DT338LM
Active Member
I zero at 100 and then valdate my speed at 700. I always find the magneto speed to be slow by 40 -75 fps. What you guys get for results?
Magneto Speed
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Barrelnut
Well-Known Member
I zero at 200 and validate at 700. I found it to be about 40~60 FPS too fast.
I kid you not.
My theory is it has more to do with the actual BC of the bullet than the speed determined by the Magneto Speed.
I kid you not.
My theory is it has more to do with the actual BC of the bullet than the speed determined by the Magneto Speed.
J E Custom
Well-Known Member
I don't understand how you validate at 700 yards ? the Magneto speed chronograph measure velocity at the muzzle. it doesn't matter what distance you shoot. If you shoot 700 yards and use the listed load velocities based on drop, the bullet BCs are not correct or the actual velocity at the muzzle doesn't match the listed velocity in the loading manual because of barrel quality or length.
Don't go buy the listed velocity check your velocity with another chronograph to see if your Magneto Speed is accurate and go with the velocity at the muzzle, not listed velocities. muzzle velocities are the most accurate because they eliminate any error caused by conditions that can/could effect the bullet.
I have tested my Magneto Speed against a lab quality chronograph and found mine to be spot on with muzzles velocity. If you place the screens for measurement 10 to 30 feet away from the muzzle you will get a lower muzzle velocity because of the distance.
On a three screen setup, there is a drop from the proof screen and the measurement screen. and that is only 2 to 4 feet in most cases.
Hope this helps
J E CUSTOM
Don't go buy the listed velocity check your velocity with another chronograph to see if your Magneto Speed is accurate and go with the velocity at the muzzle, not listed velocities. muzzle velocities are the most accurate because they eliminate any error caused by conditions that can/could effect the bullet.
I have tested my Magneto Speed against a lab quality chronograph and found mine to be spot on with muzzles velocity. If you place the screens for measurement 10 to 30 feet away from the muzzle you will get a lower muzzle velocity because of the distance.
On a three screen setup, there is a drop from the proof screen and the measurement screen. and that is only 2 to 4 feet in most cases.
Hope this helps
J E CUSTOM
Barrelnut
Well-Known Member
I think, we are talking about zeroing and using the MS at 100 or 200 yards. Then taking the MS off and shooting 700 yards and finding the dialed dope to be off. Then having adjust the velocity in the ballistics calculator to match the dope dialed.
DT338LM
Active Member
In the ballistic program i use there is a place to validate muzzle velocity. I don't use factory ammo. I reload everything i shoot. I use the magneto speed as a reloading tool and a drop chart tool. After i have my rifle zeroed at 100 i shoot at 700. From there i measure how many moa im off. When i input the new info in the ballistic program my new muzzle velocity always increases ..
That's the question im asking. I never been able to use my muzzle velocity from my magneto speed to give my a correct correction. I always tweaked it
DT338LM
Active Member
Exactly....
Ladd-
Well-Known Member
I just read this article about this subject. It's a good read.
http://panhandleprecision.com/trajectory-validation-ten-steps-success/
http://panhandleprecision.com/trajectory-validation-ten-steps-success/
J E Custom
Well-Known Member
You are doing everything right, but to get the adjusted BC of the bullet you have to use the muzzle velocity of the chronograph.
change the Bullet BC to match the trajectory on the bullet to the actual trajectory using the muzzle velocity you have.
Conditions, altitude, temperature and many other factors have a effect on the bullet performance and most bullets have 3 different BCs during the flight to target.
Living on the gulf coast, I have to use different Bullet BCs than the manufacture claims to get trajectories that match charted/calculated velocities.
This is not uncommon and is the best way to get good information to input into ballistic calculators. Before these tools were available, we used drop charts and the chronograph to get unknown zeros for match shooting. These distances could change from 200 yards to 1200 yards depending on the match. and most of us may only have access to 600 yard ranges to verify all zeros.
Keep changing the bullet BC until you get a close match.
J E CUSTOM
change the Bullet BC to match the trajectory on the bullet to the actual trajectory using the muzzle velocity you have.
