Bullet ballistics .

K

Kevin the grey

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Aug 26, 2005
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Woo hoo Friday , friday , friday !

I wish to discuss stable long distance bullet flight . How does a hollow point rate in this in both sub-sonic and above ? Does width and depth of hole matter ? Does it change because of bullet weight , length and diameter ? What about those pointed bullets with the approximately 30 mils hole ? I am also intrerested in boat tails .In fact that may be where I saw the small hollow point . In all cases I want to know if bullet length matters .

Spin : how does it come into play ? I understand it makes up for eccentricities . Is there anything beyond that ?

F:O:C: does it come into play with bullets ?
Drag . While drag affects more than the rear of the bullet are bullets designed to have slightly more drag at the rear ? Feel free to add relevant facts .

End result is not what you would expect . I am not shooting for accuracy . I am shooting for distance . In its own way it comes into play as innaccuracy will affect distance . I guess there has to be a comprimise .
 
Kevin the grey said:
Woo hoo Friday , friday , friday !

I wish to discuss stable long distance bullet flight . How does a hollow point rate in this in both sub-sonic and above ? Does width and depth of hole matter ? Does it change because of bullet weight , length and diameter ? What about those pointed bullets with the approximately 30 mils hole ? I am also intrerested in boat tails .In fact that may be where I saw the small hollow point . In all cases I want to know if bullet length matters .

Spin : how does it come into play ? I understand it makes up for eccentricities . Is there anything beyond that ?

F:O:C: does it come into play with bullets ?
Drag . While drag affects more than the rear of the bullet are bullets designed to have slightly more drag at the rear ? Feel free to add relevant facts .

End result is not what you would expect . I am not shooting for accuracy . I am shooting for distance . In its own way it comes into play as innaccuracy will affect distance . I guess there has to be a comprimise .
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There was an English general standing on the battlements of a castle with an enemy army approaching. His aids told him to take cover. He replied, and these were his last words, "They could'nt hit an elephant at this dist...."
 
Bill Marsh said:
There was an English general standing on the battlements of a castle with an enemy army approaching. His aids told him to take cover. He replied, and these were his last words, "They could'nt hit an elephant at this dist...."
Click to expand...

L:O:L Good one ! Just what I needed also . My birth week starts tomorrow and there is a whole lotta shakin going on . I lay down and feel a lot better . I,m gonna mega dose on the vitamin C and eat especially well today . I haven,t been ill in two years beyond a runny nose that went away in a couple of hours .
If I get the bird flu and sprout feathers will someone come and trim my wings for me ? Kukuuris only need apply .
 
cliff355 said:
Kevin:

This discussion may become long and complicated, but if you get confused there is more than most folks need to know about it in "Hatcher's Notebook" by Julian S. Hatcher.
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I do not mind complicated . As it is end result I am interested in and not theory I just need to know what works with a cursory explanation as to why .
I can also add the question if nodes of vibration come into effect within the bullet itsef ?
 
The Sierra reloading manual goes into ballistics quite a bit. You might consider getting one and using it as a resource.

Speer had a great essay called; "Why Ballisticians get grey hair" which was republished in one of their recent manuals.


munk
 
Please note that all other things (weight, concentricity,etc) being equal, a longer bullet has more sectional density...this actually translates into slightly better penetration, rather than distance. For better, flatter distance shooting, what you want is better ballistic coefficient, a function of shape being more areodynamic. All things are rarely the same though, so we get into trade offs. For instance, boat tail hollowpoints, a la Sierra et al, often have a little higher metal on one side drawn up around the hollow....so today's cutting edge bench rest shooters are now trimming hollowpoints a few thousandths to square off the hollow point so it won't wobble at long range. Another factor is keeping your bullet supersonic at longer range than that of your intended target. Bullets passing to below the speed of sound ?vibrate, ?wobble ? as they make the transition. This may account for the popularity of such barn burners as the .30/378 Weatherby in 20 pound rifles for over 1,000 yard shooting...trying to keep those long needle like projectiles supersonic way out there. There's more to this; this is of course an oversimplification. If I were to do a lot of extra long range shooting, I might build a 6.5/300 Weatherby instead of my beloved 270 Wea Mag ....those 140 grain 6.5 boattails boast very high ballistic coefficients, and lots less kick than 200 grain .300 Mag bullets.
 
I see I missed one of your key questions, how extra long, high ballistic coefficient bullets are affected by spin? Tight groups at long range require extra stabilization. Compounding the problem of finding how much spin is appropriate, muzzle velocity as well as bullet length are both variables, each dependent on the other. Several mathematical formulae exist, but they often give slightly different results. It's actually easier to ball park it, and arrive at a pretty good result. For example, you have been shooting a .223 with a 1 in 12 twist using 55 grain bullets and getting super tight groups, but 60 grain bullets from three different manufacturers just don't quite do as well. You read in a magazine that some are shooting 70 and 75 grain controlled expansion bullets for deer. Velocities for these heavier bullets will be lower in your rifle (using pressure safe loads) and therefore have a substantially slower spin, not enough for accuracy. If shooting these heavier bullets is really important to you, you're going to have to spring for a new barrel with a tighter twist, say 1 in 9" or even 1 in 8" and give up shooting the lighter bullets in that particular gun.

