I am shooting a RPR 6.5CM, with a NF ATACR 5-25 on top. Sight height is 2.69". Using factory Nosler 140 BT ammo. BC is .509 I believe if I remember that correctly. My velocity I got using an older F-1 chrono was 2473 fps ( yes I know that's slow). Chrono could be off. Shots sub moa at 100 consistently. I got a chance to verify my dope at 600 yards and 300 yards it turned out to be 4.5 mils and 0.9 mils respectively. I cannot get the dopes to match up in JBM or iSnipe. I can obviously get one of the yardage settings to line up but cannot get both together. I messed around quiet a bit with both the BC and velocity in the ballistics programs with zero luck. Any advice is appreciated.
Matching verified dope to ballistic software dope
- Thread starter Kramerica
- Start date
You want to true your program at the longest range possible. So I would use the 600 yard numbers. Also, I have a high scope, and mine's only 2.3" above bore. 2.69" is really high. Any error here will show itself more at closer distanced, so this could be why your 300 yard numbers are off so much. Are you confident in this number?
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Yes I'm pretty confident in my numbers. It's possible there slightly off but it's around 0.5 mils off on the program. I know I'm not that far off in my numbers. Hopefully heading to the range this weekend to try it again. only have 1/16" clearance between my objective on the scope and the barrel so it is as low as possible. I did play with that number too and it made almost no difference in the program. I'm stumped.
I'm a tad confused. You say that the BC is such and such, as you recall & the velocity is this, if it can be relied on.
Why not just live with what's reliable - where the bullet strikes?
Why not just live with what's reliable - where the bullet strikes?
I am but it'd be nice to get where the bullet strikes to match up with the ballistic program for when I go to a longer range.
Yes and yes
I take my previous post back. I took the owners word for it I didn't verify with my rangefinder. That would explain it for sure. If it's off just 25 yards my numbers do line up.. I'll check next time I go there again. Thanks.
CharlieNC
Gold $$ Contributor
You should be able to true it exactly. Also do a tall target test by dialing up 10 mils at 100 yards and if not exactly 36 inches up ( shoot 3 shots each ) then your app should have capability to enter the actual change per click. A few % error is not unusual and is significant.
I'll do that next time I'm at the range. I guess it's possible but Nightforces are usually spot on.
CharlieNC
Gold $$ Contributor
Jalen you may be surprised but the actual studies I have read indicate something on the order of 50% of scopes (high end tactical models by numerous mfg) have tracking inaccuracies. As long as the error is consistent across the entire range the compensation is easy. A 3% error is a big deal at longer ranges.
Could you post the link to the studies your referring to?
CharlieNC
Gold $$ Contributor
Snipers Hide killswitch studies
That was an interesting read, thanks for passing it along.
I have an old hand me down chronograph. I'm thinking it's reading wrong. I'm heading back out to the range tomorrow I'll have my buddy bring his
ballisticdaddy
Silver $$ Contributor
If you were to check the load data from Nosler they show the MV of this ammo at 2,650 FPS which is almost 200 FPS faster than what you had posted. If the variables loaded into any BC are inaccurate it is always going to provide an inaccurate solution.
You would be hard pressed to find any two barrels that shoot the same ammo at the same velocity. There are more variables outside the ammo than most people realize. Your chronograph may be off or it may be very accurate. You can try as many chronographs as you like but if the readings are comparable then you just have to accept that your gun has a "slow" barrel.
You need to get an average of at least 10 shots for the velocity, not just 1 or the fastest. And, are you calculating the actual muzzle velocity or just what reads on the chrono? The actual muzzle velocity could be from 5 to 10 fps faster. Look up the specs on your chrono and see what the margin of error is. Are you using G1 or G7 BC figures? Use G7 if you have the option. No program is going to be 100%. You'll need to adjust your inputs and see if it helps. Velocity will have more of an impact closer and BC farther out. It may be a balancing act between the 2 to get a little closer. Are you sure of the distances? At 600 yards with that slow of an MV, the bullet will be coming down at a pretty good angle. If you miss the distance even a few yards, it will either hit higher or lower.
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