range to be my final load.

The chronograph is just another tool and it measures velocity. Its not a crystal ball, but the data it provides can help the reloader develop consistent and accurate ammo and do so with fewer shots fired.

[EsoxLucius]

uhhh, your increases in velocity are not going to follow a straight line as you increase your powder charge! Its called diminishing returns. There will be a slightly less gain for each increase. If you plot the gains, you will find they follow an arc, not a straight line. When you reach a point of insignificant gain or no gain, then you have reached an OPERATING max for that rifle with that powder and that bullet.

So, is this an absolute? There is always less gain for each increase?  There is never a straight line, even partial, in a plot of incremental powder charge and velocity.  There will never be an instance when velocity will spike in a significant increase over previous increments?  When a point of insignificant gain or no gain is seen then one has always reached an OPERATING max for that rifle with that powder and that bullet?  Thank you for your consideration.

And a question for PaulS:  So you are saying there is no correlation between velocity and pressure?

[beemanbeme]

velocity and pressure must correlate as the big ammo companies (win/rem/fed/etc) buy their powder by the ton(s) and then the guys with the white coats play around with it until they figure out how much is needed in xx case to produce xx pressure.  From that they quote velocity figures.

I had a 22-250VS that I used for Pdog shooting.  I had worked up a good load, etc,etc.  Each spring, before I started Pdog shooting, I would reset my COL to where the bullet was just touching the lands.  Because of throat erosion, the cartridge would be longer than the previous year.  I would then make small adjustments in the powder until it was shooting at the same velocity of the original load.  It would shoot to the same point as the year before.  When I finally sent the rifle off to be rebarrelled, I was loading above the book, but, considering the greater length and such, I feel it was entirely safe as I never exceeded the original velocity that was well within the book.

[Bullseye]

Have really been thinking about buying one lately, but cannot convince myself I need it or would use it after checking my loads.

Sorry guys, but after reading all the posts I am still sure it would do anything useful for me.

I have developed accurate loads for all my guns without it, guess I do not need it now.

[Don Fischer]

Bullseye, the best thing about my cronograph is that by knowing the actual average velocity it will then calculate the trajectory path for me and let me know exactly where to sight in my rifle's for max point blank range. Even with the avaliable table's on trajectory, it's all just speculation if you don't know your actual velocity. For instence, if you sight in for a max point blank range at a 6" target, my cronoghaph will tell me just where the bullet is at 50 yd increments out to 500yds, and at what range the bullet is 3" high and 3" low. It also show's the fall off beyond the max point blank range, mine is suprizingly accurate in shooting test's.

It's also a hoot to take out someone who is using factory ammunition and let them see what their stuff is doing as apposed to what the factory claim's are!

[EsoxLucius]

beemanbeme and Questor:

uhhh, your increases in velocity are not going to follow a straight line as you increase your powder charge! Its called diminishing returns. There will be a slightly less gain for each increase. If you plot the gains, you will find they follow an arc, not a straight line. When you reach a point of insignificant gain or no gain, then you have reached an OPERATING max for that rifle with that powder and that bullet.

...Correct. An more important, your pressure won't increase linearly either. A half grain of powder when nearing the maximum charge in a nearly full case can make a very significant difference.

So, is this an absolute? There is always less gain for each increase? There is never a straight line, even partial, in a plot of incremental powder charge and velocity. There will never be an instance when velocity will spike in a significant increase over previous increments? When a point of insignificant gain or no gain is seen then one has always reached an OPERATING max for that rifle with that powder and that bullet? Thank you for your consideration.

[PaulS]

Coyote Hunter,

Velocity and pressure do not go hand in hand. My brother and I have two guns that are as close to twins as they could be - serial numbers are less than 10 apart - and there is more than 10% difference in velocity between them with the same load - same pressure. If he added powder to make up for the 180 fps he is slow compared to mine he would be replacing parts before he got to the velocity that I get. The guns are 6" revolvers and I get 1464fps in mine and his gets about 1280fps. The loads are close to maximum but about .7 grains from published maximum. I get almost the published velocity (from the Speer manual) in my gun - accurate loads!
You can't use a chronograph to determine pressure -relative or otherwise. A tight barrel will slow a bullet down and a loose barrel will speed it up. The amount of freebore or the length of the lead just beyond the thoat has more influence on velocity than pressure and if you have minimum of all of them and a tight barel you are never going to see published velocities without seriously overloading to get it.


EsoxLucius,

What I am saying is that there are factors that affect velocity a lot more than they affect pressure. I know the physics of pressure times area equals force. But you have to add to that the friction in the barrel (no two guns are alike), the chamber size, length and angle of lead, amount of freebore, and even the individual harmonics of the gun. I am saying that I have proven for myself that velocity can vary more than 10% with the same components in two nearly identical guns with only six inches of barrel. There is a lot more room for differences in 20 or 24 inch barrels.


beemanbeme,

Those guys in the white coats don't give a little white slipper about velocity - they load to a level where they are below maximum pressures and they get a reasonable amout of velocity out of it - what they publish and what you get is miles apart. I have never gotten published velocity with any factory ammo - and I have chronographed a lot of it. Even the American Rifleman shows in their tests of guns and ammo that the published data is way over rated. It publicity, salesmanship and voodoo. Smoke and mirrors sells bullets because most guys will believe that they can get the same velocity from their guns and they have no way to test it. It becomes real easy to say that you have a 180 grain Federal 3006 that does 2800 fps when its right there on the box - put it over the chronograph and it becomes real disappointing, real fast.


