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What TWIST RATE for which bullet weight |
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Dale Clifford ![]() Optics Jedi Knight ![]() Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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note -- one of the inputs is length |
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Dale Clifford ![]() Optics Jedi Knight ![]() Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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yes the military uses the smk for the long range load. the bc is still only around .4 so wind drift is still a factor, especially when the load is shooting below 3000 fps.
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scooter65 ![]() Optics Master Extraordinaire ![]() ![]() Joined: December/29/2006 Location: mi Status: Offline Points: 3567 |
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Great chart Wes... I was just looking for a cross reference chart like this and walla! I couldn't find the link online for it. I captured the chart image in a .jpg file if anybody would like it so they can just print the chart off. uploads/4389/twistrate.zipEdited by scooter65 - January/24/2010 at 12:46 |
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pyro6999 ![]() Optics Retard ![]() ![]() OT TITAN Joined: December/22/2006 Location: North Dakota Status: Offline Points: 22034 |
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lilja barrel company has a very nice chart as well, i have a copy of it printed out that i keep near my computer so when im looking at rifles and potential bullet combos in those rifles i can look at the twist rates and decide if its worth a shot or not.
http://www.riflebarrels.com/products/caliber_twist_rates.htm Edited by pyro6999 - January/24/2010 at 11:53 |
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They call me "Boots"
375H&H Mag: Yeah, it kills stuff "extra dead" 343 we will never forget God Bless Chris Ledoux "good ride cowboy" |
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scooter65 ![]() Optics Master Extraordinaire ![]() ![]() Joined: December/29/2006 Location: mi Status: Offline Points: 3567 |
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THANKS! Saved to my favorites list now.
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koshkin ![]() MODERATOR ![]() ![]() Dark Lord of Optics Joined: June/15/2004 Location: United States Status: Offline Points: 12339 |
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Berger Bullets website lists the recommended twist rate for every bullet they make.
ILya
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trigger29 ![]() Optics Master Extraordinaire ![]() ![]() X = 180 Y = 90 (X+Pyro)+(Y-Pyro) = ? Joined: September/29/2007 Location: South Dakota Status: Offline Points: 4348 |
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"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." |
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The Apostle ![]() Optics Journeyman ![]() ![]() Joined: August/20/2009 Location: Adelaide, S.A. Status: Offline Points: 409 |
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I'm going to get some bulk Federal Gold Medal Match in .308 Win...my Ruger is 1:10 twist...Which would suit my rifle best...168gr?...175gr?...or both???
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SVT_Tactical ![]() TEAM SWFA - Admin ![]() ![]() Chief Sackscratch Joined: December/17/2009 Location: NorthCackalacky Status: Offline Points: 30227 |
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Normally the faster twist will stablize a heavier bullet. I would try both to see which provided better accuracy, if they are equal then get teh 175. It will fight the wind better than the lighter grain. With a 10 twist you may even be able to put some bullets up to 200gr or even the 208 hornady a max. I know this doesn't really answer your question so if I had to say one of the two it would be the 175 because of wind drift
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Urimaginaryfrnd ![]() MODERATOR ![]() ![]() Resident Redneck Joined: June/20/2005 Location: Iowa Status: Offline Points: 14390 |
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"Always do the right thing, just because it is the right thing to do". Bobby Paul Doherty Texas Ranger |
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300S&W ![]() Optics God ![]() ![]() Joined: January/27/2008 Location: Burlington,WV Status: Offline Points: 10592 |
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Anyone familiar with this:
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"I ain't got time to bleed!"
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budperm ![]() Optics Retard ![]() ![]() show me your sheep!! Joined: January/01/2009 Location: Pennsylvania Status: Offline Points: 28802 |
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Interesting link Earl! I will have to save it and study it when I have more time!
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"Peace is that brief glorious moment in history when everybody stands around reloading".
--Thomas Jefferson |
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300S&W ![]() Optics God ![]() ![]() Joined: January/27/2008 Location: Burlington,WV Status: Offline Points: 10592 |
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Worked for me when I had to decide what rate of twist I wanted my 9.3 rebored to. Ended up at 1-12.
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"I ain't got time to bleed!"
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Bigdaddy0381 ![]() Optics God ![]() ![]() Georgia peach Joined: February/27/2007 Location: Georgia Status: Offline Points: 13329 |
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@50 yards this .243 with a 115gr berger it shot fine under1/2 group, now @100 the hit side ways. I'm not sure of the FPS on this load but as it slowed just a tad it started to flip. I guess most if it would depend on the bullet itself. as it might just have a yaw and not tumble. i want to say this is from a 1-10. I went with a 95gr for this rifle and it loves them out to 500 so far.
See they hit side ways.
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P&Z Firearms , Pro gun cleanings and gun repair and wood refinishing.
Ecclesiastes 10:2 |
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Dale Clifford ![]() Optics Jedi Knight ![]() Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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while the bullet decreases in speed, the rotational rate stays the same, so the amount of revolution per unit of distance traveled remains the same it takes more time to do it at the slowed velocity rate. Upon firing the base of the bullet is accelerated faster than parts of the bullet above this, (obtruation sp?). the more weight in the back causes better bc, but also gives more of shuttlecock effect. HBWC are an extreme example. At some point a bifurcation or change of a parameter in the relation between the inertial masses of the front and back and the tumbling occurs. Pitch and yaw are different.
