I’m having difficulty finding the incorrect value in my calculations. I’m shooting a Savage AR15 223. The ammo is IMI Razorcore 77 grain SMK with a .372 G1. I don’t have a chronograph but have seen videos showing 2727 FPS out of a 16” barrel. So I use 2727 for the muzzle velocity. At 500 yards, the elevation shows to be 12.16 come up. But when I shoot it’s very high. I dialed down to 9.25 come up and shot a 4 inch group at 500. Nearly 2 MOA is a significant difference in the dope at 500 yards. Heck, if 9.25 is correct, that would put muzzle velocity over 3000 FPS which we know isn’t correct for the 77 grain. The published velocity is 2740. Does anyone know what the problem could be?
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The scope height is set at 1.5”. I just used that by default. Even if it’s 2 inches, that would only change the come up slightly at 500 yards and nowhere close to the nearly 2 MOA I’m off. I now wonder if somehow I ranged the yardage incorrectly….somehow. When I shoot different yardages, I move to another area of the farm and move the target to whatever yardage I want to shoot (the topography is perfect for it). Do you guys come up with the same come up as my 12.16 plus or minus a little. If so, I must have messed up on ranging the target.Last edited by PVDT; 02-20-2022, 02:35 PM.
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I say a compounding of errors. Scope height, velocity, BC, and (probably primarily) scope tracking.
Get the numbers right in the calculator and do a tall target test and get back to us.
What calculator are you using? I’ve found the Hornady 4DOF to be dang near perfect with everything I’ve put in it.
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Originally posted by bearintex View PostI say a compounding of errors. Scope height, velocity, BC, and (probably primarily) scope tracking.
Get the numbers right in the calculator and do a tall target test and get back to us.
What calculator are you using? I’ve found the Hornady 4DOF to be dang near perfect with everything I’ve put in it.
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IMO, a chronograph is the single most important tool when reloading, shooting for accuracy, and trying to find your long-range dope.
Without a chrono you're wasting your time. A barrel will have certain "accuracy nodes" that are based on velocity. Your barrel might shoot a 1-hole group at 2750 fps, BUT it could become a 1" group at 2650 fps.
buy a $200-300 chrono and it will make your shooting life so much easier. Many times the velocity printed on the side of a box of factory ammo is not even close to real world shooting conditions.
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Originally posted by ORIONTHEHUNTER View PostIt's amazing people would try to shoot long range and not chronograph their rifle and loads. Also are you using a g1 or g7 ballistic coefficient in your program?
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I’d do a tracking test first for sure. If the scope isn’t proven, need to get that handled first and foremost. I usually do mine at 200yds. Have a target that’s at least 4ft top to bottom, the bigger the better. I test mine at least 5moa up/down/left/right and it should all come back to zero at the end.
Past that, I’m not wise enough to know what the issue could be. Before I got a chrono I just went off the listed muzzle velocity for my calculations, and then adjusted the velocity input up/down until it matched what I was seeing on paper for 2/3/400yds. So a chrono isn’t a MUST when you have all the other data available, but is definitely the best option.
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