Stats for velocities and groups.

[High Desert duck]

So why is a 5 shot the standard for groups but not for velocity?

I’ve been seeing a lot of discussions lately about SD numbers being useless without a large sample size. I agree that the SD may be unreliable with a smaller sample size but I don’t think it is completely worthless.

I use the 5 shot SD/ES number as a reference as to the quality of my load, the same as I use a 5 shot group. For taking a detailed look at average speed and ES/SD of my load I usually do it during drop verification/dope truing, of 15 shots over the chronograph plus a 5 round group (20 total). The SD is usually within 66% of the 5 shot SD. I also do a a 5 shot SD during muzzle velocity checks on each lot of reloading to check the average speed/ group size. (250-600 rounds, this also lets me monitor barre health) I find that these 5 shot groups result in the average speed being +\- 5 to 10 FPS and the SD always around the same.

when I see inexperienced reloaders being told that their 5 shot SD of 7 is meaningless, and you have to have a group size of 25-100 to develop meaningful data I think that is overkill for a guy who is probably here for PRS style shooting, who shoots at most a 10-12 shot string. On the other hand the inexperienced reloader needs to understand his SD isn’t really 7 it’s probably closer to 100-150% of that 5 shot group. I also think of you can consistently get sub 10fps 5 shot SD your reloading practices are probably pretty sound.

sorry for taking up band width I just hate to see a lot of new shooters / new reloaders wasting time and components chasing numbers and developing loads that shoot .25, when once they get around a 1/2 MOA group with a real sub 15 FPS SD (5 shot as of 5-7)They should be practicing, not laying prone in the dirt shooting groups or gathering velocity data.
If load development, shooting tiny groups, or getting an honest SD of less than 5 is your thing that’s cool too. But if your looking for a competitive load for Precision Rifle Matches, stop at 1/2 MOA with a decent SD and go practice.

 

[spife7980]

Because one is what actually is happening and the other is a third party interpretation of one aspect of whats happening?

And the 5 shot replaced the 3 shot. And it has its own limitations just like anything.

Shoot enough and youll realize that none of this is a rule and only a short hand way of getting something that goes boom well and straight.

 

[RldrNewby]

I agree with OP. I’m relatively knew to reloading, <3yrs, and it could be misleading to new shooters/reloaders in that it could be interpreted they are being led to believe their 5 shot data is completely worthless, & that they should be shooting 20-30 round strings, or don’t use Chrono data at all. Statistically speaking, there is certainly some truth in that school of thought as the quality of the stats in a 5 data is obviously less accurate than in 20-30, but I do believe if the 5 shot data looked at in comparative relative terms, the smaller sample sizes can & do have some merit, & is not worthless. It may happen, but I’ve yet to seen a truly rotten Group & SD at 5 shots get totally great at 20-30 shots. On the flip side, I have seen stellar groups & SDs at 5 open some up at 20-30, but never turn completely rotten. There’s a first time for everything, & I may eventually see it, but so far I have not seen that happen. I think smaller data sample sets are totally fine to use for baseline comparisons as long as the Chrono data is NOT being leaned on entirely & exclusively for judging a loads quaility. As long as a quality ladder or OCW is done, & groups & POI are also taken into account along with the small sample size data, I think it’s alright. That’s just my opinion, & in no way do I think anyone else’s opinion is worthless or outright wrong. I think everyone is entitled to their own opinion.

 

[whatsupdoc]

A single 5 shot ES number is not necessarily worthless but it could be a freak and not be repeatable, that is why you record your data so that you may TEST to see if it is repeatable.

I doubt that there any shooters here that can actually shoot a .25 group on command with a bipod and a bag
So chasing that level of accuracy is an impossible dream for most and not necessary for PRS type shooting.

You are correct that practice is #1

 

[nn8734]

Here’s my progression from start to finish.

Note that I’m only considering / weighing SD and ES in any decision during the last step (over 40 rounds); I don’t look at those numbers until I think I have a load recipe ready for production. While this road map is only one of many possible routes that can get a hand loader from A to B, it has worked well for me for over 15 years (practical/prs applications).

