I just bought a beta master chronyand it seems to work fine. My question is how accurate are they? Are they dead nuts on or say plus or minus 10 feet a second? And what should a guy expect on velocity devation?

HP,.
welcome to the forums.

these are rated at 99.95% from the manf, same as the oehler.

as you don't have 3 or 101243910 to "normalize" it, shoot some match quality 22 LR over it and see.

just record what you record and call it "good"

jeffe

I weigh each powder charge, have trimed all cases, necked sized only using Norma brass and Berger bullets my average devation was 28 fps, is that normal or are my loading skills crappy

How many shots were in your string and what was your extreme spread?

The internal "clock" in the Chrony is crystal controlled. Even a cheap crystal drifts no more than about 10 PPM per degree C, so that's not going to be your source of error.

The distance between the sensors is fixed, assuming you open the box all the way.

Since speed is distance/time, you will know speed as accurately as you know the distance between the sensors, and the transit time.

The one fly in the ointment is that the stop and start trigger pulses generated by the sensors are not a clean square wave. If you use the extension rods, it will broaden the pulses, and knock about 25 fps off your speed. If your screens are in place, and the sun starts to go behind a cloud, the same thing will happen. A good rule is to chronograph only when the sulight is direct enough that you can see the shadow of the tripod and Chrony.

denton,
that kinda splains why i had trouble with mine today... 1/2 of the shots, first time ever, but it was a yucky, cloudy, light, cloud moving quick day

you mean the remote reads 25 ft too slow?
HFS


jeffe

I shot a 5 shot string 22-250
3522
3470
3548
3487
3476

Average devation is 28fps

I had an old boy at the range tell me he can get a devation of only 5 fps. Now either my reloading skills are sucky (which could be) or he is full of crap, there is a heck of a lot of difference between 5 and 28, does this sound right and what can I do to cut down on my devation or is 28fps worth worrying about?

quote:

I had an old boy at the range tell me he can get a devation of only 5 fps. Now either my reloading skills are sucky (which could be) or he is full of crap, there is a heck of a lot of difference between 5 and 28, does this sound right and what can I do to cut down on my devation or is 28fps worth worrying about?

Twenty-eight FPS with a .22-250 isn't bad, for two reasons:

First, the Chrony has a short screen spacing and the detectors are not quite as consitent as, perhaps, Oehler. As a result, you will get a little more variation with the Chrony than with an Oehler. That's not to say that the Chrony is a P.O.S., quite to the contrary, it's a serviceable and economical machine; but it won't give you the precision that some machines are capable of.

The second reason is that a .22-250 is usually loaded at densities that are less than case capacity; this is due to the weight of the bullet and relative speed of the powders normally used. Standard deviation tends to be higher with lower density loadings and lower with slow powder, heavy bullet, high density loadings. I can't tell you exactly why this is, but I know it to be true from 30 years of fiddling with rifles and chronographs.

Bottom line: Your loads might be actually running an SD of more like 20 FPS. Twenty FPS is excellent in a .22-250 (expect double that in factory .22-250 loads). As far as your "acquaintance" bragging about 5 FPS SD, well, that's like a 250 yard shot at a prairie dog turning into 400 yards over the barbarque pit holding the third beer. I've seen SD's close to 5 FPS occassionally, but it has more to do with the luck of the draw than with loading techniques; and such low SD's have always come with only a few rather slow powders, high loading densities, and generally larger calibers.

By the way, I've never seen any detectable increase in accuracy between a 20 SD and a 10 SD.

My pact model 1 gives me ES, SD,(standard deviation) and AD,(average deviation), for each string. I always see tha AD as a smaller number than the SD. I've never been able to figure out just what AD is. SD, I know, is a number that predicts how many FPS any bullet will be from average velocity in a string. In other words, say an average is 3000 fps with a SD of 10, then you could predict that another series of loads exactly like those in that test string would be whihin 10 fps of 3000 or 2990 to 3010.

Shooting one string of 5 shells, getting a SD of 10, then saying you can predict the next batch will be within 10 fps is shaky reasoning. I wouldn't make that prediction without shooting 10 5 shot strings, then getting a SD of around 10 for each string.

That said, If I see an AD of over 10 for any load, I junk that load combination for any further testing. I my experience, a AD over 10 shows the powder is NOT suited for this particular bullet, case, caliber combo. It is either to fast or sometimes too slow.

I would think that you should be getting AD's under 10 for that caliber. Take that with a grain of salt, as I don't currently have a 22-250, when I did I didn't have a chrono.

This is my two cents (it and $2.00 will buy you a cheap cup of coffee).

1. Chrono's will drive you crazy; I think the best use of them is to determine the actual velocity (vs. that listed in a reloading manual) of YOUR rifle's most accurate load. This will help you build a zero chart for distances greater than you normally shoot

2. You are working with a small string; 10 would be better; 20 even better than that;

3. You offered AD and the other post was about SD. There is a difference; make sure you are talking apples to apples.

4. Yes, you can get very low SD; but the point is to get the smallest group; things like SD, AV, AD, ES, etc. are potential indicators of group size but they are not the end all to be all;

5. I pursued this stuff last fall (stopped due to winter's arrival); My "loads" usually shot excellent groups; I was having some problems with miss judging winds (and missing rifle zeros at given ranges) after a powder lot switch; chronoed things and learned that the loads with the new powder weren't generating the velocity of the old powders; also learned that my numbers weren't great but the groups were very good (using .223); put this out on another board to learn that not all cartridges follow the rule of low numbers = great groups; ps: I also used 5 shots groups and was told too few to really know what is going on.

