Hey guys, hoping to see if there is a way I can get a guesstimate of the FPS of my load without a chrono. Something that might give me a good enough baseline for using some ballistics software. I.E. My current load is a 69gr SMK, 26gr RL15, Federal Match Primer, coming out of a 26" barrel with a 1:9 twist. I would think somebody much much smarter than I am has figured this out. Thanks.
Is there a way to find FPS without a chrono?
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Zero at 100, then shoot a farther target without adjusting your scope, figure out your drop at that range in mils or moa, then with current environmental conditions and published specs on your projectile, drop reasonable velocities into a ballistics solver until you arrive at a velocity that produces the drop you saw on paper. My guess - 3100 - 3150fps
And since you said that you do not have a ballistic solver yet, one of the best available for free is JBM:
http://www.jbmballistics.com/ballistics/calculators/calculators.shtml
http://www.jbmballistics.com/ballistics/calculators/calculators.shtml
Or better yet, shoot at distance and dial your scope up.
I dont see why you think holding over would be more accurate than dialing exactly. Sure your tracking could be off but thats neither here or there in this scenario and should have been identified before this with a tracking test.
But yes, shoot at distance and back into the velocity by entering all the other parameters and seeing what velocity number lines up with your observed drop.
And the JBM ^^^^^^ is used by many other programs as well.
I dont see why you think holding over would be more accurate than dialing exactly. Sure your tracking could be off but thats neither here or there in this scenario and should have been identified before this with a tracking test.
But yes, shoot at distance and back into the velocity by entering all the other parameters and seeing what velocity number lines up with your observed drop.
And the JBM ^^^^^^ is used by many other programs as well.
I personally like iStrelok Pro. its always been dead on for me. its as accurate as my kestrel with AB on it when I put in the same wx and what not.
but as others have said you are prob in the 3100 fps range. so you could start there in your ballistic calc, then log your hits and what you need to actually dial to get center hits.
truthfully, with a ballistic solver you need to do this to true it anyway with actual hits out to range - and the further the better. even with a magspeed or labradar and a litz BC number or Doppler generated number doesn't guarantee perfect hits out to range in a ballistic calc.
but as others have said you are prob in the 3100 fps range. so you could start there in your ballistic calc, then log your hits and what you need to actually dial to get center hits.
truthfully, with a ballistic solver you need to do this to true it anyway with actual hits out to range - and the further the better. even with a magspeed or labradar and a litz BC number or Doppler generated number doesn't guarantee perfect hits out to range in a ballistic calc.
You either need to know BC or velocity. Some BC measurements have been made that would get you reasonably close using the method above
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