I am just curious, is there so called acceptable numbers for the es and sd on my 243.
im shooting the 95gr berger hunters, behind h4831sc. I got some good numbers but my best groups are on the bigger spreads and deviations.

my first 3 shot group had an ES 6, and SD of 2 thats the smallest charge good group not great
the second best group and hottest charge had an ES 13, and SD of 7.
The Best group and the third of the four charges i had had an ES 44 and an SD of 20. and that loads makes a nice ragged .294 hole at 100yds. out of a factory barrel remington.
I am very pleased but confused
I sure would have thought the loads with the lower numbers would have shown better results.

Lower spread does not mean more accurate loads. 3 shot groups are realistic to test hunting rounds for groups but trying to get data from them can be inconsistant. When I work up data I shoot 10 rounds slow fire (1 round a minute).

44 fps spread is not bad but could be 2 rounds 5 fps apart and one 40 fps different.

ok I was starting to second guess myself , I am goin to load up some more and sit my self down and shoot some more numbers. I was very happy to see it grouping like it is, i just hope it will repeat when I hit the range again. I guess even if it opens up some it will be a very accurate deer round.

The chrono is a fine tool and should be used by any serious reloaded/shooter. Sometimes the numbers just don't work the way you think or have been told they should. Look at dc math. Use the chrono to check your velocities. But shoot the safe load your rifle likes.

your right I looked at the print out my fps were 2991,2947,2952. any idea what may have caused it to do that

Those sorts of variations are not at all uncommon. Nor do small extreme spreads and Standard Deviations always match up with the best groups. For the velocity numbers to be really meaningful you'll need a bigger sample than one or two three shoot groups. You may be surprised at your group to group variations as well as shot to shot. After you've shot five or more groups (15+ rounds) of the same combo, combine the data and then take a look at your averages and variations. If you get consistently good groups the statistics don't really mean that much.

Hey d-r,

You've already received good advice and I'd just like to add my $0.02.

Yes, I shoot slow when the Chrony's hooked-up because at least 10 shot strings are required to begin to obtain valid data. You require more data than 3 shot "groups" so I don't get too wrapped around the axle with accuracy when the 10 shot strings are being lobbed over the screens to obtain valid data. I pretty much know already the load(s) are delivering the accuracy potential I desire; now I want to know the Rest-of-the-Story or what the numbers are doing.

A minimum of 10 rounds strings slow because barrel heat will play havoc with the results, too. I'll use at least a 3x10 shot strings before I consider the values to be meaningful and better yet over a coupla days since the light source can result in different readings too.

Yes, it's really nice to have low ES's & SD's, but this usually means your loads are about as consistant as they're gonna get, bullet pull, brass fatigue, fouled bores all play havoc (or not?) with the perfect numbers.

I have the display cord to the Chrony marked with tape so I get a proper 10, 12 or 15 ft. to the screens depending on what constraints I have to use at different ranges but at least I know that the distance to the screens are pretty much the same every time. Then there's the light, overcast, sunny, shade, angle of the sun (morning/afternoon) whatever .....

Net, one day you're at 3280 fps and the next time 3260 fps; the truth is somewhere in the middle but now you begin to optimize the "averages". As long as there's not a completely inconsistant 3150 fps for a string - then something's awry.

Just be careful not to send one thru the Chrony, done that and it's spectacular!

I'm going to clean the rifle and go back and shoot a couple foulers, then I will
sit and try running 15 more of my best grouping loads (3 five shot strings) over the chrono and see what my numbers and groups avg out to be. That should give me a good idea of the loads performance. I'm going to keep the rounds in a small cooler to try and duplicate the cold these rounds may have to perform in.

I haven't shot the chrono yet. That would be wild, Dust and plastic allover. I tought I
was going to hit it when I was shooting my goose loads thru it in my 12ga. I was a little nervous about doing that

I like single digit SD, but I'll take up to 15fps or so. If I don't get it I look at my loading and what I may have done wrong, or could do better. For short range hunting I don't get too worked up about it as long as the load shoots at the required range.

