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Have any of you folks ever checked the accuracy of your chronies, and if so, how? I've got a shooting chrony, good, or bad? The only way I ever checked mine was to shoot some top rated shotgun ammo with published velocities printed on the box. Of those I'm usually within +/- 20fps.
That said, rifle velocities can be off, usually lower, buy up to 200fps with some powders and very close to published data with others. With shotguns, my velocities can be off up to 150fps, higher or lower, with published data followed exactly:eek:.
I loaded some hevi-shot loads per Alliant data and was running at 1420fps vs. their 1367fps, so I gave them a call. After the usuall 3rd. degree, he snickered at my $90 chrony vs. his mega zero $ laboratory housed chronograph. After all that, he said "shoot em, but they are shooting at 1367fps".
So, what are your thoughts?
 
Light conditions and other variables can affect the chronys that use light.

The Magnetospeed and Labradar seem to be better at more accurately gauging true velocity.
 
If you are trying to duplicate published data, You would also need to duplicate the conditions it was recorded at. Temp, Elevation, Humidity, Test barrel or fired from a gun, etc.... I have found a lot of factory ammo will publish data that can't be duplicated out of a lab.
On the other hand when reading factory data if one lists 1200 fps and another lists 1300 I can usually confirm that one is about 100 FPS faster than the other.

I have talked to ammo company's about their ammo and had engineers laugh at my $100 chronos. They say how dare you call my ammo into question that I test on multi thousand dollar equip.... Bla Bla Bla...

What you can't do is set an exact speed. What your chrono can do is help you find inconsistencies. If an ammo is consistent you can easily predict where a shot will strike.

Good Luck DR
 
I'd say mine is accurate enough.

Coupled with the JBM computer and known bullets with SD's and drag... computer and real life were really close.
 
Mine is pretty accurate, I've used the velocity it's given me to predict drop for shots out to 700+ yards and it was good.

I frequently get different velocities than what the books say I should/could get. Usually there is some other variable at play though, bbl length, twist, seating depth. I just figure out what velocity I need, choose the load that gets me closest at safe pressure, and go from there.
 
I have a Shooting Chrony. Like jordanka16, I have taken the speeds it gives me at 3 yards and using Sierra's ballistic chart, plotted drops at 300 and 400 yards. When shooting at these distances, the bullets landed where they should, which leads me to believe that the chrono is reading correctly, or so close for the difference to be insignificant.

My first experience with a chrono was shooting some handloads in 41 Mag years ago. I was very disappointed in the results as the book "told" me I should be getting alot more out of them than I was.

As to the OP's question, the statement made by the person at Alliant is not only arrogant, it's ignorant.
I've loaded up with some powders that won't reach the listed velocity, but in the same gun, load up a different powder and it's faster than what's listed. My 22" barreled 30-06 wouldn't quite match what either Sierra or Nosler show for a 180gr bullet over RL22. That makes sense because they test in a 24" barrel. But that same gun re-chambered to 30-06AI, still a 22" barrel and burning RL22, will run the numbers generated in a 24" barrel.

Ballistics, especially internal ballistics, is not an exact science.
 
Thanks for the input guys. Sounds like you are getting some of the same variables I have discovered. What I'm concerned about is if I shoot a load of 12ga. 11/4oz at 1330 published at say 10500psi and it shoots over my chrony at 1400 plus, am I at dangerous pressures?
I've been reloading long enough that I can read rifle and pistol loads pretty well. Where this is going is I'm starting to get into loading steel shot for waterfowl and I want to be shooting in the 1500fps plus range so I'm not getting so many cripples. Including me.
 
Thanks for the input guys. Sounds like you are getting some of the same variables I have discovered. What I'm concerned about is if I shoot a load of 12ga. 11/4oz at 1330 published at say 10500psi and it shoots over my chrony at 1400 plus, am I at dangerous pressures?
I've been reloading long enough that I can read rifle and pistol loads pretty well. Where this is going is I'm starting to get into loading steel shot for waterfowl and I want to be shooting in the 1500fps plus range so I'm not getting so many cripples. Including me.

I would only be concerned if you're over the max published load. Something else might be giving you more velocity, wad design, choke?
 
Nah, following the steel shot data exactly as published right down to weighing every powder and shot charge. It's tedious, but I'm too stubborn to shoot factories for anything other than aquiring brass or hulls.
 
