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#3873157 - 03/08/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: Steelhead]  
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tzone Offline
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Originally Posted by Steelhead
Originally Posted by BuckeyeSpecial
Mr. Montana Marine et al:

Read the original post, a 130 grain bullet in 25 caliber; I will now qualify it as a 130 grain "hunting" bullet and not a VLD.

Not trying to be a smart guy, just trying to gain an answer with my preferred level of credibility.... looks like you guys don't 'really" know.

Despite your illustrious artillery experience, I see no formula, nor a reference to a ballistics engineering degree (perhaps you have one) So, I guess I will call Sierra someday....


Unfortunately I don't share Shane's coolness, so you can shove a 130 bullet right up your ass [bleep].


grin

and as we like to say in WI....WTF's a Buckeye.

CMG 300 BP

#3873254 - 03/08/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: tzone]  
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exbiologist Offline
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The one thing that hasn't been mentioned so far regarding twist, and why slower twists work better in larger calibers is because twist affects the surface speed. If you spin a .35 caliber bullet in a 1:10 at the same velocity as a .25 caliber through a 1:10, the outside diameter of the .35 will be spinning much faster than the .25 The center of the bullet will be spinning at the same rpm, but not the outside of the bullet.
So that's why it takes such a fast twist in .22 calibers to stabilize bullets with a lower sectional density, length, or BC than a .25 cal of the same weight.
Make sense?
And, no I'm not a ballistic engineer. If I was, then the term for "outside diameter speed" would have come to me, but it didn't.


"For some unfortunates, poisoned by city sidewalks ... the horn of the hunter never winds at all" Robert Ruark, The Horn of the Hunter

#3873267 - 03/08/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: BuckeyeSpecial]  
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savage62 Offline
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If you need a 130 gr for a 25-06 just buy a 270

#3873289 - 03/08/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: exbiologist]  
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mathman Offline
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Quote
The center of the bullet will be spinning at the same rpm, but not the outside of the bullet.


You are mixing angular and linear quantities here.

#3873317 - 03/08/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: mathman]  
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exbiologist Offline
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I know, help me out with the terminology. But the idea is correct right? Larger diameter bullets need less twist than little bullets, which is why a .22 needs a 1:7 for long match bullets and .26 needs a 1:8 for even longer match bullets, and a .338 does fine with a 1:10 with 300 grain match bullets.
Right?


"For some unfortunates, poisoned by city sidewalks ... the horn of the hunter never winds at all" Robert Ruark, The Horn of the Hunter

Alpha

#3873483 - 03/08/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: Steelhead]  
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FVA Offline
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Originally Posted by Steelhead
Originally Posted by BuckeyeSpecial
Mr. Montana Marine et al:

Read the original post, a 130 grain bullet in 25 caliber; I will now qualify it as a 130 grain "hunting" bullet and not a VLD.

Not trying to be a smart guy, just trying to gain an answer with my preferred level of credibility.... looks like you guys don't 'really" know.

Despite your illustrious artillery experience, I see no formula, nor a reference to a ballistics engineering degree (perhaps you have one) So, I guess I will call Sierra someday....


Unfortunately I don't share Shane's coolness, so you can shove a 130 bullet right up your ass [bleep].


Sums it up quite well. Guy deserves a in person, back of the neck held, face in the dirt.....held long.


#3873510 - 03/08/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: BuckeyeSpecial]  
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oldman1942 Offline
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At least he serve(d)........

#3876637 - 03/09/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: oldman1942]  
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Fast_Ed Offline
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angular velocity

Outside of a larger diameter bullet has farther to travel to get all the way around. Since the rotational velocity is the same given the same twist and the same linear velocity, the larger diameter bullet has a higher angular velocity.

What I don't know is what that has to do with stability.

Fast Ed


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#3877009 - 03/09/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: Fast_Ed]  
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mathman Offline
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Since the rotational velocity is the same given the same twist and the same linear velocity, the larger diameter bullet has a higher angular velocity.


No. Angular velocity is the measure of the speed of rotation about the axis.

At the same angular (rotational) velocity a larger diameter bullet has a higher surface speed .

#3877034 - 03/09/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: exbiologist]  
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mathman Offline
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Larger diameter bullets need less twist than little bullets,


Larger diameter bullets have higher axial moments of inertia which contributes to their stability, lessening the required twist.

Bravo

#3880265 - 03/10/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: BuckeyeSpecial]  
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natman Offline
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Originally Posted by BuckeyeSpecial
Gee, replies so far are interesting but a little short on a some engineering references...

As in, how do all the [heavier] 6.5, 7mm, 30 and even larger caliber bullets work in a 1x10 twist? Can you cite a controlling formula...?

An engineer, is there an engineer in the house?


Do a google search on "greenhill formula".

The twist rate depends on the length of the bullet, not its weight. You can shoot 130 grain+ bullets with a 1:10 twist in larger calibers because since the bullet is larger in diameter, it doesn't have to be as long for a given weight.


#3880466 - 03/10/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: natman]  
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x2mosg Offline
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To add to what natman said, an increase in diameter does not increase the volumn in a linear pattern. So the weight/length ratio changes as the diameter increases. As bullets get larger in diameter, the length of bullet to gain, say, 10gr., actually decreases. EX: hypothectically let's say a 7mm(.284") bullet takes a length increase of .005". A .458" bullet may only take .001" to increase 10gr. in weight. But the change is not linear. You can't say it takes "X" increase in length per "Y" change in diameter. Hope that makes sense. Circles don't work like squares, basically.

David

#3880496 - 03/10/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: x2mosg]  
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mathman Offline
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For the cylindrical part of the bullet it's easy. For a cylinder of radius r and length l we have

volume = pi * r^2 * l

So volume, hence mass, grows linearly with length and quadratically with radius.

#3880854 - 03/10/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: mathman]  
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Fast_Ed Offline
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Quote
No. Angular velocity is the measure of the speed of rotation about the axis.

At the same angular (rotational) velocity a larger diameter bullet has a higher surface speed .


I stand corrected. Been a lot of years since my college physics days.

Fast Ed


Define your manhood not by success, but by significance.
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#3881091 - 03/10/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: Fast_Ed]  
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x2mosg Offline
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"volume = pi * r^2 * l"

What he said! I think??? Too many years since I used these equations.

#3881195 - 03/10/10 Re: Why No 130 Grain Bullet For The 25/06 [Re: x2mosg]  
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bcp Offline
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If you want to shoot 130-140 grain bullets in your 25-06, just take the rifle in to your gunsmith and have him put his barrel wrench on the muzzle and give it an extra turn to tighten the twist.

wink

Bruce John Doe

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