Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Hunting > Long Range Hunting & Shooting

Long Range Hunting & Shooting Nightforce Optics


Reply

**HELP** Need to understand trajectory(heavy VS light) in bullets.

 
LinkBack Thread Tools Display Modes
  #8  
Old 12-12-2010, 04:27 PM
Platinum Member
 
Join Date: Apr 2010
Location: Allen, TX
Posts: 2,608
Re: **HELP** Need to understand trajectory(heavy VS light) in bullets.

freebird63,

Thanks for clarifying.

I have the book you mentioned. It's an excellent resource and I agree with you and the author.

I was just pointing out that boat tails and VLD bullets don't have the advantage at close range/high velocity over flat base bullets. So, that may be the origin for the notion of "going to sleep". Some people use that as an excuse for poor accuracy at short range thinking that their accuracy will improve over distance. I shure don't subscribe to that theory.

Nonetheless, it's my understanding that flat base designs dominate 100-200yd benchrest as compared to boat tail/VLD designs which dominate 600+yd competition.

My thinking is that bullet shape has more to do with trajectory than weight (heavy vs light). Weight has everything to do with energy. And, expansion is what destroys tissue and transfers energy.

thanks,
richard
Reply With Quote
  #9  
Old 12-12-2010, 06:15 PM
Gold Member
 
Join Date: Jun 2009
Location: Afognak Island, Alaska
Posts: 502
Re: **HELP** Need to understand trajectory(heavy VS light) in bullets.

Quote:
Originally Posted by freebird63 View Post
Now about that idea of a bullet going to sleep, I am still on the fence about that one. But if you have the book called "precision shooting at 1000 yards", on page 224 he mentions the idea of a bullet going to sleep and says its hogwash and it always makes him laugh when someone mentions that.
YouTube - Pitching and Yawing of a bullet
Here's a video that explains the pitching and yawing of a bullet in flight. It is fairly common to shoot, say, a 1.5moa group at 100 yards and a 1moa group at 300. I've seen this happen all the time. I'm pretty sure it's because boatails do indeed go to sleep.

Quote:
Originally Posted by FREEBIRD63 View Post
Also somewhere I saw, it might have been on the military channel, a sniper talking about how the bullet spin pulls a bullet back down towards earth.
Actually, with a right-hand twist, the bullet climbs up if the wind is coming from the right and spins down if the wind is coming from the left. It's called spindrift. The riflings score little groves in the bullet that act like fins. If the wind is coming from the right the high pressure is on the right side of the bullet. The bullet is spinning clockwise and grips(?) the wind better on the right side. It's just the opposite for a left to right wind.
I hope I explained that well enough. I can picture it in my head but I don't know if I can explain it very well.
__________________
Long Range Sickle

Last edited by LRSickle; 12-12-2010 at 06:21 PM.
Reply With Quote
  #10  
Old 12-12-2010, 07:11 PM
Platinum Member
 
Join Date: Apr 2010
Location: Allen, TX
Posts: 2,608
Re: **HELP** Need to understand trajectory(heavy VS light) in bullets.

Great video. Everyone that's interested might want to read up on the subject.

It appears the video came from...
Homepage of Bryan Litz - A Bravenet.com Hosted Site

According to Bryan Litz, the author of the computer simulation in the video, "I tried many different things like this, simulated hundreds of 5, 10, and 20 shot groups. Nothing produced smaller angular groups at longer range. [...] Just to be clear about the conclusions of the modeling: The phenomemon of smaller angular groups at longer ranges was not disproven. The only thing I've shown is that if the phenomenon actually happens, epicyclic swerve is not the cause of it."

So, while he didn't disprove it. I'd be keen to read more about what really happens. I do know that some people beleive in it strongly. So, there must be a reason why they beleive it and why it occurs.

