Chronograph Info

F

fx77

Member
What kind of extreme spreads and sd are acceptable for a group of loads that the competetive benchrest shooter finds acceptable?
 
Nobody I know tunes with a chronograph. A chronograph is just a tool to tell you approximate velocity. I could care less about extreme spread it's how the gun looks on the paper that counts.
 
its all about the holes on the paper in short(100/200/300) benchrest.

mike in co
 
I thought that consistency in loading would asist one in obtaining smaller groups. The SD and ES would help determine the uniformity of the
cartridge's performance. this purely as a measurement tool. Am I wrong?

If all the speeds are unequal to begin with and have high ES and SD's would they not give inconsistent results provided all other items in the loading process are constant?
 
I think most have found

fx77 said:
I thought that consistency in loading would asist one in obtaining smaller groups. The SD and ES would help determine the uniformity of the
cartridge's performance. this purely as a measurement tool. Am I wrong?

If all the speeds are unequal to begin with and have high ES and SD's would they not give inconsistent results provided all other items in the loading process are constant?
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at the shorter ranges, the numbers don't mean much. One can find pretty, small holes with loads that exhibit larger es's sometimes. We mostly deal with speed nodes, if you will, that are known to provide good accuracy. You can wear out a great barrel trying to find small es's ;).
 
A chronograph can tell you MUCH more than just a basic velocity reading IF you know how to read the data. If you don't, you cuss it and make excuses. If you do know how to read it, you use it often.:)

Yes, they are more important for longer distance shooting but they have their place in short range too. The paper is of course what matters, but every tool you can utilize to damage as little of the paper as possible will help.;)
 
In short range 100 to 300 yard BR, any extreme spread is acceptable as long as the groups are acceptable.
Ted
 
What others have said is basically true--what does the group look like regardless of numbers--but given two loads that "appear to be equal", I will take the one with the better numbers (if they are substantially different) because I believe it will show in vertical at the longer 200-300 yardages and over the long haul. To answer your original question, many of the groups I have measured are in the single digits for Standard Deviation (SD) and Mean Average Deviation (MAD). To get those numbers to be single digits, the ES will be in the low to high teens or less. Be careful about drawing conclusions on a few groups. These numbers don't mean a thing until you are able to repeat them over 10-20 groups or more over several days. Basing decisions on a few groups is hap-hazzard at best--no different than basing your load on just a few groups. It must be repeatable. Randy J.
 
I'd be willing to wager that I've sent more bullets over a chronograph in every condition imagineable than 99.9% of the people on this site and I can tell you one thing I've learned...........loads with low standard deviations are more forgiving of temperature swings than loads that have high deviations. Yes, a high SD load might punch a teen group. Once. Maybe twice. Maybe even several times. But throughout the day, and especially in big temp swings, the low sd load will give better results.

In other words, a load that shoots a group in the .100 inch range with an sd of 20 fps would eventually be overcome by a load that shoots .150 to .200" with an SD of 5 fps.

This is probably the root cause of why guys get to scrambling to find a new load a few matches into the days first agg. They had a load with a high sd that shot great at one particular atmospheric condition but once that condition went away, the inconsistencies in the ignition and combustion of their load opened up their group size.

In my testing of 6ppc's in major temperature swings, I have seen and recorded this phenomenon dozens of times. In my most recent test of charting and mapping out loads with N133 vs. H322 in 50 degree temp swings, I noted that H322 would give smaller groups "on occasion" than I could attain with N133 but that N133 was much more forgiving of temp change and SD's were smaller throughout the load ladder therefore making it easier to keep the gun in tune. When temps got into the 90's, H322 had node windows only .3 of a grain wide and N133 actually enlarged it's windows! So for someone concerned with staying atop the "tune" and trying to hold together four aggs across the span of two days, N133 would have been the clear winner. I could have chosen H322 and gone for a small group trophy, or I could choose N133 and go for the agg trophies.

