Using Ballistics Program To Find Speed ?

[67rschev]

I was just wondering if someone could use JBL to find his bullet speed . I have all of the other variables temp , altitude , barro , and on the money drops . Plugged in the variables , and increased the speed till my drops matched up with what I was shooting today out to 600 . The speed I came up with , was warpin' compared to what I was guessing on my original dope . I know I need to break down and get a chrono , and I am doing this all backwards , but was curious on how fast this new barrel is compared to the old one . Is 2900 fps a reality from a 22 inch Obermeyer .298 5r with 168s ?

 

[DougMH]

I was just wondering if someone could use JBL to find his bullet speed . I have all of the other variables temp , altitude , barro , and on the money drops . Plugged in the variables , and increased the speed till my drops matched up with what I was shooting today out to 600 . The speed I came up with , was warpin' compared to what I was guessing on my original dope . I know I need to break down and get a chrono , and I am doing this all backwards , but was curious on how fast this new barrel is compared to the old one . Is 2900 fps a reality from a 22 inch Obermeyer .298 5r with 168s ?

I'd say get the Chrony. I personally believe fairly inexpensive chronographs like the Shooting Chrony and others DO a great job of getting you to an MV area you desire. I DO NOT believe they're extremely precise and are prone to errors... reported on the display or not.

If you're patient, I may have a Shooting Chrony available for a good price in about a month. I bought an Oehler 35P off eBay and will be testing the two together over the next months. The Oehler is actually two chronographs. It has a primary and a proof. If the two are in sync, the reading is usable, if not, the printer prints an "*" to indicate you shouldn't rely on the reading for that round. This is where it excels over less expensive chronographs.

 

[hmcsr]

This doesn't answer your question, but I have CED millenium chronograph for sale. Price is $100 plus shipping. Includes an extra set of sky-screens.
I replaced it with the CED M2 to be able to collect more velocities.

Bill 8)

 

[markr]

You might get close trying to backwards engineer your results with components and drop tables, but thats about it. If you want to know the actual MV, you'll have to use a chronograph...then your drop tables may or may not closely approximate your results from the chrono.

 

[dooley]

Re using ballistics program to find speed, I believe you can approx find speed by elevation moa, however nothing replaces a chronograph however cheap it may be, over 20 years ago I was telling a friend on the range who was using a cheap chrony that he should get an Oehler like mine which I thought would be far more accurate, the results amazed me, I stood the cheap chrony in front of the oehler at approx 12 feet away and proceeded to fire different cals through both of them, there was never more than a few fps difference between them firing 10 shot strings, I even put them side by side, the differences were even less, sometimes the difference was only 1 fps, I currently have a oehler 35 and a CED mk 2, but I will never again disregard the accuracy of the cheap chronys, dooley UK

 

[joejo]

i agree with dooley.
i used my chrony in front and behind my friend ced2 and they never were inconsistant of one another.

 

[Zia Hunter]

JBL is a dandy little program and use it extensively. It deals with exterior ballistics once a velocity and other variables are known. I wouldn't recommend solving for velocity based as you mentioned above. As stated in the other posts, first recommendation would be to get or borrow a chronograph. Another option would be to calculate estimated velocities in Quick Load. It will get you close but not as good as a chronograph.

 

[67rschev]

You are all correct and the chono is on the short list for me . I have had access to one the past few years , and I know what a valuable tool they are for us . Unfortunately , the Alpha met its demise with an incident last year . I was not there to witness it , but saw the carnage afterward .

I'm thinking that new Magnatron may be worth the cheddar , as setting up a conventional can be a real PITA .

Back to my original question , anyone shooting 168 smks at over 2900 ? My old pet was only clocking 2630 , all be it a full grain shy of this load , but in a 4 inch longer barrel ( JBL dopes were right on 200 and further ) . Hoping I got a super fast barrel . For giggles , when I do run this loading I will post what it is averaging to see how backwards engineering of JBL stacks up .