Opinions On These Chrono Numbers?

[vh20]

I chrono'ed this load yesterday and got the results below. It shoots into a bughole at 100, shoots sub-1/2 MOA at 500 typically, but I've been having some trouble at 1000 (unpredictable results, and sometimes all over the place, but I'm not sure if there may be a scope problem, etc. causing that). Last week shot a sub-4.in. group at 1000 with it, and a 1.75 in. group at 500. Load is for .338LM: Lapua brass, Win. WLRM primer, 89.9 gr. Retumbo, 300 gr. SMK touching lands.

Over 10 rounds, I got the following numbers (Pro Chrono Digital):

1) 2715
2) 2704
3) 2704
4) 2726
5) 2743*
6) 2721
7) 2710
8) 2726
9) 2715
10) 2726

AVG: 2719
ES: 39
SD: 11

That ES is disappointing. HOWEVER, Shot #5 seems to be an anomaly in that string for some reason, and nearly doubles the ES all by itself. It doesn't seem to fit (possibly an error?) If I omit it from the string and consider only the other nine, the results look like this:

AVG: 2716
ES: 22
SD: 9

Would you call it good? It seems like I've been tuning this load forever, but this one seems to be about the best I can do.
Thanks.

 

[jkonzal]

It's been my experience that the 300gr SMK likes some jump. I have found .030 - .050 to be the window that works for me. How many reloads on your brass? Have you annealed your brass?

 

[vh20]

Their on their 5th firing, annealed after the 3rd. I got best groups at 0.000 jump, but don't know about ES/SD at other lengths. What kind of ES/SD are you seeing?
Thanks

 

[jkonzal]

I use a magneto speed chrono, set for SD. Here is what I got:
Max: 2965
Min: 2939
Avg: 2951
SD: 9

 

[milo 2.0]

If it shoots that good, I'd run with that load. Neck tension can skew numbers through a chrono more than anything. Try grabbing 10 off your press that feel identical when you seat bullets, then run them through the chrono, see if things tighten up.

Read this thread from 6mmBR;

New 21st Century Shooting Hydraulic Arbor Press

 

[Rprecision]

Several times I have seen spread on a chronograph that made me pissed before I ever left to look at the target. Then I found my target with only one ragged hole.

So I have concluded the my spread is either (1) not as important as I thought or was led to think (2) its so great it the "bad" bullets never hit paper

either way, I think chronographs suffer two problems, they are not as accurate as we think, they are not a perfect tool for measuring precision.

I use the chronograph to get a idea what's what and let the target tell me what it likes. The last three loads I worked up in three different rifles all had a accurate load which the chronograph disagreed with. I don't have a explanation for this but have talked with a number of folks that had similar results.

And to put it another way the maximum deviation you have is .014 or 1.4%

 

[vh20]

Thanks for the replies. I'm happy with 90% of that string. It's Shot#5 that caused me to post the question. Without it I'd be sold on this load without a second thought. Your thoughts have been helpful. With them in mind, I think I'll probably just stick with this load and call it good for now. Thanks for the advice.