Obviously, if you never set up a chrono, you would never know any of this. You just "paper tune" and sometimes you luck out and sometimes you don't. But whether you luck out or whether you don't, you wouldn't have known why.;)
 
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I'd be willing to bet that less than 1% of the shooters that place in the top 50% at a shoot tunes over a chrono. I know super shoot winners, world shoot competitors and shooters that win on a very regular basis that don't even own one.
 
fx77,
I will not cast stones on the guy, but I don't remember seeing his name on a winners list. I use my Ohler35P occaisionally, but lack of practice is my Bugaboo.
Most successful BR shooters keep copious records and know which load will work with different conditions for a particular barrel.
Butch
 
Here's the deal. While everything that has been written here is true, some top shooters, are now weighing every charge. I think that this eventually gets around to consistency in velocity. Also, there is the matter of the inherent bredth of tune that a particular node for a particular barrel/rifle will exhibit. The narrower the node, the more likely that excursions from the average velocity will fall out of the "still in tune" range. None of this matters if you miss a condition change.
 
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A "friend" shot my Oehler and failed to replace it. I tried to buy a new one. Ken Oehler would not sell me one. I bought a new Chrony beta master. It seemed to work just as well as my old model 35. I still have it.................somewhere. I'm pretty sure........
 
Here's a good way to settle the issue of the true value of SDs and ESs. Ask Tony Boyer if he uses them in his shooting repertoire and how much value he places on them. In all my readings, so far, I can't recall him ever mentioning the subject. Maybe I just haven't read enough OR he placing value elsewhere.
 
abintx said:
Here's a good way to settle the issue of the true value of SDs and ESs. Ask Tony Boyer if he uses them in his shooting repertoire and how much value he places on them. In all my readings, so far, I can't recall him ever mentioning the subject. Maybe I just haven't read enough OR he placing value elsewhere.
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Good point but I don't think you could say that Tony has never shot over a chrono. If he doesn't use one now it's because he probably has learned what to do and when simply by experimentation. I guess that's the advantage of shooting several million bullets in your lifetime!
 
Another little item to keep in mind about chronographs. They are a measureing instrument with a degree of error. Lets say that error factor is plus or minus .5%. Thats 1/2 of 1 percent, which I doubt any of them could hold. At a velocity of 3300 fps that is a spread of 33 fps. Could be plus 16.5 pfs or minus 16.5 fps. Trying to load to velocities beond the error potential of the chronograph is just silly. Yes I own one but seldom use it. I might drag it out if I am changing to a powder that I am not familar with just to see what loads are needed to get in the range where I know my barrels shoot their best but that is all.

Donald
 
The use of a chrony grows smaller over time. You just got to know when to hold them and when to play them. Most everybody I know and myself included can't even remember the last time they drug theirs outside. I think we have them just to be able to say, yeah, I got one. I'm thinking about selling it, you want to buy? They always start out as a great idea, for some reason, they sure loose that status fast. :)
 
After reading through this

a few questions: With all the loads folks have done over the years, particularly with n-133, there should be formulas so common that there could be a book published or even flip charts. I have watched a number of folks who chase their tune all day muttering to themselves and switching from one box to another without what seemed to be any clear path they were treading, It woud seem to me that someone would have written all this down by now and could garner a princesly sum for the flip chart.

Another situation is all the groups one would need to shoot to be able to prove the laods that have been discussed. Considering that some of the better shooters think that a barrel is toast after 600 shots or so, one might never be able to find out, for sure, if their data is sound. If each barrel would require this kind of testing, we would sacrifice most of the good life in a barrel to prove the loads work.

How many years have folks been using N-133?

Another situation that I think most people overlook is bullet uniformity; not necessarily runout or weight but seating depth uniformity. If one is using seating depth to establish accuracy, there is 0 margin of error for OAL's. I am hoping I have found a way around this without having to measure all the bullets I use , other wise, every bullet must be measured unless a person jams real hard. If a rifle is not shooting a paticular bullet lot it is probably because the bullets are not uniform in length where they need to be. They will all shoot prety well, including Matchkings if they are sorted properly.

I am particularly gratifird about more and more folks weighing their charges after all the years I have been flamed for advocation it, I must say. :) Perhaps more folks aughta look at their bullets now ;) .
 
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