A .270 with a factory standard 1 in 10 twist will stabilize just about any bullet of that caliber on the market. A 7mm however, will handle 120's thru 150 grain bullets with 1 in 10" but usually work much better with 175 grain bullets in a 1 in 9" barrel often supplied by manufacturers, since most don't use light bullets in 7mm for varmints. Right now most of the extra long, high B.C. bullet experimentation is being done with .22 and 6.5mm calibers, and any good custom barrel maker can advise you if you furnish your caliber, which cartridge you plan to chamber for, and probable barrel length (longer barrels, slightly more velocity and spin). Despite our best intentions, one rifle for 'everything' doesn't work well. Great grounhog rifles do not make great deer rifles. Unless you plan on major experimentation with extra long bullets, most mid sized magnums (.25, .270 & 7mm) spin long bullets very well with standard 1 in 10" barrels if loaded near maximum and using 26" barrels. I chose to have fewer total rifles, and have a few great ones. I would urge you to consider a new or used Weatherby. The cost of shooting these usually means used Weatherbys have been shot little ( look for the lack of a ring around the firing pin hole on the bolt face). My experience with several has been super, and my sons are gradually carring them off in different directions, to my great satisfaction :D
 
Jurrasic, I agree with almost everything that you say, but would like to add a kicker. I have found that the faster twist barrels will shoot a lighter\shorter bullet pretty good (although not as well as a slower twist), where as a slow twist barrel plumb can't shoot a heavy and long bullet without being erratic or key holing.

I would second your thoughts on a 6.5mm cartridge, as the ballistic coefficient is just about as good as it gets.

Have fun, and be careful. If you plan on using a wildcat, be even more careful.

Stevo
 
Steveo, I doubt I'm ever going to cobble up that 6.5/300 Weatherby. I've been quietly fighting diabetic retinopathy, heart disease, and the ravages of cancer for years now. That's why I smile so much when my boys 'borrow' a rifle....they always leave alone the few I shoot most often....those will be theirs soon enough..;)
 
John Sedgwick fell to Confederate sniper fire at Spotsylvania Court House, 9 May 1864, after scolding his aids (who were ducking from the fire) that the enemy "Couldn't hit an elephant at this distance." This was probably a true statement, but they evidently could hit a Union Major General.

John
 
jurassicnarc, I'm sorry to hear about your health failing. My grandfather eyesight suffered the same fate as yours ~ pretty tough on anyone, 'specially hard on folks who are into precision shooting and such.

Smoke for my friend.

God Bless.
stevo
 
Right now I'm being lasered regularly, and my vision remains middlin', just not what it would take to be competitive waaay out there. These old eyes were good enough for a nice 7 point (eastern) this last November. The limiting factor really was my heart, and how far up and down hill I could get home in W.Va. God willing, I have a couple good years of teaching left. Thanks for the prayers.
 
These old eyes were good enough for a nice 7 point (eastern) this last November. The limiting factor really was my heart, and how far up and down hill I could get home in W.Va. God willing, I have a couple good years of teaching left. Thanks for the prayers.[/QUOTE]

Weird title for a post to a man who has health problems . I,m not downplaying them. I just appreciate that you are still out there enjoying yourself . A nice buck in the freezer ? Sounds good to me . Do you ever broil your venison over a campfire ? I have eaiten farm fed fork tender venison prepared by one of the finest chefs in the world . There is still something about a simple campfire meal . Don,t get me wrong . My personal cooking is lightly peppered or not at all a little olive oil and on a stick over the flame . It aint fancy but I just about slaver for it .
I,m wondering what your woods smell like ? I get the idea there is a lot of pine and other softwoods ? Lotsa pine needles under foot to soften an approach . It can make for a nice hunt .
 
I'm not sure what you're referring to when you say "weird title" for a guy with health problems. The ridges where I grew up in W.Va. are largely oak, hickory, maple and locust, as is the (rare) ridge I found in central Indiana. Cooking outdoors is something I used to do regularly, but seldom do anymore. Hell, I had to wait for my son to help me get the deer into the truck, something I used to do with ease a few years ago. I am older, and slower, but I still appreciate the hours afield, especially with my sons.
 
The title said "it sounds nice" and you were talking about your health problems . The nice part wasabout your hunt . Lotsa ridges eh ? Doesn,t that make for a lotta swirling winds ? I haven,t eaten outdoors except at a gathering or shoot in years . I better get at it and have a couplemore before I can,t . My brother-in-law is going on a boar hunt and I asked for the hides . Of course he said sure as long as I cleaned them myself . He gets the hog and I get the fat ! It doesn,t seem fair somehow ! L:O:L
I might wrangle a chop or two out of him and have myself a little cookout .
idon,t think its a biggie that your son has to help out . My Dad needs help sometimes and I just consider it a way to even things out a little . Thats one score that,ll never be even though . I guess thats how we become more .
 
I guess that one may over stabilize a bullet. That has not been my experiance.
If anything I find twists too loose.
 
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