Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Rifles, Bullets, Barrels & Ballistics

Rifles, Bullets, Barrels & Ballistics Applied Ballistics


Reply

Differences in Chronograph Readings

 
LinkBack Thread Tools Display Modes
  #1  
Old 04-14-2013, 10:31 AM
Gold Member
 
Join Date: Jun 2004
Location: Worland, Wyoming
Posts: 592
Differences in Chronograph Readings

Went to the range yesterday to work on my drop charts with 215 Bergers in my 300rum. I set up both of my chronographs two feet apart about 10 feet in front of the muzzle. Older chronograph is a pro chrono, and the newer one bought last year is a Chrony F-1.

First shot showed 3075 through the Pro Chrono and 3163 through the Chrony. Then I put the 338rum in front of the chronographs and recorded 2780 through the Pro Chrono and 2870 through the Chrony.

My 338 rum loads have been proven out to 1250 and the velocity comes out to 2830 with the 300 gr Berger OTM Hybrid gen II.

With the numbers entered into exbal on my PDA, using 3025 as the velocity for the 300 rum with the 215 berger I am hitting a consistant 3 inches low at 690 yards. I need an additonal .25 moa up to hit the mark and to get there, I think my calculated velocity needs to go down to 3000.

Anyone else out there with Chrony's have them showing fast like this?
__________________
Remington model 700 300 RUM LH 26" rem ss/blued receiver lam stock 215 Berger @3025/180 NAB @3300
Remington model 700 338 RUM LH 27" Broughton 5C 225NAB@3300 /300gr Berger@2830
Savage LH 22-250
Reply With Quote
  #2  
Old 04-15-2013, 06:54 PM
Bronze Member
 
Join Date: Apr 2008
Posts: 32
Re: Differences in Chronograph Readings

I'm glad to see someone post this subject. I was going to a long time ago but just didn't want to get into it.

My results with these two brand name chronographs has been almost identical. I have tried three different Chronys, two Pro Chronos and two Oehler 35 Ps. In every case, the ProChrono read very close to the Oehler; within single digits. The Chrony would read up to 110 fps faster depending on the muzzle velocity of the load. It didn't matter which chronograph was in front. It seems like a percentage difference. The higher the muzzle velocity the more the difference.

I suppose one could argue the Chrony is right and the others are wrong but that's not likely. I develop my drop charts using data from the Oehler or Pro Crono and everything seems to work out correctly.

Thank you for posting this.
Reply With Quote
  #3  
Old 04-15-2013, 07:19 PM
Gold Member
 
Join Date: Jul 2007
Location: Billings, Mt
Posts: 810
Re: Differences in Chronograph Readings

Been there - done that. My chrony read high compared to back to back with other chronographs as well as actual field testing. Dang near put a bullet through it one day. After settling down after a few days I called chrony. Sent it in and they re-calibrated it.
By the way - they test/check/calibrate with a pellet rifle.
Mine read consistently 35 fps high at 2850 fps.
It is caused by the two reading eyes (little black boxes) being too close together or too far apart.
Reply With Quote
  #4  
Old 04-15-2013, 07:25 PM
Gold Member
 
Join Date: Jun 2004
Location: Worland, Wyoming
Posts: 592
Re: Differences in Chronograph Readings

The reason I bought the Chrony was because I have a friend who has a Chrony and he was recording faster velocities than I was, plus I have a loose wire on the pro chrono and sometimes it doesn't want to turn on. I have another friend that just bought a new chrony and he is recording some abnormally fast velocities from the 300 wby with 215 Bergers. Since he is new to long range shooting, I don't want him to get all frustrated when his drops don't match his G-7 range finder. In the past, it was always easy to blame the bullet maker's B.C. as being wrong to validate the velocity that was read with the chronograph. Now I have come to the conclusion that what the chronograph says really doesn't matter, get the velocity to match the drops and go with it. It just annoys me to buy a piece of equipment and not have it even be close to what it should be. I think the chrony is going on ebay for sale and I am going to keep my eyes open for an ohler. It is kind of hard to strive for a gun that shoots sub 1/2 moa only to have a chronograph that is the equivilent of shooting a 3 inch moa.
__________________
Remington model 700 300 RUM LH 26" rem ss/blued receiver lam stock 215 Berger @3025/180 NAB @3300
Remington model 700 338 RUM LH 27" Broughton 5C 225NAB@3300 /300gr Berger@2830
Savage LH 22-250
Reply With Quote
  #5  
Old 04-15-2013, 07:42 PM
Silver Member
 
