inerlogic
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xtry51 said:Which was the most accurate?
ETA: I've learned to not rely heavily on chrono data from different sessions. Try this next time you're at the range with your chrono: Measure a few rounds, then twist your chrono a few degrees so that the rounds pass over at a slight angle, and check a few more. You'll shit.
I would think it is much more sensitive to the coplanarity of the beams. If the chrono wasn't unfolded exactly 180 degrees or the two sensors weren't parallel it would be a much bigger error than having a slight angle between the projectile crossing the beams. It's a cosine of a small angle effect so 5 degrees would only be a 0.4% error (cos 5) and 10 degrees would only be a 1.5% error (cos 10).
It ends up being worse than that because the beams are cones and not lines, and the sensors' ability to pick up an object is greater near the middle of the cone. If you send the bullet through the sensors on the outsides of the cones (as opposed to down the middle), or through the middle of one beam and near the outside of the other, not only are the beams farther apart, but the bullet has to travel farther into one of the sensing beams to be picked up by the sensor.
Remember, we're talking about the error when you set the chrono up for a new session and compare it to the readings from a previous setup. Distance to the chrono is on factor, the 'levelness' and alignment can also introduce error.
I'm only looking for best groupings though, which for me so far haven't been at anywhere near max loads, so the chrono data is more just for my general knowledge. Also, as stated above, it adds confidence that I'm staying away from the pipe bomb zone
You're right in line with my experience. At 25.0 with a max of 25.5, you're at 98%. In my experience, the chrono data in the manuals is often optimistic.Feedback?
You're right in line with my experience. At 25.0 with a max of 25.5, you're at 98%. In my experience, the chrono data in the manuals is often optimistic.
Also, if you're getting your data off the Hodgdon website, keep in mind that their velocity was measured in a rifle with a 24" barrel. If you're shooting an M4 or even a 20" barrel, your velocity will be lower. You're pretty much 'near max'.
ETA: Their barrel also has a 1:12 twist. A slower twist rate will give a higher velocity and a lower pressure. If you're using a 1:7 barrel, I bet you're AT max if you could measure the pressure.
I bet if you took your loads and fired them in their rifle, you'd be much closer to the 'book' velocity.
Some nice shooting there inerlogic!
I've used Varget in .223 with 55's, 69's and 75's. It's good stuff!