How many rounds do you chronograph?

[R Reed]

When working up a load, how many rounds do you actually chronograph per charge weight to get your AVG, ES, SD.

Been reading a lot of interesting stuff in relation to ES/SD and the statistics of how many rounds you need to fire/chronograph to have data that you can consider dependable. But my question was more, what are we actually doing right in practice, not theory. I allowed 2 choices so that if people have different standard for pistol or rifle, or training vs precisions ammo and you have different methods you can list both.

For general purpose training loads and handgun loads I am generally shooting 10, for my precision/target ammo I am shooting 30.

 

[Bearded Phil]

At least 10 per charge and then I sometimes run the same ladder again on another day to see if there's correlation.

 

[GoldieMI]

for my PRS rifle- which is the same load (until this lot of powder runs out)
30.6 Grains of Varget with the same 105 Grain Berger Hybrids/Remington 7.5s/Lapua Brass
I chronograph every firing outside of the actual competition, so all practice rounds, all sight in rounds, and all fouling rounds.

 

[Blue68f100]

For a quick screening, I do 3/per charge. Once I find those promising loads I load a larger batch to test, min 10. If good I will load 50 to confirm it was not fluke.

 

[Smokin Gator]

I usually test about 10 rounds. This is for handguns in USPSA. I'd do more testing if I was shooting long range rifle.

 

[Kaldor]

5, but I run that 5 round test multiple times so I can look back and see if the numbers jive with previous range trips. So in total, for a load that I consider worth loading? Probably close to 20 rounds.

 

[sqlbullet]

Not enough for a statistically significant sample

I am not a precision shooter. My goal is to ensure that I fall in a safe pressure level and have consistent reloading practices. As long as my SD is good and velocity averages to an expected range I call it good.

 

[Lennyjoe]

I start with 5.

Phase 1 is accuracy and pressure. Once I find an accurate load I’ll run more tests to include moving OAL closer to lands and find the sweet spot.

ES and SD are evaluated during phase 2.

 

[GeoDudeFlorida]

One to verify the powder charge is giving the expected velocity.
If it is, then I Chrony two more: one powder forward and one powder back to verify the charge is relatively position insensitive.
If it is not position sensitive and the velocity of each round was in the expected velocity window for whatever I want the bullet to do, I’m done. I will typically empty the cylinder/magazine if I loaded more than three but, with a single shot, I’m done.
If there’s more space between the velocity of the three tests than I can finagle in the field, point shooting game, the load is a loser and I scrap it. No sense wasting time trying to tune a load that’s position sensitive.

Keep in mind long before I break out the Chrony I’ve shot a few test rounds checking for POA~POI, proper feed/extraction, feel, flash, consistency on target, and whether or not I can replace the components if it works well. No sense building up a new load without supplies on-hand.

 

[Laphroaig]

Ever since I got my Garmin I chrono as many as I shoot. I even set it up when i decock my crossbow, 1 shot. It's all data.

I do the best that I can with every load depending on the expectation that I have, and to me the statistics are just a validation of my process not a goal in itself. Judging from the metric that the ES should be at least 4x the SD to be statistically significant it takes about 25 shots to get there.

5 shots probably gets me close enough for an average velocity to run trajectory calculations.

 

[Maintenancan8193]

For a quick screening, I do 3/per charge. Once I find those promising loads I load a larger batch to test, min 10. If good I will load 50 to confirm it was not fluke.

I pretty much do the same thing , but I start with 5 rds

 

[ParallelCode]

For a quick screening, I do 3/per charge. Once I find those promising loads I load a larger batch to test, min 10. If good I will load 50 to confirm it was not fluke.

This matches my approach.

 

[marchboom]

For a quick screening, I do 3/per charge. Once I find those promising loads I load a larger batch to test, min 10. If good I will load 50 to confirm it was not fluke.

I agree except I shoot 5 rounds. But his method is correct, IMO. Preliminary testing will indicate if the combination has promise. If so then load up more of that load and verify it was not a fluke.

 

[Charlie98]

For a quick screening, I do 3/per charge.

