Energy and Velocity Question

NatureNick said:

I'd avoid ShootersCalculator.com; their formulae use the BC as a constant, it seems, rather than properly treating it as an average within the specified range of velocity and assigning increasing/decreasing BC as appropriate along the affected section of the calculated parabola. Applied Ballistics' calculator (http://appliedballisticsllc.com/ballistics/) has been a lot more accurate for me on everything from .22-250 through .470NE, with stops between those two diameters mostly in the .264-.308" range. I've only used it with 2 different saboted muzzleloading bullets but it got me close enough to get my 100 yard zeroed load on paper (8.5x11" sheets) at 200 and 300 yards with 250 and 300 grain saboted bullets.

The other reason I recommend Applied Ballistics' calculator is that it will use the variables such as wind (not just the speed you input, but the most likely range of wind speed/value variations' cumulative effects at the input distance), shooter confidence, etc., to paint a "Weapon Employment Zone," or the scatter effect over a substantive sample quantity of shots and its resultant probability of hitting a target of a specified size at that distance.

In the case of your .241 BC, 290 grain .451" dia. bullet at 1,960 fps, even if you have perfectly solid shooting form, estimate your wind within +/- 2.5 mph of actual conditions at all distances, estimate range to within 40 feet, and shoot to the full potential of a rifle consistently capable of 1 MOA with no more than 15 fps standard deviation, your probability of a first round hit anywhere on a standard 30x18" IPSC/IDPA target at 500 yards is still no better than 28%. I don't have my good laptop handy tonight or I'd scale that to a 10 shot sample size at 200, 250, and 300 yards for you. (I just used the free version at the link I gave, which doesn't allow changing those parameters of distance and sample size. My laptop with the $200 program installed is with my wife this weekend at a sewing retreat since her iPad won't control her embroidery machine.) More realistic variables are probably 1.5 to 2 MOA, SD=30~50, and I leave it to you to grade your own shooter confidence. What's more, both your and my velocity curves show your bullet going transonic somewhere between 250-325 yards, which will change the rate at which the bullet's effective BC decreases beyond that distance.

Bottom line is, your load more than likely provides the minimum remaining velocity (1,050 fps per Barnes' website) needed at 300 yards to ensure adequate expansion, but I wouldn't take a poke at a muley with it unless I'd first put a few 5-shot groups into a dessert plate sized circle at that range under approximate field conditions. In your shoes, I'd zero at 100 yards, test groups at 150 and 200 to find true holdovers, and definitely keep my shots under 200 yards this season. Then I'd spend some range time over the next year finding out just how good I can group out to 300 before next fall.

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DesertBoy said:

Far Sighted that’s what my shooters app is saying as well. When I ran my numbers, I had .28 in for B.C by mistake. With the correct B.C of .24, I am at 1257fps velocity, and 1017ft lbs. Looks like I would need a little more velocity to ethically shoot at that range.

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michiganmuzzy said:

Still, a 300yd shot is a long way for most shooters. Know your limits. Practice a lot. Maintain your equipment. Practice a lot. Be consistent. Practice a lot.

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