Home Forums Hunting & Shooting Ask The Gunwriters Very strange morning shooting, re: Loads, chrono velocities. Opinions please.

Five, or three?

Why censor the high and low?

All sorts of stuff is inferred by shooters using short light-screen chronographs in varying temperature conditions, shooting too-small samples.

Why would your intent & purposes be so intensive? Shooting is supposed to be fun.

"Five, or three?
Take a completed spc chart using 5 data point averages and go back over it just looking at the first three readings and do a median chart right over the original (maybe in a different color). Look at the two plotted together and see if the 3 point median chart doesn't tell basically the same story. It is also easier for the operator to use (no add and divide).
It worked great in mfg. but probably not worth much elsewhere.
And I it is all pretty much electronically captured now.

"Why censor the high and low?"
Mostly just looking for flyers, and see above comments.

I really would like to see a repeat of the shooting session and see how that data looks.
Just my 2 cents.
Tim

But it's fun to worry over until guys like you come along. Apparently the relationship between charge and velocity holds even with H4831 or you would've found it with your experience and lab contacts. Sometimes that's why we bring it up. (A somewhat cryptic thanks.)

Has happened a few times to me too. Shot an itty bitty group then loaded 20 rounds and never duplicated said group. Sometimes not even close.

I think the saying goes, "large groups WILL repeat; small groups MAY repeat."

I use this when starting with something new. I don't load up a bunch of every variation. I load 3-5 and look for trends at the start. If I get a small variation with a few shots, it doesn't tell me much. If I get a large variation with a few shots, it tells me enough.

I don't bother with the small variation in charge weight that the OP did when trying to make some real data. With cartridges the capacity of the OP's, the smallest charge variation I bother with is 1 grain, and sometimes opt for 1.5-2 grains. For small cartridges, like 223 and smaller, I generally use 1/2 grain variation, and never any smaller than that. Even with small pistol cases like 9mm, I've only used .3 grain variation a few times; generally, I either load whatever charge seems appropriate based on the target velocity, or step in half-grains if I have no idea what the results will be with a set of components.

I concur that the combination of the limited chronograph, the tiny variation in powder change, and the small sample size explains the non-linear results.

+1

Bob

www.bigbores.ca

If you want readings that are more reliable and more often repeatable, I recommend an Oehler 35P and set the screens further apart with a longer screen rod on 2 tripods.

10 shot averages over that set up is as good as is reasonable from the hobbiest aspect.
John

Exactly.

Most of the chronographs used by handloaders have very short screen spacings. I've tested several against my Oehler 35P, and while most small, cheap chronographs provide a similar average velocity, individual shots are often quite a ways from the same shot over an Oehler.

This means when shooting only short strings, like the typical 3-5 rounds taken by most handloaders, the data is almost useless for statistical analysis. Which is why I don't have much faith (and wouldn't worry much if it was my rifle) about the limited data that started this entire thread. If you want meaningful readings from individual shots, or short strings of shots, then you have to use a more accurate chronograph.

I have yet to encounter a short "affordable" light-screen chronograph that provides that sort of accuracy. Some don't even provide repeatable results from the same load under slightly differing light conditions, and yet many shooters regard their results as indications of all sorts of stuff.

And after you've done it a few times and developed a routine, setting up an Oehler 35P isn't the ordeal some Chrony users would think.

Not even close.

I've long since stopped chasing velocities, if want more then move to the next cartridge with more powder space. What I find is case prep (uniform primer pockets,flash holes deburred and chamfered, trim cases to exact length every firing,anneal cases every firing), exact charge weights everytime, concentric cartridges. This helps get your extreme spread into the single digits, this makes your ballistic information (from a program like Bergers) much more reliable, the Quickload program will get you on a 'node' relatively quick. The charge weight can be adjusted to stay on that node when things like temperature and seating depths are changed. Precision will follow . You need a reliable chronograph for sure.

How does the CED M2 compare as far as accuracy goes?

Bob, here's a chapter from one of Bryan's books where he flushes out numerous chonographs. He thought favorable of the CED M2. His main point of emphasis (and concern) was the stability of the sky-screens.

http://appliedballisticsllc.com/Articles/ChronographChapter.pdf

Thanks 32.