I've never reloaded for shotguns, but if I exceeded listed velocities in a rifle, I'd be starting to second guess myself. If I wasn't close to max powder charge I wouldn't sweat it too much, but if I was I'd break one or two cartridges down and re-weigh the charges. I usually don't get that far before experiencing other pressure signs.

Is it possible your shell is different? Less powder space raises pressures.
 
jrd,

If you are getting + or - 20 Fps.
Your Chronograph is working very well. And the loads are very good as well!
If you contact technical at a ammunition manufacturer for their information addressing a specific LOT's # and Fps. They will usually advise you within 50 Fps what the average of that specific LOT# is. So within + or - 20 Fps is excellent on the part of your Chronograph IMO. My chronograph will also slightly vary since there is some variables of each round. Including maybe an extra 1/10 of grain or less when the powder is dropped, crimp on the case or shell, capacity variance of a case or shell. And other slight variances which can be expected. And as Orygun mentioned in order to get exactly what a manufacturer mentions regarding Fps from a loading manual. There will certainly be a variances. Because of many variables as barrel length, bore, chamber tolerance, the temperature, atmospheric and other conditions. So you would almost have to use the same gun they used plus the same atmospheric and other conditions they used including cases/shells to be exact. *Otherwise everything would have to be *Exactly the same to obtain their specifications when testing Fps.

Sniper03
 
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Nah, shotgun data lists every component right down to the hull, wad, powder and charge, and primer and has the pressure listed with every load. With so many warnings about steel shot I follow the data exactly. But, with some loads I'm getting velocities up to 150fps over published. With shotgun data there is no "working up a load. At least with steel.
 
Nah, following the steel shot data exactly as published right down to weighing every powder and shot charge. It's tedious, but I'm too stubborn to shoot factories for anything other than aquiring brass or hulls.

By any chance, did you chrono any of those factory loads? Might be nice to see how fast your gun shoots ammo of a "known" velocity.
 
I have taken the speeds it gives me at 3 yards and using Sierra's ballistic chart, plotted drops at 300 and 400 yards. When shooting at these distances, the bullets landed where they should, which leads me to believe that the chrono is reading correctly, or so close for the difference to be insignificant.
Science!
 
jrd,

If you are getting + or - 20 Fps.
Your Chronograph is working very well. And the loads are very good as well!
If you contact technical at a ammunition manufacturer for their information addressing a specific LOT's # and Fps. They will usually advise you within 50 Fps what the average of that specific LOT# is. So within + or - 20 Fps is excellent on the part of your Chronograph IMO. My chronograph will also slightly vary since there is some variables of each round. Including maybe an extra 1/10 of grain or less when the powder is dropped, crimp on the case or shell, capacity variance of a case or shell. And other slight variances which can be expected. And as Orygun mentioned in order to get exactly what a manufacturer mentions regarding Fps from a loading manual. There will certainly be a variances. Because of many variables as barrel length, bore, chamber tolerance, the temperature, atmospheric and other conditions. So you would almost have to use the same gun they used plus the same atmospheric and other conditions they used including cases/shells to be exact. *Otherwise everything would have to be *Exactly the same to obtain their specifications when testing Fps.

Sniper03

Hey Guys,
FYI...info
As a hand loader for all my bench shooting from my .342, I learned a little trick. I was getting good grouping's shooting the 3 loads I like for my .243, but I could not figure out why my ballistics were not closer. I use good Hornady quality loading equipment, and very consistent power loads, and Hornady Bullets. I size, tumble, and clean all my brass very well, and double check the bullet necks for proper sizing.
Well, I found out by bottle brushing the neck of the cases with the same bore brush I use for the Barrel, it would remove caked on and hardened contaminates inside the case. This was changing the crimping pressure on the bullets even tho I thought they were very clean. The little film was enough to make crimping pressure diffrent. I also found out it is better to do it before tumbling rather then after.
Results: My ballistics were much closer, but no change in accuracy. Since I was happy with my grouping's I felt much better that the rounds were all going about the same in my...Chronograph
It was worth the effort and makes me know it was not me!
Larry243
 
I shot my LabRadar in tandem with my CED Millineum. The LR at the muzzle and the CED at 10'. The readings were reflective shot to shot down to the calculated slowing down of the 10 foot distance. The LR lets me check at various ranges and they were so close as to be identical.

Greg
 

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