Step	What I'm Doing	What I'm Looking For	Notes
1	Initial OCW 3-5 shots per group	Nodes: POI Consistency from Chg Weight to Chg Weight, MV and Pressure Signs	MV Data: Im only looking at MV (not SD or ES) to see what charge weights my min required MV is met and if pressure is present at that MV where POI is consistent from increment to increment
2	Refined OCW 10-15 shots per group, adjacent CWs	POI consistency (repeated from initial OCW), group size at 100m and at 600m	If group sizes are not to my liking but MV and POI consistency is there, I go to seating depth testing in an additional session before going to step 3
3	Final validation - 40-60 rounds	MV Consistency (SD/ES), group size, elevation hold overs at various KDs vs predicted (either via FDAC or ballistic app), overall performance impressions	If SD/ES are reasonable (low double digits, high single digits across 40 rounds im good - i put the load into production. If it all comes apart, i diagnose and re-group (honestly, this very rarely happens)

 

[acudaowner]

yours is way neater than what I had lol
and a far more organized explanation

 

[Dthomas3523]

So why is a 5 shot the standard for groups but not for velocity?

I’ve been seeing a lot of discussions lately about SD numbers being useless without a large sample size. I agree that the SD may be unreliable with a smaller sample size but I don’t think it is completely worthless.

I use the 5 shot SD/ES number as a reference as to the quality of my load, the same as I use a 5 shot group. For taking a detailed look at average speed and ES/SD of my load I usually do it during drop verification/dope truing, of 15 shots over the chronograph plus a 5 round group (20 total). The SD is usually within 66% of the 5 shot SD. I also do a a 5 shot SD during muzzle velocity checks on each lot of reloading to check the average speed/ group size. (250-600 rounds, this also lets me monitor barre health) I find that these 5 shot groups result in the average speed being +\- 5 to 10 FPS and the SD always around the same.

when I see inexperienced reloaders being told that their 5 shot SD of 7 is meaningless, and you have to have a group size of 25-100 to develop meaningful data I think that is overkill for a guy who is probably here for PRS style shooting, who shoots at most a 10-12 shot string. On the other hand the inexperienced reloader needs to understand his SD isn’t really 7 it’s probably closer to 100-150% of that 5 shot group. I also think of you can consistently get sub 10fps 5 shot SD your reloading practices are probably pretty sound.

sorry for taking up band width I just hate to see a lot of new shooters / new reloaders wasting time and components chasing numbers and developing loads that shoot .25, when once they get around a 1/2 MOA group with a real sub 15 FPS SD (5 shot as of 5-7)They should be practicing, not laying prone in the dirt shooting groups or gathering velocity data.
If load development, shooting tiny groups, or getting an honest SD of less than 5 is your thing that’s cool too. But if your looking for a competitive load for Precision Rifle Matches, stop at 1/2 MOA with a decent SD and go practice.

No one is advocating that people go out and shoot 30 round volleys and that you absolutely must know what your real SD are.

What we are saying is not to lie to yourself. You get nothing out of thinking you have a 3sd and a .2 rifle.

We are also saying that if anything, people should spend less time at the loading bench.

You’re far better off spending 1hr picking a speed and prepping brass/powder/seating as consistently as possible than 5hrs with a load development process that literally doesn’t work and is just a creative way to pick a random charge.

Being honest with yourself doesn’t just end with skill level at the practice range. It extends to the loading room and your expectation of your ammo.

 

[Dthomas3523]

Also, a 5 shot group is likely not enough to know what the rifle/shooter is capable off. That fallacy just hasn’t been debated as much.

 

[Tokay444]

@Ledzep will tell you your 5 shot group isn’t indicative of the true performance of that load also. Same as he will for 5 shot ES. The data he presents is also hard to argue.

 

[spife7980]

Agreed, but in the search for something that shoots well once it leaves the barrel actual proof of where the bullet went down range is way more valuable to me than something that scanned one variable on its way out.

 

[Newbie2020]

The problem w the 5-shot sd is when guys compare the mean and sd of one load to the mean sd of another. For that purpose the 5-shot group is (almost) worthless

 

[nn8734]

The problem w the 5-shot sd is when guys compare the mean and sd of one load to the mean sd of another. For that purpose the 5-shot group is (almost) worthless

Yep, and that’s why I recommend that new reloaders (especially those who are stuck on that 5-shot SD-is-meaningful paradigm) leave their chronos at home when shooting those first test groups, looking only at POI patterns and overpressure signs.

Bad/invalid information is worse than no information at all when it comes to SD/ES in that first round of T&E.