Hope this helps,

Gurrie

the 5 shot grop measured at 3/8 of an inch at 100 yards with the average devation of 28fps, all the post have been of great help, but I can see the chronograph will likly make my now gray hair fall out. So what would be my next step in lowering my average devation, I would guess weighting each bullet and each case and loading them in groups?


Ok one more thing I think I understand average devation, (average the 5 velocities then find each shot devation from that average, add the devations then divide by number of shots) but what is standard devation?


If this is a dumb question please say so but have patiences, hit me in the head enough times and I will get it!

Standard deviation is the best number to use for dispersion. The range, fastest minus slowest, is very, very nearly as good for five shot groups.

As stated, shooting one group, and getting an SD of 10 fps, is a poor indicator of what your next group will be. The reasons are too long to go into here, but you can read the standard deviation article at http://www.shootingsoftware.com/tech.htm. There is a great deal of foolishness propagated in the name of standard deviation.

My experience is that below an SD of 30 fps, or maybe more, there is little or no improvement in accuracy. Of course, I'm not a benchrest shooter, and I'm thrilled with half inch groups. You can make yourself crazy seeking 5 fps standard deviations, but I don't think it is going to help your results.

Hawkeye...

Standard deviation gets wrapped in a bunch of nonesense that makes it hard to understand. The basic concept is really very simple. At it's core, SD is just a dolled up measure of average dispersion. The bigger you SD, the more spread out the data.

First, 3/8 inch isn't a "bad" group. I might try moving the target out to 200 yards. If the resulting group is still under 1" I not sure you need to work too much more.

But in the event that you are on a quest for the consistent one hole group, I would play with primers before weighing brass. By this, I mean trying groups with different primer brands and types (mag. vs. standard vs. benchrest).

I have seen several barrels express definite "opinions" on what it likes in a primer.

Weighing brass can help group size. The dogma is to to create .5 grain groups and shoot these groups together. Regardless of the brass used you will find some alittle on the light side and alittle on the heavy side with most pieces falling in the exact middle. Where this curve falls on the weight scale depends on which manufacturer you use.

I would never weigh bullets unless I was using military sourced bullets (55/62 or 147's, de grainers). There wont be enough difference to matter if using a standard Sierra or Hornady. If you really think his matters, treat yourself to some Sierra Benchrest Bullets or custom benchrest bullets from a known maker.

Finally, I think better groups are more a function of developing consistent trigger control, breathe control, learning to read wind and mirage groups which requires going out and shooting and less with minding these benchrest details (given you are shooting small groups to begin with).

hope this helps

Most say SD/AD is much do about nothing. What I look for is consistancy. By that I mean if a load developement is building velocity in a steady straight line, and the SD and AD are at 15/10 respectivly, then the powder, bullet, primer and case combo is a good one. That's why you see certian powders in loading books and not others. They actually did try other powders, but found they were not at all consistant. Usually it has to do with the burn rate not agreeing with the shape of the cartridge.

Sometimes you get consistancy but not small groups. Why that is is another complete argument intirely. Barrel vibration, defective crowns, excess fouling, loose scope mounts, I could go on for a 100 more reasons why you're not getting good,(read small), groups with an otherwise consistant load. Sometimes it's as simple as backing away from the target another 100 yds, to find the bullet has gone to sleep and is actually quite accurate.

Or you could go and shoot BP - rounds like a 45-70 loaded with BP and heavy bullets can produce ES of less than 10 fps with best loads - but nitro loads usuallly produce much more. Bottom line, if your shooting is good, stop worrying about the numbers and keep shooting... the aim is good groups, not good Chrono figures.

Thanks guys, I think I will take the advice and tinker with primers, seating depth,and my shooting ability and see if I can`t shrink the 3/8" group,,,and streatch out to 200 yards

quote:

Originally posted by Hawkeye Pierce:
the 5 shot grop measured at 3/8 of an inch at 100 yards ...

Hey Hawkeye, My recommendation is to leave the chronograph at home.

Apparently you used the chronograph to help develop the Load and if the Load is SAFE in your rifle, then good for you. Now go adjust the Seating Depth and see if you can tighten things a bit. But, it will be very difficult to improve on 3/8". I'd suspect only "Trigger Time" will help.

It seems a lot of folks focus on everything except the group when trying to get the best accuracy. They have a standard list of arguments that go to the tune of, if the SD isn't low then there is no way to get good accuracy. In some situations that is true and in some cases it just isn't.

Focus on the groups and forget about SD, BC, chronographs and all the other stuff. Develop your Loads using the, never improved upon, Creighton Audette Method and then fine tune the Harmonic with seating depth changes. Once that is all done, if you are still interested in the Velocity and SD, try the chronograph then.

The only way to get an accurate load is to focus on the "group".

[QUOTE]Originally posted by Hawkeye Pierce:
I had an old boy at the range tell me he can get a devation of only 5 fps.

Can this old coote get a 3/8 group?
For my humble shooting, thinking laterally,
once i get a good load, and 3/8 would be it,
I use less shots per group. Two is good, last
two were 7/16, cuts down on wind errors etc
yet still proves the "zero".
JL.