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What TWIST RATE for which bullet weight |
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Urimaginaryfrnd
MODERATOR Resident Redneck Joined: June/20/2005 Location: Iowa Status: Offline Points: 14962 |
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http://le.atk.com/pdf/223_MinimumTwistRates.pdf Your best performance will be with bullets no longer than .829 inch with a 1:9 twist. The 69 gr bullet is .900 I would suggest you measure the length of the 60 gr AMAX Horniday and try that fot the 1:9 twist.
You can shoot the 77 but it may not be as tight as it would with something in the 55 to 60 grain weight. Try it and see what you get. Note some 75 and heavier bullets have to be single shot loaded especially the 80 gr.
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RONK
Optics Master Extraordinaire Joined: April/05/2007 Location: United States Status: Offline Points: 3199 |
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Could go either way.
Shoot them to find out. It's the only way to know.
You're on the borderline though, in my estimation.
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koshkin
MODERATOR Dark Lord of Optics Joined: June/15/2004 Location: United States Status: Offline Points: 13181 |
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77gr is a little heavy for 1 in 9 twist. It might work well, but chances are you will do better with a lighter bullet. My 1 in 9 twist 223 seems to really like 69gr SMKs. ILya
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GetSome
Optics Journeyman Joined: December/12/2009 Location: Oregon Status: Offline Points: 516 |
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I would like to try some 77 gr. in my .223 1in8...does the military use sierra? And I would assume it would have to have a cannalure, so is that set back far enough to allow a crimp and still feed through a mag without single loading...I would imagine it would have to. Any info you have would help I don't know anyone I could ask about the 77s locally.
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koshkin
MODERATOR Dark Lord of Optics Joined: June/15/2004 Location: United States Status: Offline Points: 13181 |
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I am pretty sure there are two varieties of 77gr SMKs: with cannelure and without it. I have only used the ones without cannelure, so I can't comment on the other ones. ILya
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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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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: 13181 |
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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: 4353 |
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The Apostle
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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
MODERATOR Chief Sackscratch Joined: December/17/2009 Location: NorthCackalacky Status: Offline Points: 31233 |
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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: 14962 |
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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: 31710 |
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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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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
MODERATOR Georgia peach Joined: February/27/2007 Location: Georgia Status: Offline Points: 13680 |
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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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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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