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168gr LRX stability in 7mm WSM

 
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  #1  
Old 01-30-2013, 11:36 AM
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Join Date: Jan 2013
Location: Maple Valley, Washington
Posts: 457
168gr LRX stability in 7mm WSM

I was working up loads for my 1 in 9 twist 7mm WSM using the 168 grain Barnes LRX when I noticed that the carbon smears from bullets passing through the paper tended to be elongated and that one bullet hole looked like two. When I got the velocity up to 3,080 fps, I finally got my first round bullet hole. So I pulled up Berger’s twist rate tool and punched in the data for the bullet and sure enough it calculated and SG of 1.23. Less than 1.4 shows “marginal stability” and at less than 1.0 the bullet will be tumbling.

Worse yet, the calculator assumes that the bullet has a lead core which it doesn’t. Since it isn’t tumbling I know the SG is somewhere between 1.00 and 1.23.

I ended up with a velocity of 3,157 fps which added 0.01 to the SG for a grand total of something less than 1.24. Here is the interesting part. Even though some of the bullet holes are elongated, it still put 5 shots inside 1.6 inches at 200 yards – this all at 750 feet elevation and 39 degrees F. I’ll be hunting at 4,000 feet or higher where the SG jumps up by 0.15 to something less than 1.39. Anyway, I’m thinking I can use these LRXs in my 1 in 9 twist but just barely.

Question: Is this a dumb idea to be thinking I can take these hunting?
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Old 01-30-2013, 04:58 PM
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Join Date: Sep 2011
Location: West Wendover, NV
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Re: 168gr LRX stability in 7mm WSM

Here's what I got from Ty Herring at Barnes....
We are recommending the 175gr TSX load data for use with the 168gr LRX. Also be sure you have the correct barrel twist as most factory 1 in 9.25” to 9.5” barrels will not stabilize this bullet. We are recommending the 1 in 9 twist for those at higher altitudes (5000ft and above) and those at sea level up to 5000ft will require a 1 in 8 twist barrel to stabilize it.

Now I have a Remington Sendero with a 9 1/4 twist in a 7mmSTW, and I live at about 4200ft elevation, and they stabilize just fine for me at 100 yds. I have shot them out to 663 yards with no problems. Maybe the elevation is screwing you up?
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Old 01-31-2013, 12:03 AM
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Join Date: Jan 2013
Location: Maple Valley, Washington
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Re: 168gr LRX stability in 7mm WSM

Black Sheep

That clears up a few things. Very good info. Just what I needed. Thanks. I’m going to use them as they shoot pretty good at 750 feet and will only improve with altitude.
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