Cutting my teeth in the reloading world on my .222 rem model 700. Was wondering what is considered normal fluctuation in velocities measured through a chrony (same load recipe)? Say, in a 5 shot group how much difference in fps between the fastest and slowest should be seen normally - if the reloader is doing there job well.
Velocity Consitency - What is realistic?
- Thread starter deerfarmer
- Start date
I find that when you hit the sweet spot where your rifle groups it's best is usually also where the velocity extreme spread (ES), standard deviation and mean average deviation are at their smallest value for a shot string...The largest velocity ES I've seen was 137 fps, with the least being 6 fps...Seems like velocity consistency gels with the warmer loads.
My smallest grouping loads for various calibers have an average ES around 12-20 fps...My hunting rifles loaded hot, group well and have velocity ES in the 25-45 fps range... No experience with the Chrony and don't know of it's accuracy...I use a Pact chronograph.
My smallest grouping loads for various calibers have an average ES around 12-20 fps...My hunting rifles loaded hot, group well and have velocity ES in the 25-45 fps range... No experience with the Chrony and don't know of it's accuracy...I use a Pact chronograph.
First off, you need to understand what will cause fluctuations in the readouts from your chrony.
If you're shooting on a day with scudding cloud and interspersed with sunshine, the chrony will give you all kinds of deviating readings.
This can drive a newbie crazy pretty quickly and may give him/her the false impression there is something wrong with the loads.
Low cloud or high cloud days, rain, morning, afternoon and evening sunlight will all give different readings.
When I'm really getting serious, I use a small 12 volt ATV battery to power two bulbs over each diffuser screen. I also have a cover to protect the whole set up from errant light. This realy shows how consistent the velocities of the loads are.
What a chrony will do for you, under normal conditions is pick up on extreme velocity situations. I is especially good if you're loading to maximum or over the book loads. It takes pressure to create velocity. If you all of a sudden have a 50-100 fps increase in velocity, it might be time to reevaluate the safety of your load.
The best indication of consistency you can get is good accuracy.
The chrony is a useful tool and it will give you ball park accuracy in its readings. If you want accurate figures, you need to go to a much more expensive chronograph that uses screens or some other sort of timing principle. I saw one a few years back that a fellow in the US had made up on his own.
He was an electrical engineer and used a system similar to that used in metal detectors at varying ranges to determine velocities. It was all hooked up to his lap top. I don't know if he programmed the unit himself or not. He claimed it was accurate to a couple of meters per second.
His readings showed similar results to another older screen style unit they were using as a proven base to compare against.
What was nice about the metal detector style, was that there weren't any screens to replace and there was a 10cm x 1meter area to shoot through. The detectors were mounted upside down on plastic stands and you shot over the detector rings.
If you're shooting on a day with scudding cloud and interspersed with sunshine, the chrony will give you all kinds of deviating readings.
This can drive a newbie crazy pretty quickly and may give him/her the false impression there is something wrong with the loads.
Low cloud or high cloud days, rain, morning, afternoon and evening sunlight will all give different readings.
When I'm really getting serious, I use a small 12 volt ATV battery to power two bulbs over each diffuser screen. I also have a cover to protect the whole set up from errant light. This realy shows how consistent the velocities of the loads are.
What a chrony will do for you, under normal conditions is pick up on extreme velocity situations. I is especially good if you're loading to maximum or over the book loads. It takes pressure to create velocity. If you all of a sudden have a 50-100 fps increase in velocity, it might be time to reevaluate the safety of your load.
The best indication of consistency you can get is good accuracy.
The chrony is a useful tool and it will give you ball park accuracy in its readings. If you want accurate figures, you need to go to a much more expensive chronograph that uses screens or some other sort of timing principle. I saw one a few years back that a fellow in the US had made up on his own.
He was an electrical engineer and used a system similar to that used in metal detectors at varying ranges to determine velocities. It was all hooked up to his lap top. I don't know if he programmed the unit himself or not. He claimed it was accurate to a couple of meters per second.
His readings showed similar results to another older screen style unit they were using as a proven base to compare against.
What was nice about the metal detector style, was that there weren't any screens to replace and there was a 10cm x 1meter area to shoot through. The detectors were mounted upside down on plastic stands and you shot over the detector rings.
I have managed to even get my AR and M14 down to single digits in ES and SD. Would those results be consistent every day? Not likely, but both those rifles shoot/shot beyond belief! I only worry about velocity consistency when I'm loading for my 1000 yard target rifle. All other rifles I load for the best accuracy only. My short range bench rest rifle as you would expect can average one hole groups but do you think the velocity is what most people would call consistent? Not even close and it doesn't matter, the targets don't lie. I have a 22-250 that is superbly accurate and the velocity consistency is horrible...at time of testing. It's as bearhunter says, there are many variables that can affect chrony readings and their consistency from shot to shot. That is why I don't worry about it and load until I like what I see on paper. Use your chrony data for external ballistics calculations and to possibly help explain unexplained shots on paper. Good luck!
For me, groups under 1.5" are usually under 40fps extreme spread and under 20fps standard deviation(90% of all shots will be within 20fps). I have seen ES under 20fps and single digit SD's with a couple loads I tried. Just keep a journal and record each shot in the group, the ES, SD, and Avg then group size. This will give you a picture quite quick of where your acceptable #'s are. The #'s start to take on more meaning the further you shoot. Crappy #'s can still turn in good groups at 100. Don't forget to practice and test your loads at the ranges you'll be hunting/competing.
Good shootin'
Willy
Good shootin'
Willy
Also, don't forget that all of your run of the mill Chrony type units, are guaranteed to be within 1% correct.
1.% of 3000 is 30.
Thus, the company says being out 30 fps with a rifle shooting 3000 fps is normal. Before you start with any other variables!
1.% of 3000 is 30.
Thus, the company says being out 30 fps with a rifle shooting 3000 fps is normal. Before you start with any other variables!
My 6ppc with varget runs between 6-9 fps with select cases and turned necks
My hunting rigs run approximately 30-50 avg to support adiquate groups.
Powder/ temp/ big keys to the puzzle.
Leaving a shell in a hot chamber will do u in as well
My hunting rigs run approximately 30-50 avg to support adiquate groups.
Powder/ temp/ big keys to the puzzle.
Leaving a shell in a hot chamber will do u in as well
Have you ever heard of MagnetoSpeed chronographs? I've been using one for a couple months now, it uses 2 magnetic sensors instead of optical sensors to measure the velocity at the muzzle (unit is strapped to the barrel). I chose it over light-sensing chrons for all the reasons you mentioned above, but was wondering if you had any experience with them specifically? It seems like I've been getting fairly repeatable results with mine, so long as the trigger setting is set up right. Your post definitely re-enforces my choice of chronograph for me anyways.
