Post by: Duckslayer89 on September 26, 2018, 09:00:19 PM
7mm Rem mag 180 grain berger vld, 2850 FPS and 1.75 inch seight height 26 inch barrel.
Zero=100
200 yards = 1.25 MOA ADJUSTMENT
300= 3.25 adjustment
400= 5.25 adjustment
My question is is there any way to input this information to see what my drop will be at 500,600,700 using the hands on data?
Post by: jmscon on September 26, 2018, 09:21:00 PM
Not sure if that answered your question.
Post by: Duckslayer89 on September 26, 2018, 09:42:24 PM
From what I understand your chromo isn’t always accurate and you can play with the FPS on the app to get your real-time results. That will give you a better idea of your adjustments for longer range.
Not sure if that answered your question.
Ok I never actually chronographed it I took the information from the guy who did the load work, he told me it was possible the barrel would speed up with more shooting maybe that’s what happened. I’ll play with the FPS and see if it makes more sense. Good idea! He was also at like 0ft elevation I was shooting at 2500ft
Post by: Stein on September 27, 2018, 04:29:34 AM
Post by: Curly on September 27, 2018, 05:15:01 AM
Post by: Yondering on September 27, 2018, 09:47:58 AM
Input your drops on most ballistic apps and it will calculate your fps as well as drops at any range you want. Measured or load fps is not much value as they are notoriously inaccurate.
Strelok does this but it's not a very good method. Your actual measured velocity is not "notoriously inaccurate"; it's actually pretty close if you measure more than just a couple shots. Strelok corrects the wrong variable IMO.
The bit that's "notoriously inaccurate" is advertised b.c. values for whatever bullet you're using. If you can use Litz values, that's better, but best is still to use a corrected value for your load and your gun.
The other big source of error is the initial zero. Guys shooting 3 rounds to zero at 100 are probably not really zeroed. If you go back and confirm that with 10 or more rounds on target at 100, you'll probably find that your zero is off a bit. Just an inch, or even a half inch, away from the bullseye can make a big difference down range.
Also make sure your atmospheric inputs are correct. Temperature, air pressure/density, and altitude are the most important, humidity is less important.
Post by: Stein on September 27, 2018, 10:09:41 AM
Fortunately it is easy to use actual drops and Litz values for many bullets as you mentioned.
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Post by: N7XW on September 27, 2018, 11:31:40 AM
:twocents:
Post by: Bushcraft on September 27, 2018, 11:50:18 AM
Couple points:
- I strongly recommend using a Magnetospeed over optical chronographs. The latter are intrinsically not as accurate or repeatable.
- It's not absolutely critical, but you should try and obtain the most precise zero height and offset as possible.
-You MUST utilize an environmental zero. Meaning, in addition to all the usual stuff (zero height, zero range, velocity, BC, etc.), it also needs to incorporate your baseline environmental inputs like temp, pressure (always use absolute), humidity, etc. All these change and it is important that your ballistic calculator incorporate this when performing it's calculation.
- If possible, perform velocity validation at extended ranges under identical environmental conditions as your 100 yard zero conditions. Meaning, don't plan on getting useful ballistic curve/drop velocity validation information if you are zeroing at sea level on a high-pressure cold day and then try a few days later to check long range drops at 10,000 feet on a hot low-pressure day. You'll just be setting yourself up for frustration in the future.
- Tweak your velocity first. If needed, and only if needed, then fine tune the B.C. minimally.
I use the Shooter app by Kennedy Development. It has a very large bullet library and many widely used target and hunting bullets have Litz verified info. Very easy interface (both setup and use) that intrinsically makes sense to me and the students that have taken my class. Unlike a lot of apps it allows for absolute zero inputs.
Post by: Yondering on September 27, 2018, 04:15:21 PM
- Tweak your velocity first. If needed, and only if needed, then fine tune the B.C. minimally.
If you're already using Litz b.c. values, maybe. If you're using advertised b.c. values, it's counter productive to adjust velocity first.
A couple of you guys are implying that chronograph measurements are a lot less accurate than they actually are. This is true for an individual shot, but when you combine measurements of a larger number of shots the measurement precision is a lot better. If you have to "correct" velocity by a significant amount from there, something else is wrong that should be corrected first.
If you are just using the advertised velocity on the ammo box, then definitely correct that first.
Post by: elj_1973 on September 28, 2018, 04:19:04 AM
yards MOA
300 = 3.2
400 =5.4
500 =7.8
700 =13.1
800 =16.1
Close to what your numbers are may be his chorno was off when he gave you the 2850 fps number, cause that speed looks like what most max book loads are listed for the vld 180 :twocents:. There is a free ballistic program that will let you true your velocities here is the link: http://www.gunwerks.com/ballistics. Hope that helps