Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Reloading

Reloading Techniques For Reloading


Reply

Erratic Chronometer Readings

 
LinkBack Thread Tools Display Modes
  #8  
Old 04-07-2013, 07:13 PM
Silver Member
 
Join Date: May 2010
Location: Central Ohio
Posts: 253
Re: Erratic Chronometer Readings

Lot of good answers there. What is your twist rate?
I am in agreement that you need heavier bullet for the 300rum, try 215 or 230 hybrids, 208 amax, using H1000.
Reply With Quote
  #9  
Old 04-07-2013, 07:32 PM
Bronze Member
 
Join Date: Dec 2011
Location: S/E Kansas
Posts: 97
Re: Erratic Chronometer Readings

My experience with the F1 Chrony. I was getting readings as low as 1300 FPS with my known prairie dod loads that should have been reading 2590 FPS. I had to adjust the height of the chrony so the bullet was passing somewhere between 4-6" above the eyes of the crony. My F1 worked great when I learned how to use it. In your case I really don't feel this is the problem but it easy to check.
Reply With Quote
  #10  
Old 04-07-2013, 07:43 PM
Junior Member
 
Join Date: Apr 2013
Posts: 4
Re: Erratic Chronometer Readings

Quote:
Originally Posted by 375fan View Post
Lot of good answers there. What is your twist rate?
I am in agreement that you need heavier bullet for the 300rum, try 215 or 230 hybrids, 208 amax, using H1000.
Twist rate is 1 in 10
Reply With Quote
  #11  
Old 04-09-2013, 10:39 AM
Platinum Member
 
Join Date: May 2008
Location: South of Canada and North of Wyoming
Posts: 5,954
Re: Erratic Chronometer Readings

I find chronographing on overcast days to give me the best results. That is why I will soon be ordering an acoustical chrony which is completely independent of light conditions. I have seen 50-60 fps jumps from overcast to sunny conditions. A couple of years ago, I got a second chrony and set it right behind the first. Readings were anywhere from 5 to 70 fps different on a sunny day.

A saw a guy at the range a few days ago with some battery operated LED lights taped to the top of his sky screens. He said they worked very well for him. More consistant light.

Changing the battery is another good suggestion.

That said, you may indeed have a large ES with your load for whatever reason, but chances are that some of the low and high reading are in error. Hard to say.

I agree that heavier bullets are best to get the most out of a RUM, but I have shot 180 E-Tips out of mine with numerous sub .5 MOA groups. This is out of a Sendero.

Your accuracy and ES could be due to any number of things.

How accurate is your scale? I had a 10-10 start acting up on me once.

Have you damaged your crown?

Action screws and bedding?

Scope and mount screws?

Scope?

Fouled bore?

Throat erosion? How many rounds down your 300 RUM? They can go quick if you shoot them hot.

It could be any of these or something else or a combo of things.
__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams
Reply With Quote
  #12  
Old 04-09-2013, 12:34 PM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,273
Re: Erratic Chronometer Readings

Quote:
Originally Posted by MontanaRifleman View Post
I find chronographing on overcast days to give me the best results. That is why I will soon be ordering an acoustical chrony which is completely independent of light conditions. I have seen 50-60 fps jumps from overcast to sunny conditions. A couple of years ago, I got a second chrony and set it right behind the first. Readings were anywhere from 5 to 70 fps different on a sunny day.

A saw a guy at the range a few days ago with some battery operated LED lights taped to the top of his sky screens. He said they worked very well for him. More consistant light.

Changing the battery is another good suggestion.

That said, you may indeed have a large ES with your load for whatever reason, but chances are that some of the low and high reading are in error. Hard to say.

I agree that heavier bullets are best to get the most out of a RUM, but I have shot 180 E-Tips out of mine with numerous sub .5 MOA groups. This is out of a Sendero.

Your accuracy and ES could be due to any number of things.

How accurate is your scale? I had a 10-10 start acting up on me once.

Have you damaged your crown?

Action screws and bedding?

Scope and mount screws?

Scope?

Fouled bore?

Throat erosion? How many rounds down your 300 RUM? They can go quick if you shoot them hot.

It could be any of these or something else or a combo of things.
I bought an acoustic Superchrono for much the same reasons. I have now used it about four or five times and I'm not convinced that it's the answer that it's cracked up to be. The specs are .5-1% error and that's about what I can see best case if everything is lined up perfectly. At 3000 FPS that 15-30 FPS error. It's better I think for getting a true velocity average regardless of light conditions, but not for establishing ES. For my serious ballistic work, I think I'm going to stick with my Ohler on overcast days. IMO
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
  #13  
Old 04-09-2013, 01:07 PM
Gold Member
 
Join Date: Feb 2012
Posts: 806
Re: Erratic Chronometer Readings

heres what id try first IF YOUR NOT ALLREADY SHOWING PRESSURE SIGNS. Bump it up another grain of powder to raise the pressure a tad to see if that helps that 1000 burn a bit better. If you see some improvement try another 1/2 a grain at a time till either it cures it or you see pressure signs. Trying another primer might work too. Maybe a cci mag rifle but i have to doubt it as ive had better luck lighting of real slow powders with the primers your using. Only differnce is i use the match version (which might be worth a try too if you can find some). Another thing id try too is to shoot a different rifle, one you know has nice tight spreads to see if it is your chonograph giving bad readings.
Reply With Quote
  #14  
Old 04-09-2013, 01:32 PM
Platinum Member
 
Join Date: May 2008
Location: South of Canada and North of Wyoming
Posts: 5,954
Re: Erratic Chronometer Readings

Quote:
Originally Posted by Greyfox View Post
I bought an acoustic Superchrono for much the same reasons. I have now used it about four or five times and I'm not convinced that it's the answer that it's cracked up to be. The specs are .5-1% error and that's about what I can see best case if everything is lined up perfectly. At 3000 FPS that 15-30 FPS error. It's better I think for getting a true velocity average regardless of light conditions, but not for establishing ES. For my serious ballistic work, I think I'm going to stick with my Ohler on overcast days. IMO
Have you shot the acoustic chrony against the Oehler and if so, what were the results? My smith has an Oehler and I was going to have him compare when I got the acoustic. Really nice not having to worry about light, and having a large shooting window and not having to assemble anything to set it up.
__________________
- Mark

You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Current Poll
Do you archery hunt for elk?
YES - 30.06%
49 Votes
NO - 54.60%
89 Votes
Not yet, but I plan to. - 15.34%
25 Votes
Total Votes: 163
You may not vote on this poll.

All times are GMT -5. The time now is 05:04 PM.


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