|
Author
|
Topic: Bullet Design ??
|
Kokopelli
SENIOR DISCOUNT & Dispenser of Sage Advice
Member # 633
|
posted April 18, 2005 02:42 AM
If this question doesn't seem to make any sense, please bear with me; I know a heck of a lot more about 'pointed sticks with feathers' than I do about this 'bang-flopper' I've been useing.
As an archer, I know that the bow must be tuned to the proper stiffness arrow and that the arrow must be tuned to have a forward of center balance point, aprox. 6 to 11 percent, for correct flight. A simple example would be throwing a sappling for a spear. The heavy end is the point. Doesn't work any other way.
Now we come to bullet design.
With the exception of the old Foster shotgun slugs, bullets have a rear center of balance. Even more so with hollow points.This doesn't seem 'right'.
Also, while we're on the subject; the base of bullets, even boat-tails, are pretty much flat. I may not know squat about 'ballistic coefficients' but I do know that a regular canoe is a lot easier to paddle than a square sterned one. Something about drag.
Therefore?? It would seem that a bullet (for accuracy only) should be shaped somewhat like a football with parallel sides for the rifleing, having lead in the front and something light like tin in the rear, with a copper jacket enclosing the whole. Sleek and areodynamic.
Where am I going wrong here??
--------------------
And lo, the Light of the Trump shown upon the Darkness and the Darkness could not comprehend it.
Posts: 8231 | From: Under a wandering star | Registered: Apr 2005
| IP: Logged
|
|
Tim Behle
Administrator MacNeal Sector
Member # 209
|
posted April 18, 2005 06:15 AM
Thing about it in terms of speed. When the bullet leave the barrel, it is going much faster than an arrow, spear, football or canoe. It's going faster than the speed of sound.
A bullet has gyroscopic ability imposed on it by the centrifugal force gained by passing through the rifling in the barrel.
Boat tailed bullets aren't needed for accuracy until out in the 600 yard range in most rifles. By then, the forward speed of the bullet has slowed, but the RPM of the bullet, having less drag , hasn't slowed. The boat tail causes less drag at the base, and helps the bullet to stay more accurate at longer ranges.
--------------------
Personally, I carry a gun because I'm too young to die and too old to take
an ass kickin'.
Posts: 3160 | From: Five Miles East of Vic, AZ | Registered: Jun 2003
| IP: Logged
|
|
Leonard
HMFIC
Member # 2
|
posted April 18, 2005 10:42 AM
Yeah, it would help to think of the bullet in flight as a gyroscope, then you don't have to consider all the weight forward stuff, as with an arrow.
The flat base is essential, for accuracy. Having the gasses bear on anything that is not perfectly perpandicular to the rifling direction results in erratic flight similiar to a damaged crown. Understand, a boat tail bullet still needs a flat base.
Other than that, consider your concept from a mechanical point of view. Assuming that you know how jacketed bullets are manufactured?
Good hunting. LB
--------------------
EL BEE Knows It All and Done It All.
Don't piss me off!
Posts: 32361 | From: Upland, CA | Registered: Jan 2003
| IP: Logged
|
|
Weedwacker
Knows what it's all about
Member # 329
|
posted April 18, 2005 06:27 PM
Rifle bullets do however conform somewhat to your thinking in a medium more dense than air losing the gyroscopic effect. They tend to yaw in a dense medium going heavy- end-forward if they are not designed to expand ie. full metal jacket. This makes the terminal performance less predictable. Part of the beauty of an expanding bullet is as it penetrates it goes weight forward quickly becoming arrow-like and precluding a yaw, giving a more predictable path and performance. The tendency to yaw in a dense medium can vary but in general seems to drop off greatly after 200 yards. I've heard that explained as the bullet becoming more stable near that point in the flight, apparently losing whatever minute wobble it left the barrel with. Seems to make sense it would not be as likely to yaw if it entered perfectly strait.
I bet if we fired a long conical bullet down a barrel with no rifling your thoughts would all apply and it would tumble.
That's it! The archery world needs a gizmo to put massive spin on the arrow! Something like a long corkscrew thingy like those automatic screwdrivers you push in on and they spin. Or just have a little bearing set to allow your knock point to spin and push it through a little rifled barrel you mount on your overdraw. You can throw away your fletchings! Of course your arrow will get grooved so you will need to buy a new arrow for each shot ![[Frown]](frown.gif)
--------------------
Weedwacker
http://pub119.ezboard.com/bindianapredatorcentral
Posts: 34 | From: Angola, IN USA | Registered: Mar 2004
| IP: Logged
|
|
Rich Higgins
unknown comic
|
posted April 18, 2005 07:13 PM
The purpose of off-set or spiral arrow fletching is to impart a spin to stabilize the flight of the shaft. Spine and balance aren't nearly as critical. Arrows for my heavy longbows are spiral flethed. Arrows for my compound are fletched straight.
IP: Logged
|
|
DAA
Utah/Promoted WESTERN REGIONAL Hunt Director
Member # 11
|
posted April 19, 2005 06:06 AM
The spin is really only important when you have another rudder out front though (broadhead). With a bullet or field point, a perfectly tuned bow shoots very well without any fletching.
And even spine is only important with older designs of bow and arrow rest. With a new centershot bow and a fall away rest, spine doesn't even seem to matter, much. As long as it's tuned for centershot and timing.
Even FOC seems shaky, these days. A lot of tournament wins have been booked with setups running crazy FOC, way outside what's always been considered "required".
- DAA
--------------------
"Oh yeah, they're gonna talk to you, and talk to you, and talk to you about individual freedom, but they see a free individual, it's gonna scare 'em." -- George Hanson, Easy Rider, 1969.
Rocky Mountain Varmint Hunter
Posts: 2676 | From: Salt Lake City, UT | Registered: Jan 2003
| IP: Logged
|
|
Melvin
Knows what it's all about
Member # 634
|
posted April 19, 2005 04:50 PM
Like a spear...It has no fletching
Posts: 661 | From: PA. | Registered: Apr 2005
| IP: Logged
|
|
Kokopelli
SENIOR DISCOUNT & Dispenser of Sage Advice
Member # 633
|
posted April 22, 2005 02:21 AM
Thank you guys for the replies. Speed & spin seem to make sense. I don't get carried away with this accuracy thing; 1/2 minute of coyote is good. Anywhere thru the lungs and "Dog-gone, him take dirt nap". Just something I wonder about when I have to much time on my hands.
Rich; Some time spent shooting broadheads thru a paper tuner at 60 yards in a cross or quartering wind may change your mind about straight fletch.
Weedwacker; Archery does not need any more 'gizmos'!!! What works well on the feild or 3D course is not always the answer when hunting. Simple is good.
--------------------
And lo, the Light of the Trump shown upon the Darkness and the Darkness could not comprehend it.
Posts: 8231 | From: Under a wandering star | Registered: Apr 2005
| IP: Logged
|
|
|
UBBFriend: Email this page to someone!
Printer-friendly view of this topic
