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Need some rifle twist experts to help me out...

 
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  #36  
Old 01-06-2014, 02:02 AM
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Re: Need some rifle twist experts to help me out...

The problem comes when dimensions become marginal. To illustrate what I have encountered it is probably best to use an actual example. A reloader has a new Sako 300 Win Mag. All new Sako and Tikka rifles in .30 caliber have 11" twist hammer forged barrels.

He wanted to use our 177gr HV for plains game and our 180gr FN for the small 5 to save cape damage and in case he walks into a cape buffalo.

The Miller method gave the Sg of the 177gr HV as 1.12 and the 180gr FN as 2.19 and both are numbers in line with what he wants. The minimum required for an HV is Sg 1.1 and for an FN it is over Sg 2.0.

McCoy, on the other hand gives the 177gr HV as Sg 0.95 and the 180gr FN as 1.24. Both fall far short of what is required.

When he started working up his load, the 177gr HV was sideways on a 25 m target. Fortunately he did not try the 180gr FN. The 180gr FN will give stable flight but fail to penetrate in a stable manner giving massive meat damage and unreliable penetration.

We changed him (with great difficulty) to a 150gr HV at Sg 1.4 and a 145gr FN at Sg 2.8 and he is hunting with exactly the results he wants.

Every user is free to experiment and spend his money as he wishes. The problem starts when a user is not as knowledgeable as Michael and does not understand why he is getting a result he did not expect. He then perceives his actions as a waste of his money and time and blames the product, thinking that he has acted correctly. We try to avoid that.
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  #37  
Old 01-06-2014, 02:31 AM
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Re: Need some rifle twist experts to help me out...

Quote:
Originally Posted by Gerard Schultz View Post
The problem comes when dimensions become marginal.
Very true. 11x barrels are not always exactly 11x. Or any other twist.

Gerard, it is obvious that you guys get quite technical in your business. It's good to see and we appreciate it.

M
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