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7mm 180gr SMK

 
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  #1  
Old 07-31-2013, 06:58 PM
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7mm 180gr SMK



The 7mm 180 grain HPBT MatchKing was created in response to requests from top-level F-Class shooters. Sierra has designed these MatchKing to provide a higher weight/higher B.C. alternative in our 7mm line. This bullet's 12 caliber secant ogive and lengthened boat tail make it the perfect choice for the discerning 7mm long range shooter.



Please Note!! This bullet requires at least a 1x8" twist barrel.

my rifle on order has a 1-9 twist brux

has anybody tried these in a 1-9?
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  #2  
Old 07-31-2013, 08:30 PM
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Re: 7mm 180gr SMK

Quote:
Originally Posted by cummin_un_glued View Post
has anybody tried these in a 1-9?

The required twist rate for a given bullet is a function of several things. Most important are the air density and the bullet muzzle velocity . At supersonic velocities most bullets are more stable the faster they are driven. The force of air trying to upset the bullet is higher but the spin rate is faster and is a little more important.

Cold dry high barometric pressure air is denser than warm moist low barometric air. Denser air requires a faster twist rate. A 9 inch twist barrel with a 280 or higher velocity cartridge shoots 180 SMK and Bergers just fine at the mile plus altitude in Arizona where I shoot most of the time. At that altitude even sub freezing temperature is not a problem. At lower elevation and colder temperatures I can't say.

The best way to find out if a given bullet will be stable in your rifle in the conditions you'll be shooting is to shoot some long range targets for group size in conditions with a little higher air density than you expect to hunt in. Asking on the Internet if they shoot OK or using computer stability simulators like McGyro is is far less reliable.
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  #3  
Old 08-01-2013, 09:03 PM
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Re: 7mm 180gr SMK

Quote:
Originally Posted by LouBoyd View Post
The required twist rate for a given bullet is a function of several things. Most important are the air density and the bullet muzzle velocity . At supersonic velocities most bullets are more stable the faster they are driven. The force of air trying to upset the bullet is higher but the spin rate is faster and is a little more important.

Cold dry high barometric pressure air is denser than warm moist low barometric air. Denser air requires a faster twist rate. A 9 inch twist barrel with a 280 or higher velocity cartridge shoots 180 SMK and Bergers just fine at the mile plus altitude in Arizona where I shoot most of the time. At that altitude even sub freezing temperature is not a problem. At lower elevation and colder temperatures I can't say.

The best way to find out if a given bullet will be stable in your rifle in the conditions you'll be shooting is to shoot some long range targets for group size in conditions with a little higher air density than you expect to hunt in. Asking on the Internet if they shoot OK or using computer stability simulators like McGyro is is far less reliable.
I understand all of that. I was looking for first hand experiences. Plenty of guys on here that shoot the 7mm's of various kinds so I figured at least a few have tried it and could save me the trouble. the gun is being chambered in 7mmx300win so it will be plenty fast. I guess I will just load some up and try it when it gets here. i'm at 500ft and I hunt at 7500ft so if it shoots good here it should shoot even better in WY.
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  #4  
Old 08-01-2013, 10:39 PM
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Re: 7mm 180gr SMK

I have a 9 twist and a 8 twist in 284 win. There both 28 inches long. I can't tell the difference out to 1200 yards shooting the SMKs.
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  #5  
Old 08-02-2013, 02:50 PM
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Re: 7mm 180gr SMK

Quote:
Originally Posted by APEX View Post
I have a 9 twist and a 8 twist in 284 win. There both 28 inches long. I can't tell the difference out to 1200 yards shooting the SMKs.
thank you sir
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  #6  
Old 08-04-2013, 09:52 PM
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Re: 7mm 180gr SMK

Quote:
Originally Posted by cummin_un_glued View Post
thank you sir
Sorry! Hit the wrong button, with the quote! I too have a 7/300 being built now! I even had my reamer made for the 180 SMK's! After everything I read in the other thread concering the 7/300, I really don't think you'll have any problem! I own three 7mm an only one of them really doesn't like the 180's, the other two shoots them pretty good. Just my 2cts!!

DT
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  #7  
Old 08-04-2013, 09:55 PM
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Re: 7mm 180gr SMK

The 7/300 I'm building has a 28in keriger1n9 twist!

DT
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