Chrony Speed question

[GoneHuntingOutfitter]

I have been loading for a 7mm Rem Mag getting ready to have a long range turret built. Got a couple of loads to shoot really decent groups under under 1". Decided on one and went to the range to shoot some Data at distance. While doing this I was watching the Chrony and would get speeds differing close to 100 FPS. Ideas on what is going on? H-1000, RL 22, RL 25 powders tried. All show a big swing in speeds per Chrony. Using RCBS digital scale and trickling to exact grains. Match primers Fed Mag. 168 VLD. Is Chrony the problem, powder scale problem or other. Thoughts?
Shooting Chrony Beta Master

 

[venatic]

All the brass the same brand? All trimmed to length?
How many times have you sized and is it FL sized or neck sized and what kind of neck sizer a bushing die or regular neck die.
Has Brass been annealed?
The reason I ask these questions is neck tension is a key to consistent velocity.

 

[Greyfox]

In my experience if velocities had the kind of variation you are experiencing it was usually the chronograph, regardless of the brand. Lighting conditions, bullet reflection, and set-up, all can contribute to error. I would go there first, particularly if your readings were taken on a sunny day. I essentially eliminated this variable when I started using the Magnetospeed. I wish it was introduced 25 years ago! I would have saved a lot of time, component cost, and barrel life. IMHO.

 

[livtoohunt]

RL22 and RL25 will give up to a 100FPS spread in weather change or if in the sun, etc. H1000 has been 25FPS or less normally for me. My old Chrony was a liar so I upgraded so it may be the chrony. Lastly I have mixed brass and never had 100 FPS spread. Not saying no but never that bad for me.

 

[GoneHuntingOutfitter]

I was first shooting Fire Formed Brass with the shoulder being bumped back .003 in a Redding Die. Brass were always trimmed, Primer pockets uniformed. I thought brass were the problem and the powder RL 22 and Rl 25 possibly.

I bought new Nosler Brass and H-1000. Speed with this were 60 fps differences, I think more the powder helping than Brass.

Leaning toward a Chrony problem, but not ruling out the Brass as I have not got a second shot through New brass.

Using a RCBS powder scale digital. Always shows the correct weight with the weights they provided and gets calibrated, but now im wondering if it is sometimes off on the charge. Going to do some testing to eliminate this.

 

[RustyRick]

1016519253926101101048217085I don't know how to do it any other way. But these numbers is the spread I got today on my chrony with one bullet weight, 3 powders, and 3 shots per group. The top row is factory loads. Kinda weird eh. And there was a semi roof over the technology so no direct sun.

 

[livtoohunt]

My results with H1000 in the 300WM were all no more than 40 fps spread. This was WIN Brass, Fed215, 77grs H1000, and 200gr NAB. Most were less than 25. RL22 now on the other hand I have seen up to 100 fps swings. It is most noticeable when going from 90-degrees down to 40-degrees. My old chrony Alpha was awful!

 

[RustyRick]

1016519253926101101048217085I don't know how to do it any other way. But these numbers is the spread I got today on my chrony with one bullet weight, 3 powders, and 3 shots per group. The top row is factory loads. Kinda weird eh. And there was a semi roof over the technology so no direct sun.

That should look like this 101(factory loads), 65, 19, 25, 39, 26, 101, 10, 10, 48, 21, 70, 85

I've seen similar spreads on factory, which probably is the norm. But I'm surprised on my own loads even when I go back and calibrate, zero, and spot check loads from my RCBS 1500. Wierd