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ballistic coefficients?

 
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  #1  
Old 07-16-2003, 12:08 PM
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Join Date: Jul 2002
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ballistic coefficients?

i was just reading up on some long range shooting and i came across this bit of info that i found hard to believe. i noticed that nosler lists the 7mm 140gr ballistic tip with a bc of .485, while sierra's 168MK has a bc of .488. my ? is this. i can shoot the 140gr at about 3250-3300 fps. i can only shoot the MK to about 3000 fps. so if my calculations are correct, the ballistic tip would be the best bullet out to 700 yds? i never thought to check, but just by looking at the bullet, the sierra looks like a much better bullet, but i would just like yall's opinion on this matter. thanks

cdixon
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  #2  
Old 07-16-2003, 12:26 PM
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Re: ballistic coefficients?

Cdixon

The BC of the 168 Sierra MK is .636

Even if you ran the 168 gr Much slower (say 3000 to 3100 fps) then the 140 gr, the 168 would most certainly shoot flatter at "longrange".
If you really want to reach out with the 7mm, try the 180 gr creations.

I can run the drops if you wish.

The 140 gr has a .488 BC which really is not that good for a 7mm bullet.

I like to start with a bullet that has at least a .555 BC and above in any of the Longrange rifles I use.

Then again, the range one shoots makes a difference too.

If your shooting out to 500 or 600 yards it really may not make a big difference to you. After that yardage it's the higher BC and normally heavier bullets that will win out even if it is going slower to start with.

Later
DC

As an add on---Here are the numbers concerning the two bullets.

140gr Going at 3250 FPS Starting velocity has remaining Velocity of 2037 FPS and 1290 Foot Pounds of energy left at 700 yards.

The 168 gr going at 3050 FPS out the barrel has remaining velocity of 2129 Feet per second and "1691 foot pounds" of energy left at 700 yards.

At 700 yards the velocity is faster and the energy level is higher with the 168 gr.

[ 07-16-2003: Message edited by: Darryl Cassel ]
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  #3  
Old 07-16-2003, 12:37 PM
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Re: ballistic coefficients?

thanks alot darryl. sierra's site has them listed at .49. i thought that sounded low. what are the 180gr creations? again thanks alot. you have been a great help to me in developing my long range load.

cdixon

ps, darryl if you dont mind could you run the drop charts for my rifle with the 168Mk at about 3050 fps? i tried the ballistics calculator at realguns.com, but it also lists the wrong bc for that bullet. do you know of any online ballistic calculators? thanks a bunch

[ 07-16-2003: Message edited by: cdixon ]
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Old 07-16-2003, 12:43 PM
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Re: ballistic coefficients?

Check my last post.

I just ran the numbers for you using the 3050 FPS velocity for the 168 gr.

Later
DC
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  #5  
Old 07-16-2003, 12:43 PM
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Location: Nanty-Glo, Pennsylvania
Posts: 127
Re: ballistic coefficients?

Darryl

i believe the BC of the 168 Sierra MK in 7mm os only .488. Remember Sierra had it listed higher years ago, then moved to Missouri from the Republic of Kalifornia and listed it at .488 stating that they had chronograph trouble or something in the past.

---Dan
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  #6  
Old 07-16-2003, 12:48 PM
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Re: ballistic coefficients?

Hello Dan

It is listed at .636 from Oehler Ballistics.

The 168 seems to fly true to these BCs from my 7/300 Weatherby as per drops at various ranges?

I'm running the 168 gr from the 30" barrel at
3200 to 3250 Fps depending on the load.

Later
DC
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Old 07-16-2003, 04:35 PM
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Re: ballistic coefficients?

Darryl

Dont want to but in, but if the Sierra 168g SMK has a BC of .636 than what would be the BC of the 200g SMK? Sierra list it at .565. I would be interested in knowing what you have discovered it to be or Oehler. I have seen on this site many times where the Sierra SMK's tend to have a slightly higher BC than what the Sierra Manual lists, but I didn't think it was that much. I am interested in the 200g SMK for my sendaro in .300 Win at ranges to 600 yards. Hoping it will be over .600? Thanks.
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