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Bigdaddy0381 ![]() Optics God ![]() ![]() Georgia peach Joined: February/27/2007 Location: Georgia Status: Offline Points: 13329 |
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So a 1-10 twist stays 1-10 regaurdless of fps?
Dose obturation effect the flight of the bullet? Edited by Bigdaddy0381 - May/19/2010 at 08:16 |
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P&Z Firearms , Pro gun cleanings and gun repair and wood refinishing.
Ecclesiastes 10:2 |
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Dale Clifford ![]() Optics Jedi Knight ![]() Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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the spin rate doesn't slow down like the fps rate (more accurately -- the differential rate of change is considerably less, and the time or space constant can be ignored to linerize the problem). Obturation sets the conditions, if the bullet doesn't seal, gas blow by will tip the bullet on exit.
Especially true with cast bullets and alloy types. Yaw and pitch are oscillations or periodic sine waves that occur when position and time are plotted that occur. Bifurcation happens when the center of mass is moved thru the axis of the bullet and at some point the system falls apart and into an "attractor" of more stability.
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budperm ![]() Optics Retard ![]() ![]() show me your sheep!! Joined: January/01/2009 Location: Pennsylvania Status: Offline Points: 28802 |
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What did he just say?!?!? I think he is a closet lawyer.
I followed some of that but most went over at a rather high altitude.
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"Peace is that brief glorious moment in history when everybody stands around reloading".
--Thomas Jefferson |
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Dale Clifford ![]() Optics Jedi Knight ![]() Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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Numerical analysis can have different forms. When its used with ballistics as we talk about the calculations are done with numerical integrators using first order linear differential equations, that when plotted against each other, (the first matrix is time, the second is trajectory, etc, depending on the variable input) gives the plots and figures seen in places like JBM and Sierra. Usually a system (control systems) methodology isn't used because it gives other types of information, (such as the above) which doesn't really help someone hit something. A similar example is thinking of bullet energy (in terms of classical mechanics) as opposed to thermodynamics. Each give different information because the approach is different.
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Bigdaddy0381 ![]() Optics God ![]() ![]() Georgia peach Joined: February/27/2007 Location: Georgia Status: Offline Points: 13329 |
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[QUOTE=Dale Clifford]the spin rate doesn't slow down like the fps rate (more accurately -- the differential rate of change is considerably less, and the time or space constant can be ignored to linerize the problem). Obturation sets the conditions, if the bullet doesn't seal, gas blow by will tip the bullet on exit.
Especially true with cast bullets and alloy types. Yaw and pitch are oscillations or periodic sine waves that occur when position and time are plotted that occur. Bifurcation happens when the center of mass is moved thru the axis of the bullet and at some point the system falls apart and into an "attractor" of more stability. [/QUOTE]
Good point I didn't think of it that way. I was thinking more of the base of the bullet would go to one side or the other and not have a even base/contact. like 40% to 60% bottom would make the bullet wobble when it slows. Like out running a tire wabble on the high way. feel it slow and you don't when you speed up.
At what rate do you think or see it slowing too? If I can find the email from a controled test I'll post it. from the test it showed the rotation slowed as the velocity slowed and the twist stayed the same. Let me do some digging..
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P&Z Firearms , Pro gun cleanings and gun repair and wood refinishing.
Ecclesiastes 10:2 |
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Dale Clifford ![]() Optics Jedi Knight ![]() Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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ask the question from a different view-- what drag forces are acting on the rotational spin?
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pyro6999 ![]() Optics Retard ![]() ![]() OT TITAN Joined: December/22/2006 Location: North Dakota Status: Offline Points: 22034 |
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They call me "Boots"
375H&H Mag: Yeah, it kills stuff "extra dead" 343 we will never forget God Bless Chris Ledoux "good ride cowboy" |
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trigger29 ![]() Optics Master Extraordinaire ![]() ![]() X = 180 Y = 90 (X+Pyro)+(Y-Pyro) = ? Joined: September/29/2007 Location: South Dakota Status: Offline Points: 4348 |
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It seems to me that if a bullet is stabilized when it leaves the barrel, it should stay that way as long as no outside force interrupts it. The bullet's velocity will bleed off fairly fast, where as the rotational force should not lose it's speed nearly as fast...........Or I'm way off base, and as usual don't know what I'm talking about.
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"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." |
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Bigdaddy0381 ![]() Optics God ![]() ![]() Georgia peach Joined: February/27/2007 Location: Georgia Status: Offline Points: 13329 |
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The twist has to slow some. The ojive has a bearing surface that has an extreme force pushed upon it. I agree it will not slow as fast as the velocity but it slow to where the twist rate stays the same. If it didn't the twist rate would speed up. Say a 1-10 at 3,000 fps @ 20yards and a 1-5 at 1,500 @ 800yards if the twist didn't slow when shot from the same rifle. It’s easier to say than type. Edited by Bigdaddy0381 - May/20/2010 at 08:26 |
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P&Z Firearms , Pro gun cleanings and gun repair and wood refinishing.
Ecclesiastes 10:2 |
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cyborg ![]() Optics God ![]() ![]() Gaseous Clay Joined: August/24/2007 Location: North Georgia Status: Offline Points: 12253 |
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Air has a mass, and as such forces friction upon things moving whether they are spinning or moving in a path. That affect is a constant. The bullet will lose spin at a proportional rate that it loses forward movement so long as it remains in flight..
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