 

[Ledzep]

So why is a 5 shot the standard for groups but not for velocity?

I’ve been seeing a lot of discussions lately about SD numbers being useless without a large sample size. I agree that the SD may be unreliable with a smaller sample size but I don’t think it is completely worthless.

I use the 5 shot SD/ES number as a reference as to the quality of my load, the same as I use a 5 shot group. For taking a detailed look at average speed and ES/SD of my load I usually do it during drop verification/dope truing, of 15 shots over the chronograph plus a 5 round group (20 total). The SD is usually within 66% of the 5 shot SD. I also do a a 5 shot SD during muzzle velocity checks on each lot of reloading to check the average speed/ group size. (250-600 rounds, this also lets me monitor barre health) I find that these 5 shot groups result in the average speed being +\- 5 to 10 FPS and the SD always around the same.

when I see inexperienced reloaders being told that their 5 shot SD of 7 is meaningless, and you have to have a group size of 25-100 to develop meaningful data I think that is overkill for a guy who is probably here for PRS style shooting, who shoots at most a 10-12 shot string. On the other hand the inexperienced reloader needs to understand his SD isn’t really 7 it’s probably closer to 100-150% of that 5 shot group. I also think of you can consistently get sub 10fps 5 shot SD your reloading practices are probably pretty sound.

sorry for taking up band width I just hate to see a lot of new shooters / new reloaders wasting time and components chasing numbers and developing loads that shoot .25, when once they get around a 1/2 MOA group with a real sub 15 FPS SD (5 shot as of 5-7)They should be practicing, not laying prone in the dirt shooting groups or gathering velocity data.
If load development, shooting tiny groups, or getting an honest SD of less than 5 is your thing that’s cool too. But if your looking for a competitive load for Precision Rifle Matches, stop at 1/2 MOA with a decent SD and go practice.

There's no BSing the stats or data. But at the same time.. not everyone NEEDS the data either. It just depends on how serious you are trying to be. If you are trying to quantify and decide if one load is better than another, then you need 20+ shots per of each. If you are serious about wanting to know what the SD of your load is to apply some statistical analysis to hit probability on effective range or some such.. You need to shoot 20+ over a chrono. If you're trying to shoot PRS/NRL steel plate matches.. You don't.

If you're a new reloader and you shoot a 5-shot string with an SD of 7, you need to understand that the true SD of your ammo could be 5fps or it could be 18fps and a single 5-shot string won't tell you with any confidence where in between you are. If you're a new reloader that shoots 5x 5 shot groups that average 7fps, then you have a good load (for velocity anyway). Also understand that a single 25-shot string of data would've been more concise, and probably would have had an SD greater than 7fps (i.e. 7fps is likely not your true SD).

If you're conducting 5-shot ea. ladder or OCW tests to get THE BEST load your rifle shoots, then you need to pump the brakes, do some statistical analysis, and start shooting 15-20 shots per and widen your horizons.

If you're new to reloading and just want good ammo for cheaper than box ammo, then load 10 and try it. Understand that .5-.8 MOA for 10 shots is acceptable, and don't go down the rabbit hole of trying to find ".25 MOA all day long" because it doesn't exist... If you're going to use applied ballistics and lie about your MV anyway, then don't even buy a chronograph.

ETA: In all seriousness, I pick a load and shoot 10 as a "feeler" and if it looks promising, I'll verify it with a 20 shotter. If 20 shots is <0.85 MOA it's a keeper and I roll on. If it flirts with 1 MOA I might massage it a bit (or say fuck it and live with it), and if it's over 1 MOA I change bullets or powder. Usually "load development" is less than 50 rounds, but at the end of it I have a very solid idea of the capabilities of what I'm dealing with.

 

[High Desert duck]

I agree with OP. I’m relatively knew to reloading, <3yrs, and it could be misleading to new shooters/reloaders in that it could be interpreted they are being led to believe their 5 shot data is completely worthless, & that they should be shooting 20-30 round strings, or don’t use Chrono data at all.

That’s kinda where I was going with this point. I see a lot of comments that seem to reflect the reloader shouldn’t consider any SD numbers without a significant amount of shots. And it is often presented that the shooter should gather this data if not in a consecutive string, at least in one range session.

I think smaller data sample sets are totally fine to use for baseline comparisons as long as the Chrono data is NOT being leaned on entirely & exclusively for judging a loads quality.

As mentioned in other replies the shooter has to know that his 5 shot SD is most likely not as good as it appears. But when considered with all the other numbers we look at when developing loads it is a part of the whole picture.

 

[Dthomas3523]

That’s kinda where I was going with this point. I see a lot of comments that seem to reflect the reloader shouldn’t consider any SD numbers without a significant amount of shots. And it is often presented that the shooter should gather this data if not in a consecutive string, at least in one range session.

As mentioned in other replies the shooter has to know that his 5 shot SD is most likely not as good as it appears. But when considered with all the other numbers we look at when developing loads it is a part of the whole picture.

Except that’s not how it works in the real world.

Telling people to use that data (except to rule out “bad” loads) is the equivalent to feel good participation trophies.

If the data isn’t reliable, it’s not reliable. Just as ledzep said above, your 7sd 5 shot string could be 5sd or 20sd. One of those is terrible. But you’ll have no idea.

You’re trying to beat the math. It’s just not how it is.

 

[Dthomas3523]

It’s far better for a new reloader to be told the truth. That their 5 string is all but worthless except for weeding out the bad.

Then for them to go several years until they realize their loading process isn’t as good as they thought when they learn more and dig deeper.

 

[nn8734]

That’s kinda where I was going with this point. I see a lot of comments that seem to reflect the reloader shouldn’t consider any SD numbers without a significant amount of shots. And it is often presented that the shooter should gather this data if not in a consecutive string, at least in one range session.

As mentioned in other replies the shooter has to know that his 5 shot SD is most likely not as good as it appears. But when considered with all the other numbers we look at when developing loads it is a part of the whole picture.

Five shot SD/ES: let it go.

It should not be apart of any reloading “picture” to consider.

it’s worthless information (actually it’s worth is negative).

All it does is mislead you with the end result being wasted time, money and components not to mention frustration.

But you and @RldrNewby (apt user name in this context) seem bound and determined to die on that hill so I guess you’re both going to learn the hard way.

 

[Dthomas3523]

Also, real load development isn’t a one and done in a single day.

It’s done for the life of the entire barrel.

All this single day, shortcut shit is typically found in the prs/practical type community. Our targets are big enough you can load up most anything that’s halfway consistent and do just fine.

But, for some reason, people want to still feel like they are actually developing a load. And they want it quick. That doesn’t work. And that’s why if you’re not going to do it right, just load ammo and go. You’ll be fine.

But don’t lie to yourself.

 

[High Desert duck]

There's no BSing the stats or data. But at the same time.. not everyone NEEDS the data either. It just depends on how serious you are trying to be. If you are trying to quantify and decide if one load is better than another, then you need 20+ shots per of each. If you are serious about wanting to know what the SD of your load is to apply some statistical analysis to hit probability on effective range or some such.. You need to shoot 20+ over a chrono. If you're trying to shoot PRS/NRL steel plate matches.. You don't.

If you're a new reloader and you shoot a 5-shot string with an SD of 7, you need to understand that the true SD of your ammo could be 5fps or it could be 18fps and a single 5-shot string won't tell you with any confidence where in between you are. If you're a new reloader that shoots 5x 5 shot groups that average 7fps, then you have a good load (for velocity anyway). Also understand that a single 25-shot string of data would've been more concise, and probably would have had an SD greater than 7fps (i.e. 7fps is likely not your true SD).

If you're conducting 5-shot ea. ladder or OCW tests to get THE BEST load your rifle shoots, then you need to pump the brakes, do some statistical analysis, and start shooting 15-20 shots per and widen your horizons.

If you're new to reloading and just want good ammo for cheaper than box ammo, then load 10 and try it. Understand that .5-.8 MOA for 10 shots is acceptable, and don't go down the rabbit hole of trying to find ".25 MOA all day long" because it doesn't exist... If you're going to use applied ballistics and lie about your MV anyway, then don't even buy a chronograph.

ETA: In all seriousness, I pick a load and shoot 10 as a "feeler" and if it looks promising, I'll verify it with a 20 shotter. If 20 shots is <0.85 MOA it's a keeper and I roll on. If it flirts with 1 MOA I might massage it a bit (or say fuck it and live with it), and if it's over 1 MOA I change bullets or powder. Usually "load development" is less than 50 rounds, but at the end of it I have a very solid idea of the capabilities of what I'm dealing with.

Wow. Lotta good stuff there. I especially like the short load work up and the not worrying about the .25 group. I’m a get the group to about a 1/2 MOA and go practice guy.

 

[High Desert duck]

Also, real load development isn’t a one and done in a single day.

It’s done for the life of the entire barrel.

All this single day, shortcut shit is typically found in the prs/practical type community. Our targets are big enough you can load up most anything that’s halfway consistent and do just fine.

But, for some reason, people want to still feel like they are actually developing a load. And they want it quick. That doesn’t work. And that’s why if you’re not going to do it right, just load ammo and go. You’ll be fine.

But don’t lie to yourself.

In a world of finite time and resources sometimes short cuts and good enough has to suffice, especially when the end goal is practical type shooting.

I just think a lot of the shooters I see at our range that have the goal to shoot our club matches, see things on the inter webs that they have to fully develop a load or they won’t hit anything waste time and put off competing running multiple strings to proof a load that is perfectly capable of hitting our 2 MOA target at 600 yards.

Also, just for the record, once I have settled on my load I do run a 20 shot string (2 consecutive 10 shots) to look at the avg velocity, SD, and ES.

 

[Newbie2020]

In a world of finite time and resources sometimes short cuts and good enough has to suffice,

@Dthomas3523 has given plenty of useful shortcuts; however, as @Ledzep has repeatedly hammered:a 5 shot sd is a lie.

It is worse than useless; it is most likely misleading. You literally are better off Loading and shooting groups for group size without a chronograph than looking at the 5-shot sd.

There’s a shortcut: if there isn’t time to develop a proper sd just pick a charge for desired mv, tune group size using seating depth, and go shoot.

Wait, @Dthomas3523 has been saying that all along! Haha

 

[High Desert duck]

@Dthomas3523 has given plenty of useful shortcuts; however, as @Ledzep has repeatedly hammered:a 5 shot sd is a lie.

It is worse than useless; it is most likely misleading. You literally are better off Loading and shooting groups for group size without a chronograph than looking at the 5-shot sd.

There’s a shortcut: if there isn’t time to develop a proper sd just pick a charge for desired mv, tune group size using seating depth, and go shoot.

Wait, @Dthomas3523 has been saying that all along! Haha

I am not personally looking to load for a 5 shot SD. When I use a 5 shot SD, it is only to eliminate a load. It has mislead me before but very rarely. When it has it gets discovered during my final step.
either way can we agree that many shooters would benefit from an extra 50 rounds of focused practice with the shortcut load than 50 shots laying prone or off The bench looking for the perfect load?

edited because of spell check

 

[RldrNewby]

Five shot SD/ES: let it go.

It should not be apart of any reloading “picture” to consider.

it’s worthless information (actually it’s worth is negative).

All it does is mislead you with the end result being wasted time, money and components not to mention frustration.

But you and @RldrNewby (apt user name in this context) seem bound and determined to die on that hill so I guess you’re both going to learn the hard way.

You are correct. It can get mighty lonely on the hill, but I have thick skin, so your insults don’t bother me.

I respect your opinion, but I have my own too, and I’m just as entitled to mine as you are of yours. Yes, I am new to reloading, and yes I have learned tons of awesome stuff from more experienced ppl on here, you included.

FWIW, I have taken two of my load development’s into the 20+ count range on the chrono, and true enough, I wasn’t sub 10 on the SD, and I never thought I would be based off a couple 5 round groups. I wasn’t far off tho, low teens if I remember right. Barrel temps came into play, and I do remember breaking the data down afterwards into segments. If I remember correctly, the SD numbers in the first part, when the barrel was cool looked awesome, then then they opened up considerably more towards the end as the barrel got hot. In essence one could argue that data was garbage too, bc I didn’t control my barrel temp & shooting pace correctly. Yet, the larger volume data still gave me relative useful info, just like the 5 shot group did. The 20 string told me something. It said I had a decent load with a cooler barrel, & I can expect my SDs to grow as my barrel heats up. Awesome experiment. I loved it.