Same here, at least for rifle. In the end, if the velocity is where I think it needs to be, then I continue on with accuracy testing. If the load meets my accuracy requirements, I'll run another batch... 5, 10... to get my next set of chrono readings, and ES, but that is just data to look at... if the load is showing the accuracy I want, I don't really care about the absolute numbers, other than it's moving along fast enough.

Pistols are the same, but I usually run 10, because pistol or revolver velocities can vary a lot more. Same method, however... if it meets my expectation of velocity, then I move on to accuracy, etc, etc.

 

[GeoDudeFlorida]

Same here, at least for rifle. In the end, if the velocity is where I think it needs to be, then I continue on with accuracy testing. If the load meets my accuracy requirements, I'll run another batch... 5, 10... to get my next set of chrono readings, and ES, but that is just data to look at... if the load is showing the accuracy I want, I don't really care about the absolute numbers, other than it's moving along fast enough.

Pistols are the same, but I usually run 10, because pistol or revolver velocities can vary a lot more. Same method, however... if it meets my expectation of velocity, then I move on to accuracy, etc, etc.

I do the opposite, sorta. If it hits where I’m looking and feels right, then I double check the velocity by getting numbers.

 

[AJC1]

Now that I have a Garmin, I crono every shot, because it's easy and more data makes more informed decisions....
For testing I investigate with 5 shot strings and evaluate 10 or more strings....

 

[bluetopper]

I work up a load using repeatable accuracy as a guide. When I'm happy with that I may check the velocity 3-4 times just for heck of it.

 

[Rimfire McNutjob]

Is there a hidden bias in this data? Are the 5 shot guys very often shooting revolvers by chance?

 

[.45Coltguy]

Hmmm. I'm not shooting long distance or in any type of competition. So, when comparing accuracy with SD, its like comparing asphalt to trout.
Somewhat higher SD, but, accuracy is good, I don't pay attention to the higher SD numbers. Long distance shooters, it probably does matter.

Edit: Opps, forgot to add the number of shots. 7 per load till I find the load.

 

[jmorris]

Depends on what I am doing but I have worked up loads before moving up in charge weight with just one round (that failed to meet or exceed powerfactor) being fired before an adjustment.

Worked up loads for a number of different bullets and powders, in a fraction of the time it takes to load at home, test, then pull the remaining rounds and repeat. Not even close, minutes vs days.

 

[Targa]

5 for me.

 

[Horskinator]

I run a pressure test (10 rounds starting at book over max and then backwards at a predetermined interval) I shoot from lowest load forward until complete or pressure signs. I used this data to see if I catch a window where velocities are close between shoots, typically less than 10fps. I usually find 2. I then work the higher velocity pair by splitting the charge between the two that were close and will work 5 rounds at that charge to check SD and velocity. This is usually a good and consistent load to sight in the rifle on. Then I will chrono every practice round of this load to verify it is stable and this is done in batches of 5-10 usually depending on caliber. I am a hunter so the variables on the shooting days for wind, time, and temp will tell me I have a solid and stable load so that I load 40+ with new brass from the same lot to be used only for hunting. This system has worked well for me so far but will probably not work for the long range guys.

 

[Charlie98]

I do the opposite, sorta. If it hits where I’m looking and feels right, then I double check the velocity by getting numbers.

Well, I have an expectation of velocity with my loads. An accurate load that only goes 2000fps in .308 isn't going to do me a whole lot of good shooting at distance... so. first things first, let's see what the velocity is.

 

[.38 Special]

All of them. Once the chronograph is set up - I'm still clinging to my old Oehler, with sky screens and tripods and cables everywhere - I might as as well use it.

But I'm also not a "precision" rifleman. I use the chronograph to ensure that I'm not way above expected velocities - I do hate blowing myself up - and to eliminate any loads with with really awful ES. Otherwise, once I've got my desired velocity, acceptable accuracy, and no terrible numbers from the chronograph, I'm done.

 

[MikeInOr]

If a load groups well then I only check the velocity to look for over pressure signs.

If I am having a hard time finding a load that groups well for a particular rifle I will start running them over the chrony to see if the issue is related to velocity variations.

I don't look for problems (velocity variations) where none exist (the load groups well).