Long Range Hunting Online Magazine


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

Reloading Techniques For Reloading


Reply

Which Chronograph?!??

 
LinkBack Thread Tools Display Modes
  #29  
Old 05-05-2013, 12:32 PM
Platinum Member
 
Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,452
Re: Which Chronograph?!??

Quote:
Originally Posted by Greyfox View Post
My understanding is that the bullet will loose velocity from the the time it exits the barrel. It will not accelerate. In order to have exact muzzle velocity you must add back the velocity that is lost from distance that the chronograph is placed. Some ballistic programs accommodate this. It's not much, but none the less, once accounted for there is no difference using the velocities from either chronograph as long as they are accurate readings. IMO.
I've always heard that a bullet accelerates for about 25 or 30 feet, then starts dropping off. I never bothered to prove or disprove this, but thinking about it from the physics end it should accelerate a little bit. How far I can't say. A good way to think about it is that if the bullet is still climbing (with the barrel level to the earth) then it has to still be gaining rpm's. Plus there is the resistence from the barrel's bore and rifeling with a build up of gas pressure.

gotta think about that one as you maybe right.
gary
Reply With Quote
  #30  
Old 05-05-2013, 05:05 PM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,199
Re: Which Chronograph?!??

Quote:
Originally Posted by Trickymissfit View Post
I've always heard that a bullet accelerates for about 25 or 30 feet, then starts dropping off. I never bothered to prove or disprove this, but thinking about it from the physics end it should accelerate a little bit. How far I can't say. A good way to think about it is that if the bullet is still climbing (with the barrel level to the earth) then it has to still be gaining rpm's. Plus there is the resistence from the barrel's bore and rifeling with a build up of gas pressure.

gotta think about that one as you maybe right.
gary
Gary, I'm not so sure now. I did some searching on the topic. Turns out, it'a controversial topic. I had read a few times in the past that when a chronograph is placed 10-20 feet from the muzzle that you needed to add back some velocity to get the true muzzle velocity since the bullet slows down from air resistance immediately. Turns out the Army claimed as a result of tests years ago that the bullet did speed up when it left the.muzzle for few inches due to gases still pushing on the bullet. Since that report there has been disputes. I would think that a muzzle break would reduce this gas effect yet there are claims that there is no effect on velocity. Anyway, it seems it's an open question unless someone chimes in with additional information. I'm not so sure that it will make a big difference anyway.
Art
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
  #31  
Old 05-06-2013, 10:44 AM
Platinum Member
 
Join Date: Jun 2010
Location: greenwood, IN
Posts: 3,452
Re: Which Chronograph?!??

Quote:
Originally Posted by Greyfox View Post
Gary, I'm not so sure now. I did some searching on the topic. Turns out, it'a controversial topic. I had read a few times in the past that when a chronograph is placed 10-20 feet from the muzzle that you needed to add back some velocity to get the true muzzle velocity since the bullet slows down from air resistance immediately. Turns out the Army claimed as a result of tests years ago that the bullet did speed up when it left the.muzzle for few inches due to gases still pushing on the bullet. Since that report there has been disputes. I would think that a muzzle break would reduce this gas effect yet there are claims that there is no effect on velocity. Anyway, it seems it's an open question unless someone chimes in with additional information. I'm not so sure that it will make a big difference anyway.
Art
just thinking, and have not ever given thought to prove or disprove the thought. The Earth's gravity is one of the few true constants we can work with. Everyone knows that a projectile travels in an arc. In doing so we are somewhat overcomming gravitational pull (the one constant). A major factor to this is the rotational speed speed of the mass in travel. Now it would appear to me that with the barrel (in this case) set dead parallel to the Earth's surface, the peak of the arc should be the highest rate of spin on the bullet. As it drops off (going back down) the rate of spin should be decreasing. Thus relating to loss of veocity.

Back to the Army. They use an Ohler 43 (nothing like the 35P) and another super sophisticated rig to figure the B/C of their rounds (including tank ammo and small arms). If I remember right they us more than one in tandum.

what do you think?
gary
Reply With Quote
  #32  
Old 05-06-2013, 11:11 AM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,199
Re: Which Chronograph?!??

Quote:
Originally Posted by Trickymissfit View Post
just thinking, and have not ever given thought to prove or disprove the thought. The Earth's gravity is one of the few true constants we can work with. Everyone knows that a projectile travels in an arc. In doing so we are somewhat overcomming gravitational pull (the one constant). A major factor to this is the rotational speed speed of the mass in travel. Now it would appear to me that with the barrel (in this case) set dead parallel to the Earth's surface, the peak of the arc should be the highest rate of spin on the bullet. As it drops off (going back down) the rate of spin should be decreasing. Thus relating to loss of veocity.

Back to the Army. They use an Ohler 43 (nothing like the 35P) and another super sophisticated rig to figure the B/C of their rounds (including tank ammo and small arms). If I remember right they us more than one in tandum.

what do you think?
gary
My understand
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
  #33  
Old 05-06-2013, 11:38 AM
B23 B23 is offline
Gold Member
 
Join Date: Oct 2008
Location: Spokane, Wa.
Posts: 928
Re: Which Chronograph?!??

It's always been my understanding that the only reason a bullets path has an "arch" to it is because the barrel was aimed up instead of in a horizontal line to the target and that if the barrel is held horizontal the bullet is on a steady course to the ground.
Reply With Quote
  #34  
Old 05-06-2013, 12:40 PM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,199
Re: Which Chronograph?!??

Quote:
Originally Posted by B23 View Post
It's always been my understanding that the only reason a bullets path has an "arch" to it is because the barrel was aimed up instead of in a horizontal line to the target and that if the barrel is held horizontal the bullet is on a steady course to the ground.
I don't know what happened to my last post but this post reflects my understanding as well. Gravity takes effect immediately upon the bullets exit .
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
  #35  
Old 05-06-2013, 12:56 PM
Platinum Member
 
Join Date: Jan 2008
Location: Northeast
Posts: 2,199
Re: Which Chronograph?!??

Quote:
Originally Posted by B23 View Post
It's always been my understanding that the only reason a bullets path has an "arch" to it is because the barrel was aimed up instead of in a horizontal line to the target and that if the barrel is held horizontal the bullet is on a steady course to the ground.
I don't know what happened to my last post but this post reflects my understanding as well. Gravity takes effect immediately upon the bullets exit .
__________________

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Current Poll
Where in the US do you live?
West of the Mississippi River - 60.09%
783 Votes
East of the Mississippi River - 37.61%
490 Votes
On the Mississippi River on a houseboat - 2.30%
30 Votes
Total Votes: 1,303
You may not vote on this poll.

All times are GMT -5. The time now is 02:43 AM.


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