I was never saying don’t use large volumes of data over small. Ultimately, I do agree that larger volumes of data are statistically more accurate. I also agree with other folks that it’s really important for newbies like me to realize and make the distinction that what we get on a few 5 shot groups is NOT our real SDs. Does that mean I’m gonna shoot 20rounds or more at each varying incremental charge weights during load development? Probably not. Maybe one day I’ll change my process into doing that, but for now, I’ll stick to small volumes of data to save components & barrel life.

I do think I will adopt someone’s suggestion to only use the Chrono in the beginning to verify I’m in the velocity area I’m wanting to load for, but then leave the Chrono out of the picture entirely until I’m at final load verification at the end. This would be to gather data over practical shooting pace to plug into my ballistics app. At that time, 20 rounds or more will be ideal if I’m understanding correctly, and I have no problem with doing that.

 

[nn8734]

You are correct. It can get mighty lonely on the hill, but I have thick skin, so your insults don’t bother me.

I respect your opinion, but I have my own too, and I’m just as entitled to mine as you are of yours. Yes, I am new to reloading, and yes I have learned tons of awesome stuff from more experienced ppl on here, you included.

FWIW, I have taken two of my load development’s into the 20+ count range on the chrono, and true enough, I wasn’t sub 10 on the SD, and I never thought I would be based off a couple 5 round groups. I wasn’t far off tho, low teens if I remember right. Barrel temps came into play, and I do remember breaking the data down afterwards into segments. If I remember correctly, the SD numbers in the first part, when the barrel was cool looked awesome, then then they opened up considerably more towards the end as the barrel got hot. In essence one could argue that data was garbage too, bc I didn’t control my barrel temp & shooting pace correctly. Yet, the larger volume data still gave me relative useful info, just like the 5 shot group did. The 20 string told me something. It said I had a decent load with a cooler barrel, & I can expect my SDs to grow as my barrel heats up. Awesome experiment. I loved it.

I was never saying don’t use large volumes of data over small. Ultimately, I do agree that larger volumes of data are statistically more accurate. I also agree with other folks that it’s really important for newbies like me to realize and make the distinction that what we get on a few 5 shot groups is NOT our real SDs. Does that mean I’m gonna shoot 20rounds or more at each varying incremental charge weights during load development? Probably not. Maybe one day I’ll change my process into doing that, but for now, I’ll stick to small volumes of data to save components & barrel life.

I do think I will adopt someone’s suggestion to only use the Chrono in the beginning to verify I’m in the velocity area I’m wanting to load for, but then leave the Chrono out of the picture entirely until I’m at final load verification at the end. This would be to gather data over practical shooting pace to plug into my ballistics app. At that time, 20 rounds or more will be ideal if I’m understanding correctly, and I have no problem with doing that.

Knowing how and when in the development process to rely on SD to fine tune your otherwise GTG load is the main idea. It’s what I and others have been trying to tell you all along. You do get there in your last paragraph above (looking only at MV in the beginning; SD/ES over 20-30 rounds when you think you have a prod-ready load at the end of the development cycle)

You likely first saw this approach in post 5.

If insulting you finally got through, redirecting you away from the myth that SD/ES using tiny sample sizes early in testing was meaningful and got you on the right track going forward then I’d say the winner of this back-forth exchange is you.

 

[Dthomas3523]

You are correct. It can get mighty lonely on the hill, but I have thick skin, so your insults don’t bother me.

I respect your opinion, but I have my own too, and I’m just as entitled to mine as you are of yours. Yes, I am new to reloading, and yes I have learned tons of awesome stuff from more experienced ppl on here, you included.

FWIW, I have taken two of my load development’s into the 20+ count range on the chrono, and true enough, I wasn’t sub 10 on the SD, and I never thought I would be based off a couple 5 round groups. I wasn’t far off tho, low teens if I remember right. Barrel temps came into play, and I do remember breaking the data down afterwards into segments. If I remember correctly, the SD numbers in the first part, when the barrel was cool looked awesome, then then they opened up considerably more towards the end as the barrel got hot. In essence one could argue that data was garbage too, bc I didn’t control my barrel temp & shooting pace correctly. Yet, the larger volume data still gave me relative useful info, just like the 5 shot group did. The 20 string told me something. It said I had a decent load with a cooler barrel, & I can expect my SDs to grow as my barrel heats up. Awesome experiment. I loved it.

