Does this sound like chronograph trouble?

[Guest]

I did some load testing this morning.I was only interested in chronograph results.I took a handful of brass that came from the same lot and has been neck turned, but all pieces are in different stages of use.Some are a lot more used than others.
My procedure was to take one piece of brass, load it, shoot it,write down the number,then get another piece of brass and repeat with the next higher charge. I ran out of time before I hit pressure.At 54.7gr my chrono started giving me error readings. I tried about 4 shots all with the same charge,all with errors.So I moved the chrono back about 10ft into the sunlght and had no more errors.
I was shooting at 130yds.
Now here is another strange part, this coupled with the chrono readings.My first 2 shots were away from the main group by about 1 inch, and well dispersed.All the rest of the shots formed the main group which measured less than .75 inch. And the wind was pretty bad.
Now here are the strange readings.
52.7gr 2939fps
53 2997
53.3 3028
53.7 3017
54 2937
54.3 2985
54.7 2915
55 2928

Powder is h4350, weird huh?. .264 win mag,140 a-max,27in kreiger.

 

[4mesh063]

That doesn't seem all that surprising to me. Had you used cases that were alike, and had just finished shooting them for ES and they shot under 25 or 30, then I'd be willing to beleive that there is a problem. But, with just a bunch of scrap brass, I'd be inclined to say that there could be that much ES (100fps or so) depending on a million other things. Also, the length of the barrel, while probably long enough to burn that 4350, may not get all of it burnt and if it doesn't, you may get a bunch of ES, casusing more powder to actually shoot slower.

Your cases have a lot to do with the efficiency as well.

Go buy some new brass and start testing with that. Keep a set of test cases together so the results mean something to you. Allways fire ALL of them so they are fired the same number of times.

Also, try different primers. Get away from magnum primers in that thing. You also have 20 some grains of powder capacity left and I dont really know, but, people say that's a bad thing. I've never seen it to be, but I never really looked for it either.

 

[Brent]

I would check the Chrony against an Oehler 35. I don't trust any data from a Chrony for this type of work yopu're trying to do.
After going round and round with two of them and getting up to 200 fps fluctuating readings... from both of them, I upgraded to the 35 and I got something that WORKS now, all the time too. Cept in fog or dark that is...

Like Phil said, start with new brass and keep them together and fired the same number of times, I number mine and keep track of every firing on each piece.

I think your erratic variations are coming more from the chrony than the brass tho, IMHO.

Did you start with a clean barrel there?

 

[Austin]

I have both a Chrony and an Oehler and they are running a consisitent average of about 15fps spread. I guess I got one of the GOOD Chrony's! HAHA! Anyhow, as stated above, it doesn't seem at all unusual considering your brass. Take the brass, weight it dry, then fill it with water and weigh again. I'm pretty sure you will see some inconsitencies. Velocity and pressure can change with as little as 2.2x10^-2cc difference in combustion space so it's pretty likely your brass is causing such erratic behaviour. Whereas, Oehler IS somewhat a better quality product than the Shooting Chrony, the Chrony can at least be said to be consistent within it's margin of error. There again, I have had four of five of my Oehlers turn out to be total junk. When I develop a new load, I use three different chronos and take an average. Another method I use when determining case capacity is to use a syringe to measure water into the case a little at a time. This gives a more consistent and accurate reading since you can use the Mass x Volume = Density equation, rearrange to solve for your unknown, and determine an EXACT capacity for any given case. I have found the latter method to be the absolute most accurate out of all methods and I, personally, swear by it. Good luck bro!

TH

 

[Brent]

Austin,
Your freakish bad luck with the Oehlers and GOOD luck with the Chrony is the norm you think?

I've used the two Oehlers I have for a long time now, and there's no comparison between them and the Chronies. I get the same speed day after day with both of them, this I like!

What problems did you have with those Oehlers?

 

[Austin]

I have always been an Oehler freak, so I would say that it is anything BUT the norm! For some reason, the ones I got (all purchased within 4 months of each other) would give inconsistent readings. These are the only Oehler's I have EVER had problems with. I have a Shooting Chrony that has been very good to me for some reason. As you said, it seems a little freakish for an Oehler (and more than one at that!) to have such problems. I haven't ever used those again and I have stuck to my one good chrony that I have tested against numerous other Oehlers and it has been the most consistent Chrony (out of 14) that I have owned as of yet. I'm guessing I got a few out of a bad batch or something. I have yet to figger it out or even to send them back to Oehler for repair. Haven't really been doing a lot of match shooting in the past year or so, so it has been pretty much a non issue since the deer don't seem to mind how fast the bullet is going!

Now.... You have got me wanting to find out what the heck is going with these things again so... off to get some boxes to send these little buggers back! Take care!

TH