Chronograph set ups, let me see them!

[theunrulychef]

So I thought I'd take advantage of the rising temps to get out & test a load in my new 260 bolt rifle. I put up 10 level targets, got my Chrony all set up about 15' away from the bench & fired 50 shots in a round robin style to try & find the optimal charge weight. While I seem to have found a couple good nodes that I will explore further, the chronograph data made no sense. Some of the best groups had horrible SD & some of the worst groups had the best SD. Trying to make sense of it, I did a google search for chronograph accuracy & I find out that everyone says not to shoot on the snow because of the reflections. Doh!

Anyways, I guess my next project will be to build a box for the damn Chrony, possibly with some LED lighting inside & flat black paint to reduce any shadows. Does anyone have a cool chronograph set up they'd like to show for ideas? I've seen some online that look like huge wooden boxes, but I'm thinking "portable" as a main goal here.

[Brick]

I've never heard of reflected light from snow being a problem. And I cannot even begin to think of why it should be. The only tweak I've found is on cloudy days, do not use the sky screens. And some Chronos will not react to indoor light.

[wanneroo]

Well I guess I am going to find out tomorrow when I do some new load testing. My ranges are still buried under snow and as it is I can only use one of the short range ones.

[theunrulychef]

My understanding is that they work on the contrast between the bullet & the diffuser shields or sky. When the snow is out & there's so much light bouncing up at the bullet, it's harder for it to differentiate. I was also by some trees (though I didn't think I was in their shadows) & the sun was out pretty bright yesterday. I only had one ERROR code come up, but I just felt like my readings weren't matching up with what I was seeing.

Maybe I just need a new battery, haha.

[usmc21]

I know in very sunny days my chrono will have difficulty reading properly even with the sun diffusers on. the instructions also said to take a sharpie and blacken the bullet to help pick up the bullet better.

[wanneroo]

I ran my Chrono yesterday in a snow covered area. By the time I got out there overcast skies set in, but everything functioned normally with no problems.

[BobGun]

So I thought I'd take advantage of the rising temps to get out & test a load in my new 260 bolt rifle. I put up 10 level targets, got my Chrony all set up about 15' away from the bench & fired 50 shots in a round robin style to try & find the optimal charge weight. While I seem to have found a couple good nodes that I will explore further, the chronograph data made no sense. Some of the best groups had horrible SD & some of the worst groups had the best SD. Trying to make sense of it, I did a google search for chronograph accuracy & I find out that everyone says not to shoot on the snow because of the reflections. Doh!

Anyways, I guess my next project will be to build a box for the damn Chrony, possibly with some LED lighting inside & flat black paint to reduce any shadows. Does anyone have a cool chronograph set up they'd like to show for ideas? I've seen some online that look like huge wooden boxes, but I'm thinking "portable" as a main goal here.

I have noted this problem often. If you are shooting 5 shot groups SD really is not a good measure of consistency. SD of a 5 shot group is often gives strange results because the sample is not large enough. I take any group that shows promise by size and then shoot 20 to check the SD and in most cases if the SD is good the group sizes reflect that. Also SD is more important as range increases at 100 yards the difference in velocity does not make that much of a difference until it gets really large.

The other thing that enters into group size is shooter ability and shooting platform stability.

[PAwhitetailbowhunter]

As far as snow goes, I have read that it can be an issue as has been mentioned, but I was out twice so far this year with my Caldwell Chronograph that links to my iPhone shooting over snow and it worked very well. I am thinking it functioned fine and snow was NOT a factor as I was testing sub-sonic 300 Blackout loads and was just on the border of SUB/SUPER sonic and the ones that did NOT crack were around the 1050 FPS and the ones that did crack were closer to 1100 FPS.

To address the question raised by the OP. I have no idea why the larger spread could at times make a better group? BUt Think what is the goal? What do you plan to do with the data? If the only goal is more accuracy at 100 yards then work up differnt loads and shoot for groups. If you are going to use the data to figure bullet drop out to 600/1000 yards then maybe you want that tighter velocity spread. I am new to Chrono use and am mainly using it for Sub Sonic loads so I am making sure I get Sub sonic and then within the Sub Sonic arena I will fiddle to tighten groups.

In terms of portability, maybe some sort of Black cloth streatch over a light weight frame that would sourround your Chrono?

[theunrulychef]

The goal for this rifle will be longer ranges, which is why I'm paying more attention to the velocities. If it was to punch paper at 100 yards, I've got a couple 1/2" groups there to tweak, but the velocity spreads on them were kinda crazy. One was 113 & the other is 160. No consistency at all.

I'll build up a small light box with LEDs for the top & have it sealed on the sides. I'm sure it could use a fresh battery as well. Then I'll run some 22lr through it to make sure I'm getting some consistent numbers before running a load test again.

[Zeeba]

Don't forget Rule Number One:
Don't shoot the Chronograph