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Joined: Sep 2001
Posts: 19,032
Campfire Ranger
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Campfire Ranger
Joined: Sep 2001
Posts: 19,032 |
Most of us post up to seek or share info/comraderie. Some post only really looking for a good ol' pissin' match.
I've 'gone there' a time or two, but it's not really my thing. Entertaining to read sometimes.
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Joined: Feb 2007
Posts: 1,538
Campfire Regular
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Campfire Regular
Joined: Feb 2007
Posts: 1,538 |
Not that I feel compelled to answer [bleep]'s post, but here is a picture of some 25 caliber bullets. The picture shows bullets that I have loaded for in .25-06. The two bullets to the far right were made by Wildcat Bullets. The second from right is 125g ULD and far right, 130g bonded bullet. As you can see with the bonded bullets, they are quite long. In my 1:10 twisted barrel, they didnt shoot well. Not sure if a coincidence or a twist issue. No keyholing though. So to answer your question, Wildcat Bullets did make a 130g bullet. With new ownership, not sure if they still are.
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Joined: Feb 2004
Posts: 46,745
Campfire 'Bwana
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Campfire 'Bwana
Joined: Feb 2004
Posts: 46,745 |
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]. and as we like to say in WI....WTF's a Buckeye.
Camp is where you make it.
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Joined: Feb 2009
Posts: 6,264
Campfire Tracker
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Campfire Tracker
Joined: Feb 2009
Posts: 6,264 |
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
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Joined: Jun 2009
Posts: 7,539
Campfire Outfitter
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Campfire Outfitter
Joined: Jun 2009
Posts: 7,539 |
If you need a 130 gr for a 25-06 just buy a 270
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Joined: Jun 2004
Posts: 44,805
Campfire 'Bwana
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Campfire 'Bwana
Joined: Jun 2004
Posts: 44,805 |
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.
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Joined: Feb 2009
Posts: 6,264
Campfire Tracker
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Campfire Tracker
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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
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Joined: Aug 2002
Posts: 7,445
Campfire Tracker
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Campfire Tracker
Joined: Aug 2002
Posts: 7,445 |
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.
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Joined: Sep 2009
Posts: 5,567
Campfire Tracker
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Campfire Tracker
Joined: Sep 2009
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At least he serve(d)........
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Joined: Apr 2004
Posts: 501
Campfire Regular
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Campfire Regular
Joined: Apr 2004
Posts: 501 |
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
Define your manhood not by success, but by significance. NRA Benefactor
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Joined: Jun 2004
Posts: 44,805
Campfire 'Bwana
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Campfire 'Bwana
Joined: Jun 2004
Posts: 44,805 |
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 .
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Joined: Jun 2004
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Campfire 'Bwana
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Campfire 'Bwana
Joined: Jun 2004
Posts: 44,805 |
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.
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Joined: Aug 2002
Posts: 2,583
Campfire Regular
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Campfire Regular
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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.
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Joined: Jan 2007
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Campfire Regular
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Campfire Regular
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Posts: 1,944 |
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
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Joined: Jun 2004
Posts: 44,805
Campfire 'Bwana
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Campfire 'Bwana
Joined: Jun 2004
Posts: 44,805 |
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.
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Joined: Apr 2004
Posts: 501
Campfire Regular
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Campfire Regular
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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. NRA Benefactor
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Campfire Regular
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Campfire Regular
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"volume = pi * r^2 * l"
What he said! I think??? Too many years since I used these equations.
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Joined: Mar 2005
Posts: 5,598
Campfire Tracker
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Campfire Tracker
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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. Bruce John Doe
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