As JoKa said, it is a measure of the variability of your ammo. Lower numbers are better. My not very expensive and old chronograph automatically calculates the average, extreme spread, and standard deviation (SD) for me. Are you sure yours doesn't? I have always assumed they all do.
Velocity spread... Is this acceptable?
- Thread starter Evil_Dark
- Start date
As JoKa said, it is a measure of the variability of your ammo. Lower numbers are better. My not very expensive and old chronograph automatically calculates the average, extreme spread, and standard deviation (SD) for me. Are you sure yours doesn't? I have always assumed they all do.
- Location
- Prince Albert, Sk
I have the Caldwell chronograph with the IPhone app., and it looks like it is able to calculate all of these math automatically. I will go test it right away 
!
Does the neck tension is the major thing that causes fluctuations on fps (supposing that the powder charges are constant)? What are the main factors that plays the most with velocity (for the same powder temperature and environment variables)?
Dark
!Does the neck tension is the major thing that causes fluctuations on fps (supposing that the powder charges are constant)? What are the main factors that plays the most with velocity (for the same powder temperature and environment variables)?
Dark
"as a relatively beginner shooter" you'll find most tweaking won't matter till you can consistently shoot 1/2 MOA which 10TR should be capable of.
Tweaking is fun but spending hours to produce <1/2 MOA rounds for a 3/4 MOA shooter is not very productive.
Best to shoot lots (thousands of rounds) till you are confident with 2 shoot ladder groupings.
Tweaking is fun but spending hours to produce <1/2 MOA rounds for a 3/4 MOA shooter is not very productive.
Best to shoot lots (thousands of rounds) till you are confident with 2 shoot ladder groupings.
hometownhero
CGN Ultra frequent flyer
- Location
- Toon Town, Sk
That could be the problem right there. Get a bullet comparator kit and measure accurately (hornady makes one). Measure 20 bullets from base to tip and you will see they are very different.
Ok so what my afternoon session gave me as results:
Hornady Match BTHP 168gr, IMR 4895 40.4gr
15.5 Celcius, 29% humidity
2574
2605
2580
2591
2580
2607
2626
2600
2599
2581
2544
2562
So this gives the SD at 22.05, ES 82fps, average of 2587fps
Groups were 4" at 300 yards and 5.5" at 500 yards. I a bit happy with the 500 yard group, but still need a lot more improvement!
The wind was tricky, pushing between 0 and 15KPH, in bursts so hard to predict for a beginner like me with the wind. Anyway, the wind did'nt change the velocity...
Conclusion, I will continue the load developpment to try finding a better load It will turn around the 40.4gr so i'll try change by 0.2gr increments, looking more with consistent velocity and groups at 300 yards. I will try to extend the COAL (actually 2.793") to see if it helps.
Dark
Hornady Match BTHP 168gr, IMR 4895 40.4gr
15.5 Celcius, 29% humidity
2574
2605
2580
2591
2580
2607
2626
2600
2599
2581
2544
2562
So this gives the SD at 22.05, ES 82fps, average of 2587fps
Groups were 4" at 300 yards and 5.5" at 500 yards. I a bit happy with the 500 yard group, but still need a lot more improvement!
The wind was tricky, pushing between 0 and 15KPH, in bursts so hard to predict for a beginner like me with the wind. Anyway, the wind did'nt change the velocity...
Conclusion, I will continue the load developpment to try finding a better load It will turn around the 40.4gr so i'll try change by 0.2gr increments, looking more with consistent velocity and groups at 300 yards. I will try to extend the COAL (actually 2.793") to see if it helps.
Dark
hometownhero
CGN Ultra frequent flyer
- Location
- Toon Town, Sk
No it means what what you are measuring is not consistent. One round might be 5 thousandths different length from tip to the bottom of the brass. But if you were to measure the ogive it would be the same length. So you would be adjusting the seating die trying to get them all the same but what is happening is how far the ogive is from the lands would be different.
Curious question, how did you get to the 40.4 gr load? How did you work-up your load?
Usually when I'm doing 10 round strings, its when I'm going in 0.1gr increments, or actually testing final the load.
Yeah, well, First I developped the load with 0.5gr incréments, which ended with the best one at 40.0gr of IMR-4895. It was with my Lee scale. I bought a new RCBS 10-10 scale, so I compared the 40.0gr on the RCBS and it ended to be 40.4gr with it, so I sticked to 40.4gr measured with the RCBS. I don't know which of the two scale is offset, but the RCBS is more precise, it reacts more to every single granule that falls off the trickler.
Dark
That's awesome.
I always joke around that if I ever purchase some land it will be 2km long and only 100ft wide
What I was actually driving towards was a point that "Burnaby" made. (Based on your first post)
It might be worth shooting some groups with an establish long range shooter. Then you can see if it is the ammo or the shooter and which on you need to work on
If you close to Calgary there are lots of people here that we can introduce you to. If not, well, I am sure someone else here would also be happy to throw there hands up for another shooter.
I always joke around that if I ever purchase some land it will be 2km long and only 100ft wide
What I was actually driving towards was a point that "Burnaby" made. (Based on your first post)
It might be worth shooting some groups with an establish long range shooter. Then you can see if it is the ammo or the shooter and which on you need to work on
If you close to Calgary there are lots of people here that we can introduce you to. If not, well, I am sure someone else here would also be happy to throw there hands up for another shooter.
