Slugs vs pellets and strelok app
- Thread starter Kevo4224
- Start date
For anyone wondering the twist rate of the 25cal heavy superior liner i added a photo above.
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Thanks you Kev, for not letting us hanging about the solution to your problem! 
I'm glad it worked out in the end for you.
I still a little surprised at the low BC. 
▪Could have something to do with being only 0—40y, as you're shooting them pretty fast (i.e., transconic, where drag is excessive) — once you get further down range and their speed decreases the BC should increase.
However, 0.055 still seems low.
▪What calculator did you use (because there are some out there that do not use the GA or G1 drag model, and others that don't have any way to adjust for the atmospheric conditions, etc.)
Matthias
I'm glad it worked out in the end for you.
I still a little surprised at the low BC. ▪Could have something to do with being only 0—40y, as you're shooting them pretty fast (i.e., transconic, where drag is excessive) — once you get further down range and their speed decreases the BC should increase.
However, 0.055 still seems low.
▪What calculator did you use (because there are some out there that do not use the GA or G1 drag model, and others that don't have any way to adjust for the atmospheric conditions, etc.)
Matthias
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No problem! I used a calculator off of jbmballistics.com, I was using the G1 drag function that it has when calculating my bc. Thank you for the advice jungle shooter. I have a gong at 77 yards and the stre lock app is on point with the current bc I have in the strelok app. What range do you think I should measure the velocity at and figure out the bc again? Yes I was suprised at the low bc as well, but like I said at 77 yards its still on. But like you said it might not be slowing down enough still at 77 yards possibly?
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I have the exact BC as you shooting them from cricket .25 at 870 ,I came up with BC of .052 its low for slug but they are very accurate .
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Kevo,
well, you already measured the BC at 40y, so that's a good value to start.
You used G1, which is fine for slugs.
The JBMBallistics should give you the option to enter atmospheric conditions of the test. Careful with the barometric pressure — the one in Strelok asks for your local pressure, not the pressure reported from a wheather station (and there are ways to convert that knowing your elevation and temperature).
If you are shooting good enough groups, for curiosity and precision sake, I would try to shoot 10 to 15 good shots over the chrono* at your gong range, 77y. You'll probably miss a few, but that's OK. Average the 10 shots where you get a realistic chrono reading, and calculate BC again, for 0—77y.
*[Yes, the chrono needs body armor, like a 1/2" acrylic glass face plate.
Unless you're THAT GOOD....!]
You can also calculate BC from 40—77y. Then you have two BC values, for two different average velocities. If they are significantly different, you can enter them into Strelok which has an option for multiple BC's. Then your really long shots beyond 100y will have a more realistic BC to work with.
Lot's of fun testing, tweaking, and figuring things out. I'll be doing the same very soon, too.
Matthias
well, you already measured the BC at 40y, so that's a good value to start.
You used G1, which is fine for slugs.
The JBMBallistics should give you the option to enter atmospheric conditions of the test. Careful with the barometric pressure — the one in Strelok asks for your local pressure, not the pressure reported from a wheather station (and there are ways to convert that knowing your elevation and temperature).
If you are shooting good enough groups, for curiosity and precision sake, I would try to shoot 10 to 15 good shots over the chrono* at your gong range, 77y. You'll probably miss a few, but that's OK. Average the 10 shots where you get a realistic chrono reading, and calculate BC again, for 0—77y.
*[Yes, the chrono needs body armor, like a 1/2" acrylic glass face plate.
Unless you're THAT GOOD....!]You can also calculate BC from 40—77y. Then you have two BC values, for two different average velocities. If they are significantly different, you can enter them into Strelok which has an option for multiple BC's. Then your really long shots beyond 100y will have a more realistic BC to work with.
Lot's of fun testing, tweaking, and figuring things out. I'll be doing the same very soon, too.
Matthias
Upvote 0