Chronograph velocities versus "Book" & factory velocities

[GAnderson]

So as to not hi-jack the other thread on chronographs, I just purchased a new V3 Magnetospeed and have some questions regarding the published "book" velocities for a given load and what I am registering on the V3. The same applies for the printed velocity on factory ammo boxes. I have a .204 and am experiencing approximately 75fps slower than what book velocities are for various loads....same barrel length, same twist and same components as the "book" says. I know some barrels can be faster than others and that some "books" tend to be "faster" than they really are.....but just wondering if this is typical. The V3 is the greatest thing since sliced bread and is very consistent with no errors....so I am not questioning the V3's quality. Just curious as to what the rest of you may have found. The factory Hornady 204/32gr vmax load with a velocity of 4225fps printed on the box is only going 3971 over my V3....254fps difference....have others sent this ammo over there chrono with similar results? As stated before, the V3 is fast, easy and a breeze to use and I am satisfied with it, so this is not meant to be a "bashing" of the unit.....just wanted to see what others experience against "the books". Thanks

Gene

 

[rduckwor]

I don't think I have ever chronoed a load that gave "book" or "box" velocity.

Just the way it seems to work out.

RMD

 

[CatShooter]

No two guns will give the same velocities from the same ammunition... even if the barrels are the same length.

 

[CaptainMal]

Too many variables from one test rifle to all the rifles in the "real world".

Decades of chronographing clearly has shown me you cannot expect published or "book" results. Sometimes, such as my 17 HMR, the velocities are even higher than published.

 

[dcbais]

Chronograph velocities versus "Book" & factory velocities
Hi, this is my first post so hope I don't come off sounding like a know it all.
Velocity is just what it is. A number to reference . I like to load too a node.
That depends (not the ones you wear) on the rifle. but to answer you question. I use the velocity from factory ammo only if I am trying to match its accuracy. I have never had my loads equal the book velocities.
Dave

 

[UltraBR30]

From book to actual, very common for me to see the book velocities exceed what I get in actuality. And excessively often enough. Just as find there Maximum to be off (even excessively) to actual. I view reloading data in the manuals as reference only, not factual.
Philip

 

[chkunz]

All instrumentation has some accuracy (+/-) associated with the reading. Professional instrument engineers use calibration techniques to determine the accuracy of the instruments they use (they normally refer to this as the instrument uncertainty rather than accuracy). The instrument manufacturers normally give some stated accuracy for their product. I am wondering what this accuracy band is for the chronographs that handloaders use and if it is significant relative to the discrepancies that folks are seeing.

 

[CatShooter]

All instrumentation has some accuracy (+/-) associated with the reading. Professional instrument engineers use calibration techniques to determine the accuracy of the instruments they use (they normally refer to this as the instrument uncertainty rather than accuracy). The instrument manufacturers normally give some stated accuracy for their product. I am wondering what this accuracy band is for the chronographs that handloaders use and if it is significant relative to the discrepancies that folks are seeing.

It is not the chronographs... it is the variations in barrels and chambers that are responsible for the discrepancies in velocities.

 

[michaelnel]

I figure the velocity numbers for commercial ammo come from the Marketing Department, not the Velocity Testing Department.

 

[GAnderson]

Thanks for the replies....I pretty much figured that the book velocities "could" be a little biased as to what our chronographs give us in the real world. Like I said, most of my loads were around 70-75 fps slower than the books.....that is close enough for me as a reference and given the different variables, this is acceptable. I was a little surprised though that the factory hornady ammo that printed 4225fps on the box was so far off ....254fps. If it too had been around 70-75fps slower I wouldn't have given it much thought....that is why I was wondering if anybody had tried that factory ammo over their chrono with similar results.

Gene

 

[madderg]

Modern loading data will always go to the light side...lawyers