All:

the pressure to velocity curve is USUALLY a parabolic curve. There are exceptions - I have seen tests that showed a powder getting close to maximum pressure and then with the addition of more powder the pressure dropped and the velocity went up sharply. Its called a pressure knee. In some cases, with some powders, under some conditions you can load to a point just below maximum pressure and then add more for a few tenths or even a few grains before the pressure rises even more sharply than it was doing before hitting the "knee". It is possible to have a load that is overpressure - add more powder that reduces the pressure to safe levels and then reach a point just beyond that where the pressure goes extreme again. Those loads are not published with out warnings like "Use this load exactly as listed. any change in components or load density may cause dangerous pressures." You don't see them as much as you used to - lawyers probably decided it was safer to just keep the loads below the first maximum pressure. These loads occur most often in medium sized cases when using slow double base powders. If you stay with recommended loads and follow the advice they provide you will be fine.

[Black Jaque Janaviac]

The chrony is good for measuring the velocity of your bullets.  That's the simple answer.

The next question is why would you want to know the velocity of your bullets?

A) Two loads may be equally accurate, but is one significantly more powerfull than the other?  You need a chronograph to answer that.

B) This load is inaccurate, but close to what I'm looking for in terms of XXX, what can be done to improve it?  Knowing the velocity or the consistancy of the velocity may help you understand the problem and arrive at a solution more quickly.

Really the chrony is used for load development.  After that, it can stay home.  If you're done developing loads, they're as powerfull and accurate as you want them to be, don't get a chrony.  If you're constantly buying new guns, trying new bullets, testing new powders, then get a chrony.

[qajaq59]

Thank you gentlemen. There has been clear, concise, and well thought out answers to my question about the chronographs and I appreciate the information.

Qajaq59

[PaulS]

If you shoot at ranges that vary from one target to another or from one deer to the next you have to guess at where your bullet will shoot. Even if you can determine the range accurately with a rangefinder unless you know how fast your bullet leaves your gun you have to guess.
With a chronograph I know how fast the bullet is going at 5 yards - that is where I set my screens. With that information and a ballistics program I can figure how fast it was going when it left my barrel. I can also tell you how far it deviates from my line of sight out to what ever range I choose to shoot at. I can get "comfortable" with my bullets trajectory without ever firing beyond two hundred yards. I can find out where to hold if I am shooting up or down slope and how much the wind affects the path of my bullet.

Without the chronograph I would have to spend years of shooting in all those environments, under all the different conditions to get "comfortable" enough with my ammo in my guns to compare with what I can get with the chronograph and a computer in a few afternoons of studying the ballistics sheet.

That and finding out which of the great group producing loads I worked up will give me the highest velocity. That way I can have the accuracy and the highest velocity with it.

At the cost of todays economy chronographs I think every shooter ought to have at least one. For less than you spend on a night out with your favorite lady; dinner, drinks and dancing, you can have a chronograph that will last for years.

[Demonical]

Another beautiful thing about a chronograph is you can use it to shut up a loud mouth!!  :-)

A guy from work bought a brand new Remington Model 700 in 7mmRM and we went shooting. In this case the guy is not actually a loud mouth, but he was certainly mis-informed about what he believed his pet caliber was doing vs the cold reality. See this guy totally believed the 7mm with 162hr (Hornady factory ammo) was shooting 3000fps MV or something like that. We'd have BS sessions around the lunchroom and the 7mmRM was always touted as some marvel of ballistics with vastly superior trajectory to the old .30-06.

On this particular day, I was shooting my "slow-poke" .30-06 with 165gr Hornady BTSP; chrono'd at avg. 2850fps MV.
Well after we had each shot a bunch I asked if I could shoot his 7mmRM and he let me. So I thought, "What the heck..." and decided to fire it through the Chrony to check it out. I have to admit that I did not expect what the Chrony would show...

Long story short the Hornady factory ammo averaged 2780 fps MV!!
Funny thing, the guy was choked!! He did not want to know this at all, but 5 shots through the Chrony left no doubt!!  :eek:

This little session with the chronograph cleared up a lot of BS when we would sit around talking about "flat shooting" calibers. He was a lot more careful not to run down the .30-06 and the 7mmRM got a lot less hype after that!!  :lol:



Edit:
Now of course you can handload a 162gr 7mmRM faster then 2780fps MV but there are a heckuva lotta guys walking around that do not handload, yet still cite data from original 7mmRM load specs that have long since been reduced. The 7mmRM is not loaded to the original specs by any of the major ammo companies anymore.

This is because as ammo companies switched over to testing with piezo pressure equipment the 7mmRM was found to have big pressure spikes, so it's loads got reduced...