A less scientific phenomenon that I've observed is, "aim small, miss small." My 14yo son is impatient and doesn't concentrate at short range where he knows it's a kill shot every time. But, he's really focused at longer ranges. I can show you targets where he's shot 1" groups at 100yds and 3" groups at 580 yds. I don't have enough samples to make a statistical inference and shooter concentration that I've attributed this to isn't the same as the bullet going to sleep. But, the point being that there are many variables that result in the POI whether it be short or long range.

As to the rise/fall due to spin and wind direction, I have seen that written about in some fairly authoritative places.

thanks,
richard
Reply With Quote
  #11  
Old 12-12-2010, 08:06 PM
Platinum Member
 
Join Date: Jun 2001
Location: Potomac River
Posts: 5,059
Re: **HELP** Need to understand trajectory(heavy VS light) in bullets.

Quote:
Explain to me why do we use the heavier bullets as opposed to the lighter for long range. In ending I do understand wind drift in the lighter VS heavier, but trying to understand what's stated up top thanks!
OK, you asked a certain question and what follows is the correct answer.

The ballistic coefficient is the number which determines the trajectory and it is is composed of two terms. First term is a shape or form factor and the second term is sectional density or weight.

I would invite you attention to a most useful reference

exterior ballistics

The Sierra Exterior Ballistic document is very worthwhile reading. And after a few years of shooting long range you should read it again as some of the small details will be fresh and new and you will learn a lot more once again. The guys who wrote it did a good job.



I would just add two notes----
1. High sectional density is not only good for the BC but is good for penetrating animals.
2. A copper bullet with the same shape factor as a gilded lead bullet will have a low SD and low BC. Conversely a heavy bullet with a round nose will have a high SD but poor shape factor and therefore a low BC. There is a time and place for each type of bullet. The buffalo I killed was with a round nosed bullet at 50 yards from the same rifle I used to shoot high BC bullets 1000 yards.
__________________
The Smokin Fur Rifle Club
Reply With Quote
  #12  
Old 12-12-2010, 08:22 PM
Platinum Member
 
Join Date: Apr 2010
Location: Allen, TX
Posts: 2,608
Re: **HELP** Need to understand trajectory(heavy VS light) in bullets.

excellent resource
thanks!!!
Reply With Quote
  #13  
Old 12-13-2010, 12:38 AM
Gold Member
 
Join Date: May 2006
Location: Oklahoma City Ok
Posts: 526
Re: **HELP** Need to understand trajectory(heavy VS light) in bullets.

Awesome!!!!!!!!!!!!
Reply With Quote
  #14  
Old 12-13-2010, 02:28 AM
Silver Member
 
Join Date: Dec 2009
Location: Boise, Idaho
Posts: 483
Re: **HELP** Need to understand trajectory(heavy VS light) in bullets.

My point was or is, if the riflings are clockwise or counter clockwise, if the riflings are clockwise and the closkwise spin causes the bullet to fall to the earth faster then say a barrel with riflings that were counter clockwise??? have there ever been any experiments with that???? because in my little simple twisted mind it almost makes sense that if a barrel that had clockwise riflings and with the clockwise spin of the bullet it would cause the bullet to fall back to the earth faster then a barrel with a counter clockwise riflings causing the bullet to spin counter clockwise?? also we would have to factor in the rotation of the earth. Welcome to my world, these are just questions I have.
Chuck
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: **HELP** Need to understand trajectory(heavy VS light) in bullets.
Thread Thread Starter Forum Replies Last Post
Heavy bullets vs.light bullets Crazycooydog Rifles, Bullets, Barrels & Ballistics 18 05-26-2012 12:25 PM
Opinions please ( heavy or light) rdsii64 Coyote Hunting - From 10 Yards to over 1,000 Yards 1 04-19-2011 02:01 AM
.243AI Light Versus Heavy Bullets? TORCHRIDER Reloading 9 12-06-2010 01:27 PM
Heavy vs. Light Bullets SES50 Reloading 9 06-29-2007 12:46 PM
Light vs Heavy bullets with similar BC's Len Backus Rifles, Bullets, Barrels & Ballistics 0 05-02-2001 10:38 PM


All times are GMT -5. The time now is 10:12 PM.


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