[mugsie]

I can understand how a chrony will help me determine the pressure since it's a factor of speed, and I can understand how it will help in finding the most consistant load (but I should be doing this anyway since I measure all the loads), but group sizes? Isn't the group size a factor of the barrel resonance? I can't see where a chronograph will help me determine where the tightest groups will be.

Before I spend money on something I may not need (another nice toy however), can someone explain how these two correlate? thanks...

[ranger335v]

It doesn't. Not meant to, it gives the speed, period. Groups are found on the target.

[sitedzn]

Depends on what you're looking to do. I need to chrony my loads to ensure I'm maintaining velocity downrange at 1000 yds. I can shoot a great group (0.3" @ 100yd) with 2400fps, but that translates to below M1 @ 1000 - hence my accuracy goes WAY down that far out.

[45ACPUSER]

Pressure is not equated to velocity. There is no safe way to interpolate such nonsense! Each bbl / chamber is a law unto itself!
I take results on the target long before velocity. Once I have a load worked up and verified at longer ranges. I then chrono the load so I can make a bullet drop chart. You can go nutz looking at the numbers!

Of course for LR shooter the better the #'s look the less dispersion at longer ranges. Of course a person needs to meet various needs to ensure a bullet choice is going to stay supersonic at say 1K. Like the 30 cal 155 Palma SMK needs to be cooking around 2950 or better to stay supersonic.

[USSR]

mugsie,

IMHO, everybody that reloads for rifles should have or have use of a chronograph. While it has no bearing on group sizes, it does help you in developing safe loads at suitable speed which give low ES/SD numbers.

Don

[snuffy]

Pressure is not equated to velocity. There is no safe way to interpolate such nonsense!

While there is no chart with a direct pressure/velocity relationship from chronograph readings, it can tell you when your particular load combo has reached it's pressure limit.

You choose a bullet for it's intended purpose, whether it be for target or hunting. You then choose a powder from a list in whatever manual you have. Same for the primer. Starting at recommended starting loads, you work up to listed max. The chronograph should show you a steady increase in velocity as you go up to max. If, however, it shows less gain as it nears max powder charge, you are running into excess pressure. The readings can even reverse, less velocity for more powder.

As for how it relates to improved accuracy, it can tell you something is wrong with your chosen load. Vast disparity in extreme spreads say that something is wrong with that load or rifle somewhere. That load may print a small group at short range, but it will vertically string at long range.

[Hunter0924]

Consistency=accuracy.

[RugerOldArmy]

Yep, Hunter got it.

(Although consistency is precision. Accuracy is when you've adjusted your scope and hit what you intended. )

Chrono's can show the extreme spread and standard deviation between various loads in a batch, or perhaps, in different temperature conditions.

[esq_stu]

Consistency=accuracy.Exactly. If every round is the same velocity, that's one major variable eliminated - one of the most controllable in reloading. If you see a wide variation in velocities, find the causes - charge weight, seating depth, case dimensional variations, etc. As you eliminate the variations, the variation in velocity should get smaller and smaller. This does nothing for other problems, like bullet design, condition of the bore, etc. But repeatable velocity is key.

[quicktime]

In testing for long range stuff you might want to sacrifice a little bit of overall speed for consistancy. I have seen where a tenth of a grain of powder will start acting up and give you a big spread in velocity. We always test new barrels and or guns with a variation of powder weights to get the consistancy that wins matches.

[SlamFire1]

A chronograph provides invaluable information. Velocity is something that is very useful to know. When you shoot enough, and chronograph enough, you get a very good database to set your own bullet/velocity limits. It also allows you to see if something unusual is going on with your firearm.

While it is true that pressure and velocity are related, pressure goes up exponentially, while velocity goes up a little. However you can still use velocity readings as a way of telling that a load is way too hot. When a load is going way too fast in a barrel, you better cut your loads for that barrel. There is no free lunch.

Unfortunately there are occasions, when you have a “slow” something, and yet you have positive pressure indications at lower than expected velocities.

As for accuracy, in certain conditions and combinations of powders and calibers, you will get horrific extreme spreads. Like 300 to 400 fps extremes. When you see a condition like that coming over your chronograph, you are unlikely to get good accuracy out of that combination.

I use a chronograph to develop loads. I note the temperature conditions, and all the load data. I also note when I start having pierced or leaking primers, or stiff extraction. I have a decent enough database that I have an idea of what the limits are in my firearms. And I am able to compare velocity versus accuracy between loads. Mostly I keep my velocities within factory manual limits and seldom have a problem.