Conditions, altitude, temperature and many other factors have a effect on the bullet performance and most bullets have 3 different BCs during the flight to target.
Living on the gulf coast, I have to use different Bullet BCs than the manufacture claims to get trajectories that match charted/calculated velocities.
This is not uncommon and is the best way to get good information to input into ballistic calculators. Before these tools were available, we used drop charts and the chronograph to get unknown zeros for match shooting. These distances could change from 200 yards to 1200 yards depending on the match. and most of us may only have access to 600 yard ranges to verify all zeros.
Keep changing the bullet BC until you get a close match.
J E CUSTOM
jasent
Well-Known Member
Always adjust bc first.
Lot to lot deviation, how your barrel ingraves the bullet, the speed your shooting the bullet, ect all have a effect on the bc
Lot to lot deviation, how your barrel ingraves the bullet, the speed your shooting the bullet, ect all have a effect on the bc
snox801
Well-Known Member
I'm glad you brought that up JE. I just watched a gumworks video were they adjusted speed to match and thought wth? They went with the published BC which we all know they would never lie about to increase sales. Wink wink nosler.
At least use a applied tested bc. I bet if you use the bc supplied by applied and your magneto speed you would be on. I've been able to take my speed and use the applied bc for said bullet and make hits on target where they should be. Lots of factors but why change a known variable when you have one that is unknown. The bc. Adjust that not a know speed.
At least use a applied tested bc. I bet if you use the bc supplied by applied and your magneto speed you would be on. I've been able to take my speed and use the applied bc for said bullet and make hits on target where they should be. Lots of factors but why change a known variable when you have one that is unknown. The bc. Adjust that not a know speed.
For my precision shooting out to 1000+yards establishiing an "accurate" muzzle velocity, and subsequently adjusting BC at the longer ranges has always produced the most accurate results. I own an Oehler 35P, Lab Radar, and Magnetospeed. While the Ohler takes some care in set-up and lighting conditions, I have found that the three chronographs are within 10 FPS of each other. Before the MS and LR, I almost slways calibrated with velocity due to the uncertainty of my velocities with the optical chronographs. It would certainly work at the midrange, but lacked accuracy at the longer ranges. Given that the environmental conditions taken into account when establishing my zero, and the particular load has an acceptable ES and displays good consistency, I'll tune the BC to point of impact at 500-1000 yards for both my hunting and competition rifles. I will believe the results from the Magnetospeed or Lab Radar MUCH more so then the reported BC for a given bullet, primarily because it can vary with a particular barrel and/or loading parameters. IMO.
J E Custom
Well-Known Member
Before we had quality chronographs, or no chronograph at all we established muzzle velocity using drop charts. Once we found the actual drop at known distances we could calculate the Bullet BC and the actual velocity.
The only thing that we could count on was the actual drop chart. Sight settings/changes required good drop charts that matched the rifle and ammo used when changing distances during a match. we realy didn't worry about bullet BCs because of climate and altitude changes. and because most advertised BCs were incorrect for out location.
Things have definitely changed for the better
J E CUSTOM
The only thing that we could count on was the actual drop chart. Sight settings/changes required good drop charts that matched the rifle and ammo used when changing distances during a match. we realy didn't worry about bullet BCs because of climate and altitude changes. and because most advertised BCs were incorrect for out location.
Things have definitely changed for the better
J E CUSTOM
bigngreen
Well-Known Member
I have yet to tune the velocity more than 10 fps or so to 1000 yards and I don't tune BC till very close to transonic. The better data I use for set up and environmental the less tuning I need to do. You HAVE to verify your 100 yard zero at 300 ish, but his is one of the biggest issues many run into IMO.
Barrelnut
Well-Known Member
I tend to use the Shooter and Applied Ballistics ballistics apps. Within them I use the Litz verified bullet profiles in Shooter and the "Custom Drag Models" in AI. The BC in these profiles are non adjustable. After verifying scope clicks with a tall target test and making any adjustments needed in the apps to true the scope clicks, I shoot at 700 yards and make changes in velocity to true the app results to the physical results at 700 yards. Once this is done things from zero to 1K tend to line up very well.