I was never saying don’t use large volumes of data over small. Ultimately, I do agree that larger volumes of data are statistically more accurate. I also agree with other folks that it’s really important for newbies like me to realize and make the distinction that what we get on a few 5 shot groups is NOT our real SDs. Does that mean I’m gonna shoot 20rounds or more at each varying incremental charge weights during load development? Probably not. Maybe one day I’ll change my process into doing that, but for now, I’ll stick to small volumes of data to save components & barrel life.

I do think I will adopt someone’s suggestion to only use the Chrono in the beginning to verify I’m in the velocity area I’m wanting to load for, but then leave the Chrono out of the picture entirely until I’m at final load verification at the end. This would be to gather data over practical shooting pace to plug into my ballistics app. At that time, 20 rounds or more will be ideal if I’m understanding correctly, and I have no problem with doing that.

Barrel temp typically only affects things if the round is left in the chamber and is allowed to heat up. Otherwise, it doesn’t do much. This is a common misconception people have and lead them to not realize their process is off a little.

As an example, these were shot as fast as I could run them:

 

[RldrNewby]

Barrel temp typically only affects things if the round is left in the chamber and is allowed to heat up. Otherwise, it doesn’t do much. This is a common misconception people have and lead them to not realize their process is off a little.

As an example, these were shot as fast as I could run them:

View attachment 7665073

Gaw…Those are great numbers! Did not know that on the barrel temp. Takes me a little while to settle on the rear bag and go over my form before squeezing off the each shot. Maybe I was taking too long while the rounds in the chamber were heating up as the string progressed. Who knows. Shootin a stock barrel, nothing fancy, & my round count is getting crazy high. Right at 3,000 rounds. Any recommendations on replacement? Thinking Bartelin, but open to suggestions.

 

[Dthomas3523]

Gaw…Those are great numbers! Did not know that on the barrel temp. Takes me a little while to settle on the rear bag and go over my form before squeezing off the each shot. Maybe I was taking too long while the rounds in the chamber were heating up as the string progressed. Who knows. Shootin a stock barrel, nothing fancy, & my round count is getting crazy high. Right at 3,000 rounds. Any recommendations on replacement? Thinking Bartelin, but open to suggestions.

With the way things are currently, whatever barrel you can find. Any of the reputable companies are good barrels.

If not letting barrel cool, get everything set snd ready before chambering. Then chamber and fire quickly. If you end up having to take time to mess with rear bag and such, eject the round from the chamber and let it cool off. Move to another round that isn’t hot.

 

[Doom]

I recently put together some data to demonstrate just how small sample sizes can be terribly misleading, and to show how what the data actually predicts.

Understand that 3,5, and even 10 round sample statistics, average and standard deviation, tell you about the samples, not the larger population of rounds that are of interest. Predicting what the sample says about a larger population is a probability problem and requires more analysis that just the mean and standard deviation spit out about the Sample (chronograph data).

The graphs below show an analysis of some chronograph data taken recently. Its Blazer 22LR 40gr ammunition and real data. Sample one is a ten shot group with a average velocity of 1184 fps and a standard deviation of 21 fps. ES was 71. Samples 2, 3, and 4 are random 3 shot samples of the ten rounds of group 1. Samples 5 and 6 are rand 5 shot groups of data from group 1. No data is duplicated in the three different three shot or in the two five shot groups. These are not the only combinations of data possible. The bars reference the confidence intervals for each set of data to give a 95% probability that the true velocity and standard deviation lies within that range. You can see that the three shot groups were not nearly representative of the population they came from and that the confidence intervals are quite large. The five shot groups are closer to the average but the range for the standard deviation are still larger than the population.

So what about the ten shot group? That ten shot group predicts that the true average velocity of a larger population of shots from that lot of ammunition should be between 1170 and 1200 fps with 95% confidence and the standard deviation is between 14.5 and 38.4 fps.

One thing I discovered a when I first started using a chronograph. I can develop a load without it, but even with it I can't develop a load without the target!

 

[Doom]

Barrel temp typically only affects things if the round is left in the chamber and is allowed to heat up. Otherwise, it doesn’t do much. This is a common misconception people have and lead them to not realize their process is off a little.

As an example, these were shot as fast as I could run them:

View attachment 7665073

That 31 round sample gives a 95% confidence interval for velocity of 2805.1 to 2808.9 fps and a SD confidence interval of 4.2 to 7 fps. Pretty darn good!