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Is BC really that important @600 yds?

I have a 6br and I have found a few loads that work well in the 105-108gr range. I was looking at another page on this website that breaks down the bullets like popular 600 yard bullets are 80-90 grainers and 1000 yard bullets are 105-108s.

Since my 6br only shoots 600 yards should I be looking at some of the lighter bullets? Its a 1-8 twist so I just automaticly went for the,heavy for caliber) bullets with the highest BC.

Is lighter recoil and torque the main advantage to shooting the lighter bullets or is is something Im not thinking about? Does the advatage outweigh the BC factor @600?

Thanks
 
Some folks, like Bill Shehane, feel that the superior inherent accuracy of a flat-based match bullet trumps BC even out to 600 yards. You have to really run the numbers yourself.

In my 6BR, in ideal conditions at 100 yards, an 80gr Flatbase will shoot "high ones",0.18") while the 105gr Scenar will deliver "mid twos",0.25"). Extrapolating to 600 yards,assuming no wind effects, and perfectly uniform BCs) the "best" each bullet could do is:

80gr FBHP: 1.08" group
105gr BTHP: 1.50" group

FWIW I've shot a 1.6" group with the 105s at 600, so yes, it's "do-able."

Now, let's compare wind-drift at 600 yards. Assume I miss a 5 mph let-off. Here's how much the Point of Impact will change with each bullet:

80gr FBHP drift,3150 fps, .324 BC): 19.3"
105gr BTHP drift,2920 fps, .530 BC): 11.6"

So... I can improve maybe a half-inch in theoretical group size by going to the smaller, 80gr bullet, but then I can get "pushed" 66% further off target if I miss a 5 mph wind shift.

You can see how this favors the longer bullets.

For some folks, a 90-95gr boat-tail is a good compromise,between 80gr FB and 105gr BT). With a 90, you still have pretty decent BC and you can push the bullets faster. As I said, each shooter is going to have to work out the details himself and find which bullet works best in his rig.
 
Paul, if a shooter misses a 5 mph wind change..they're dead meat no matter what bullet they're using or yardage they're shooting. ;) -Al
 
That tells me everything I need to know. ;) Thanks alot for the detailed explanation, It keeps me from needing to ask follow up questions.:)
 
Al,
You maybe right, unless everyone missed the change. In that case, the guy who gets blown out the least is better off.

Furthermore, Paul's example applies for any level of wind. What if you miss a 0.5 mph change? The high BC bullet is moved 1.2", the low BC bullet is moved 1.9". This is still a greater advantage for the high BC bullet, even if the low BC,flat base) can group better in no wind:
80gr FBHP: 1.08" group
105gr BTHP: 1.50" group

BC is definitely a consideration at 600 yards. Not the only consideration, but is is important.

-Bryan
 
AlNyhus said:
Paul, if a shooter misses a 5 mph wind change..they're dead meat no matter what bullet they're using or yardage they're shooting. ;) -Al

Al,

Think of a 2.5 left going to a 2.5 right,or back and forth). At my range we have two mountain valleys that come together in a "T" at the target line. In the 600-yard matches the wind often switches back and forth at the top of the 'T' even if it seems steady at the firing line. I've seen many "good shooters" miss a Left to Right shift at the 600-yard mark. We don't allow personal flags past 50 meters, and there's just one flag at either end of the 600-yard line, placed about 30 yards away from the targets, so it is actually VERY easy to miss a switch. It can also blow left at one end of the target line and right at the other. Anyway, you get the idea.

At Sacramento I've seen a world record holder launch ALL 10 shots in a 1K relay off paper. And we all know the horror stories from Raton.

My range, looking down at 600. There's one flag on left end of distant berm, one at right:

Savage_2big.jpg


Hills on right side of "T"

Savage_LeftX640.jpg
 

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