Velocity Spreads

[NCswamp]

I am trying to isolate the reason I am seeing high velocity spreads with my 28 Nosler loads. I recently shot a OAL length ladder - 15 rounds in groups of three. My velocities were all over the place in some case as much as 100fps!! I even shot a group of factory ammo and it had a spread of almost 30fps. In several instances I had single digit spreads for two rounds then a round 100 fps higher or lower. i also had four errors from the chronograph which seems high.


I believe that one of the following three things occurred: human error, variance in new brass, or bad chrono measurement

I acknowledge that sloppy work or human error is possible but I've never seen numbers like this. I individually trim each brass to .002, weigh each charge to 0.1 gr, and measure each bullet and brass / cartridge. I have not routinely weighed brass or bullets. I was using new Nosler brass (never been fired), 168 gr ABLR bullets with US 869 powder, and no crimping. We had wind blowing 4 to 8 at 6:00 and I did notice the chronograph bouncing slightly.

I would appreciate some help...thanks

 

[TXbaldhunter]

I have found that the angle of sunlight can really play games with a chronograph.I saw the same thing one morning at the range.The range was setup shooting to the East.My velocities were around a 100fps difference from 7:00am to 9:00am.I was always getting different readings just about everytime I'd go to the range.I have since move to another location at the range where I am shooting to the North.Now my velocities are running real consistent and I'm getting nearly the exact velocities whether I'm using my Pro Chrono in the sun or my Magneto Speed from under the covered shaded shooting bench.I guess if you think about it,if the distance from where the first eye sees the bullet to where the second eye sees it is altered by anything like a shadow it can throw off the chronographs calibration for reading the velocity accurately.That was one reason I bought a Magneto Speed.The problem with a Magneto Speed it can alter your point of impact because it attaches to the barrel.I guess the Labradar is the best,but costly.I like a regular chronograph when I'm testing loads for accuracy and velocity.A Magneto Speed is great for just testing velocity and you can work with it from the bench.