The posters are correct about groups, but at longer range large ES will mess with your vertical dispersion. If your rifle has a naroow band of sweet spot you are also at risk with accuracy. I've seen the numbers and they are meaningful at long range and you can check them out on a ballistic calculator. I haven't done it myself and deferred to the smart guys who had doen the maths.

Bear in mind that at really top end loads the ES (and usually the group) will open up. A high ES on a maximum load is a warning sign to me to throttle back. I'm not saying it is the case here. THe velocity seems reasonable for a 95gr and your higher load had a narrower SD. All data also needs to be confirmed again if you really want to rely on it. Lastly, if you get a bum number mark that case or put it in a specific spot in your ammo box and check it again.

Ok. The crazy part is that my second of the four charges had huge spread, like 92fps. All 3 rounds were all over the board. I had no pressure signs or anything. At that point I really didn't want to shoot the next, but it got way better.

Part of your deviation is in the machine itself. With only a 12-inch spacing between screens, and a + or - of .0X" in reading error, coupled with a clock of 1MM CPS, you might have two shots of exactly the same velocity which register 10 or 15 FPS different. The little Chrony is an excellent machine for the money, but it is simply not built to yield the accuracy you impute to it.

The bottom line is that the Chrony is very good (if you can tolerate the frustration of occasional non-registering shots) for providing you a reasonably accurate average velocity of your loads, plus an idea of how consistent they are. Don't sweat indicated velocity variations of less than 50-75 FPS.

And you've gotten good advice not to rely on samples as little as three shots to determine either velocity consistency or grouping. There is nothing at all wrong with using three shot groups to evaluate a hunting rifle (in fact, they will tell you more than a ten shot group since barrel heat will undoubtedly impact grouping in most hunting rifles). Three or so three-shot groups, each starting with a cool barrel, will give you a good handle on the accuracy of a hunting load.

Hoping not to confuse the issue but I only bring out the chronograph after I have an accurate load.
Then it is only to check velocity so I can calculate ballistics and make sure it is giving me the velocity I set out to get.
And 100ft difference in velocity is only going to make about a 1 inch difference at 350 yards. Not relevant unless you are shooting squirrels.
As stated by others, 3 shots is not a statistically valid sample. 5 would give you a general idea, 10 is getting there and 20-30 would be better but who cares as long as your load is accurate and you have a good idea what the velocity is.

I'm not sure what type of chronograph you are using, but re-read the above post. Even with an Oehler 35P there is some variability inherent in any measurement.

Shoot lots of rounds, 5 minimum and 10 is much better to get meaningful data. A standard Deviation under 10 is exceptional, and typically anything in the teens is very good. This will equate to at least 50fps spread in a shot string, and 100 fps in a string of 20 shots is not uncommon.
Don't get chasing the wrong data. By definition the spread will increase the more rounds you shoot. A quality load will still generate a small SD, as it essentially discounts the occasional flyer.
Use the data to compare load to load. One load that produces sd-20 is not twice as good as another load with an sd-40, but is an overall indication of load consistency.
Collect all your data, keep it organized and filed over the years, and you will learn a lot about the real mysteries of reloading and shooting. All data sets contains anomalous points if you look hard enough.
Bill

Just some comparisons of ammo:

M262 (BHA w/77 smk) sd 18.42 es 43 avg vel 2833
XTC (WCC 06 brass) sd 12.55 es 32 avg vel 2704
XTC (WCC 07 brass) sd 16.50 es 52 avg vel 2705

I load my match ammo for a Rock River NMA2. M262 from Black Hills is issued ammo for the Navy matches. I am happy with groups at 2700 fps and 77 SMKs, about 1 inch at 100 yards prone groups, so I didn't hot rod the rounds up to 2800. At 600 yards 50 fps is 5 inches for this load.