Join Date: Apr 2008
Location: Dillon Mt
Posts: 170
Re: Differences in Chronograph Readings

Quote:
Originally Posted by cowboy View Post
Been there - done that. My chrony read high compared to back to back with other chronographs as well as actual field testing. Dang near put a bullet through it one day. After settling down after a few days I called chrony. Sent it in and they re-calibrated it.
By the way - they test/check/calibrate with a pellet rifle.
Mine read consistently 35 fps high at 2850 fps.
It is caused by the two reading eyes (little black boxes) being too close together or too far apart.
Do you think it is possible to not have it opened all the way and have the eyes looking a bit inward (that would be crosseyed). I have discovered mine lying from time to time and this makes me wonder if not setting it up the same every time could be it.
Cliff
Reply With Quote
  #6  
Old 04-15-2013, 08:05 PM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,420
Re: Differences in Chronograph Readings

Quote:
Originally Posted by Cornfield Flats View Post
I'm glad to see someone post this subject. I was going to a long time ago but just didn't want to get into it.

My results with these two brand name chronographs has been almost identical. I have tried three different Chronys, two Pro Chronos and two Oehler 35 Ps. In every case, the ProChrono read very close to the Oehler; within single digits. The Chrony would read up to 110 fps faster depending on the muzzle velocity of the load. It didn't matter which chronograph was in front. It seems like a percentage difference. The higher the muzzle velocity the more the difference.

I suppose one could argue the Chrony is right and the others are wrong but that's not likely. I develop my drop charts using data from the Oehler or Pro Crono and everything seems to work out correctly.

Thank you for posting this.

I also have these there plus a Superchrono Acoustic. The Chrony reads typically 75-100 FPS faster then the others which ate close given it an overcast day. This occurs with both my 300WM and 6.5x284.
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
  #7  
Old 04-15-2013, 09:23 PM
Gold Member
 
Join Date: Jul 2007
Location: Billings, Mt
Posts: 810
Re: Differences in Chronograph Readings

Quote:
Originally Posted by CliffM View Post
Do you think it is possible to not have it opened all the way and have the eyes looking a bit inward (that would be crosseyed). I have discovered mine lying from time to time and this makes me wonder if not setting it up the same every time could be it.
Cliff
All I can tell you is that setup with the Chrony's is critical. I like to run 2 chronographs back to back to give me a warm and fuzzy feeling.

With the one F-1 that I have I can only tell you what I do to not get frustrated.

1) I set up the F-1 at a minimum of 15 ft. from the muzzle of rifle - and I measure this with a tape measure, make note of it, and after a session I plug into ballisitic calculator to get true muzzle velocity. At 2800+ it usually adds about 7 fps to actual reading on chrony with 168 Berger VLD's on a .284 bullet. With a heavy boomer with brake I set up chrony at 20 ft. from muzzle..

2) I bought an old style folding 3 legged surveyors tripod at a pawn shop (20 bucks) that is sturdy as all get out and adapted a bolt/nut to tripod head to fit my chrony. After setting up chrony the correct distance I want, I level it both ways with a 6" torpedo level. I think since I started doing this it has made a world of difference in that I can't remember the last ERR reading that I got.

Having a very solid base (tripod), keeping it far enough away to prevent any muzzle blast having an effect, and getting it perfectly level has now allowed my cheap chrony to run right with some of the more expensive units.

I would encourage you to send your chrony back to get re-calibrated if it is truly reading high/low. They are good people to work with and it only cost me postage one way. Keep in mind that these units are acceptable if they read within + or - 3%. For me that is not acceptable as plus or minus 3% of 3000 fps is 90 fps at it's worse senario.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes



All times are GMT -5. The time now is 10:23 AM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC