do i really need a chrono?

[thump_rrr]

It depends, if you are the average reloader that only uses loads found in a reloading manual, and your rifle and cartridge components match those used by the developers of the reloading manual, then no.

On the other hand, if you want to develop a precision load a combination of cartridge components not listed in any manual then yes, you need to use a chronograph.

Most people that reload are just that, reloaders, others are what I call hand loaders, they are the guys that will go where ever the testing points them. These are the people that need a chronograph. These guys will use any bullet, case, primer, and powder combination that produces the results that they are looking for, even if that component combination isn't listed in any manual...and that can cause problems that a chronograph can warn you about. A good example is the fact that most reloaders don't realize that bullets of the same weight and general shape from different manufacturers don't produce the same speeds or pressures. Using a Sierra load recommendation with Hornady bullets will most likely produce higher pressures and faster speeds than the Sierra manual lists. That wont mean much for most people because they are well within the range of safe loads, but if you might want to be aware of the difference in pressures and speeds if you are working on a 300 Win Mag for 1100 yard targets.

A chronograph will also help develop a bullet drop table that you can use as a basis for estimated bullet drops at various ranges. Without the chronograph you can't really know what the muzzle velocity is and you will only be guessing at how much drop you have a various ranges, that's real problem is you ever want to work on your medium to long range shooting skills.

I disagree with the last paragraph which I emphasized with bold type.

These days with ballistic calculators available on our computers, tablets and smartphones it is no longer a necessity.

Let's assume you have a load with an unknown velocity but you can guesstimate it by what reloading manuals tell you.
For example 2650 ft/s

You plug all your data into the ballistic calculator including your zero distance.
You then shoot at a second known distance. Example 500y
You use the estimated drop from the calculator to get you close.
For example 10.5 moa.

You take several shots and you see you are shooting 5" high.
You dial down one additional MOA. You take several more shots and confirm you are hitting dead center.
You know that you have dialed a total of 11.5 MOA.
You use the trueing feature of the ballistic calculator to tell it that at 500y your actual drop is 11.5moa and it will come up with an accurate ballistic table and your muzzle velocity.
As long as you have 2 points on a curve the rest will fall into into place.

The most important thing to remember is that if you put garbage in you get garbage out.

Don't get me wrong I have a chronograph and I use it often but there are many ways to skin a cat.

 

[thump_rrr]

Don't have one, don't have anywhere I could use one - I mostly shoot at local indoor gun shop ranges where they would be impossible to setup or use.

I use my Chrony with the LED lamps indoors at my local range quite often.
There are others using the CED with LED lamps also.
The fluorescent lighting wreaks havoc on the chronograph if you don't use LED lamps.

 

[guzzi]

How would I know what size hole a 30-06 would make in a metal target 10 feet away if I didn't have a chrony?

And, how you you know the destructive force of a 357 magnum if you don't shoot your chrono?

By the way, it still works with holes in it.

 

[thump_rrr]

We should probably take this off thread ....

Explain the science of why it is false?

Secondly, explain to me why reloading manuals use velocity as a guide to safe loads where being within pressure limits = safe. If your assumption is correct then the quoted velocity in manuals has no relationship to pressure and therefore why bother to quote the velocity, just give us the powder charge and COL and be done with it.

Cheers

The quoted velocity in reloading manuals is accurate because that was a measured output.
They are also measuring pressure via a strain gauge.

When you translate their findings to your firearm you need to make some assumptions.

Assumption #1 Your lot of powder is the same as their lot of powder.
Assumption #2 Your brass has the same internal volume as their brass.
Assumption #3 Your primers are the same as their primers.
Assumption #4 Your bullets are of the same physical dimensions and weight as theirs
(I have 2 500 count boxes of 175gr Sierra Matchkings who's base to ogive lengths are 0.020" apart)
Assumption #5 You are loading to the same length
Assumption #6 You have the same freebore.
Assumption #7 You have the same type of rifling
Assumption #8 You have the same twist rate
Assumption #9 You have the same barrel length
Assumption #10 You are shooting at the same altitude with the same climatic conditions.

Some are more important than others but add every single factor together and you can end up quite a ways away from what the manual states.

 

[j1]

J1

No!

 

[spitballer]

when the chrony shows a velocity increase, you can be assured the pressure is also increasing...

I'm not so sure I buy this. Increasing duration can raise velocity without a corresponding increase in pressure. Obviously at some point the increased spin will cause plugging, but determining the point at which this happens is fairly easy with the help of a chrony.

 

[murf]

spitballer,

i think the only way to increase duration (i'm assuming of the pressure curve here) is to increase the initial internal volume of the case, or change to a slower burn rate powder. my comment was intended for those shooting identical loads varying only by amount of powder (as when one works up a load).

murf

 

[Andrew Leigh]

The quoted velocity in reloading manuals is accurate because that was a measured output.
They are also measuring pressure via a strain gauge.

When you translate their findings to your firearm you need to make some assumptions.

Assumption #1 Your lot of powder is the same as their lot of powder.
Assumption #2 Your brass has the same internal volume as their brass.
Assumption #3 Your primers are the same as their primers.
Assumption #4 Your bullets are of the same physical dimensions and weight as theirs
(I have 2 500 count boxes of 175gr Sierra Matchkings who's base to ogive lengths are 0.020" apart)
Assumption #5 You are loading to the same length
Assumption #6 You have the same freebore.
Assumption #7 You have the same type of rifling
Assumption #8 You have the same twist rate
Assumption #9 You have the same barrel length
Assumption #10 You are shooting at the same altitude with the same climatic conditions.

Some are more important than others but add every single factor together and you can end up quite a ways away from what the manual states.

OK let's start again.

Typically we treat every calibre and load differently.

So we start by assuming a safe load for a given set of components and we chrony the speed. Then for the same given components and dimensions we can safely assume that in 98% of the cases that for every increment in velocity there will be the commensurate increase in pressure. What other measure does the man in the street have to associate chamber pressure with. We do not then apply the same pressure curve to a different set of components. So my point was specific to a set of components that speed will be as good an indicator of pressure as anything.

If we then change components, bullet mass, powder etc. we start the process again and we do not apply any data from the previous load.

At least a chrony gives some objectivity, the rest are all rather subjective. Bolt opening, primers etc. A chrony along with a tool like QuickLoad then is very powerful as one gets a very good idea of the internal ballistics based on the numerous manufacturers inputs and measured data.

 

[cfullgraf]

I disagree with the last paragraph which I emphasized with bold type.

These days with ballistic calculators available on our computers, tablets and smartphones it is no longer a necessity.

Let's assume you have a load with an unknown velocity but you can guesstimate it by what reloading manuals tell you.
For example 2650 ft/s

You plug all your data into the ballistic calculator including your zero distance.
You then shoot at a second known distance. Example 500y
You use the estimated drop from the calculator to get you close.
For example 10.5 moa.

You take several shots and you see you are shooting 5" high.
You dial down one additional MOA. You take several more shots and confirm you are hitting dead center.
You know that you have dialed a total of 11.5 MOA.
You use the trueing feature of the ballistic calculator to tell it that at 500y your actual drop is 11.5moa and it will come up with an accurate ballistic table and your muzzle velocity.
As long as you have 2 points on a curve the rest will fall into into place.

The most important thing to remember is that if you put garbage in you get garbage out.

Don't get me wrong I have a chronograph and I use it often but there are many ways to skin a cat.

Yup, one can calculate bullet drop without a chronograph but having access to 500 yard or so ranges is not practical for many.

I think there are too many uncontrolled variables for the average shooter to get reliable results at shorter range differences such as 100 yards and two hundred yards.

I'll agree that it would be nice to be able to verify a ballistic table calculations at long ranges regardless of how the table is generated.

 

[j1]

J1

Still think the answer is NO.

You might like one, but that was not the question.