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Old 07-26-2009, 6:55 PM
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Slash2 Slash2 is offline
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Originally Posted by L8Apex619 View Post
IIRC, the data published by Sierra was based on a 26" barrel (for .308). That should equate to a loss of just under 150 FPS out of a 20" barrel:

Using their load data, it looks like it would take an extra 2.4 grains of BLC-2 to make up that difference... which should put you right around 47.6 grains - almost a full grain under Sierra's published max load. How much BLC2 are you loading?

ETA: How far (from your rifle) is your chrono?

At Sierra's max load for BLC(2) of 48.4 I was hitting 2650 fps with the chronny at 10 ft from the muzzle, 250 fps below their data. I went up to 49 grs, hit about 2700 fps, but started getting pressure signs so I stopped. However I was seating the bullet to my max magazine length of 2.835" to minimize the jump, that probably accounts for the lower velocity.

Since I've gone back to the published OALs, which actually has improved my groups, but I haven't chrony'd those loads yet, I'm guessing the fps is probably closer to the 150 fps below mark now.
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