A while back there was a post (and video) about muzzle velocity (MV) not being the same prone versus sitting at the bench. There was also thorough research/measurement done by Bryan at Applied Ballistics and detailed in one of his books, for testing chronographs. I want to throw caution to the wind presenting my take...
I am an engineer, old enough to likely be losing it, but I still recall some Physics, and the concept of "measurements depend on the location of the observer, i.e. where is the measuring device". ...patience, do read on...
To me we use the term MV in conflicting ways, and not all measurements we take are the same. MV means the velocity of the bullet as it leaves the muzzle, that is the velocity of the exiting bullet as referenced to the muzzle. Of all the chronographs I am aware of, only MagnetoSpeed measures this, since it is attached to the barrel at the muzzle -- the observer is sitting on the muzzle, and thus the motion of the muzzle (as in recoil) is irrelevant. All the other chronographs, including LabRadar measure bullet velocity with reference to the ground -- the observer is sitting on a chair next to you. There is a difference.... for LAbRadar measurements, the motion of the barrel/rifle under recoil is taken into account. I suggest below you have both, a MagnetoSpeed and a land referenced chronograph if you want to master consistency in recoil management.
Since MagnetoSpeed measures the bullet speed in relation to the barrel's muzzle, it is quite isolated from how you handle recoil, or how consistent you are in handling recoil -- the rifle could be bolted to a concrete block, or it could be on a soft shoulder that reacts differently every shot, and theoretically the measurements should be the same, all other variables being equal. Thus Magneto's give you the best idea on the consistency of your reloads; since the variation in measured velocity should only be due to your loaded cartridges.
However, bullet trajectory is referenced to land. The rifle in on a spot on the land, target is on land, and at a distance away from you on land, so we need the velocity of the bullet as it leaves the rifle with reference to land -- ideally the rifle would be perfectly bolted to the ground, but that is not the case. This is what the other chronographs measure, and this is where we the shooters can screw things up by managing recoil inconsistently. Not only will the measured LabRadar velocity vary because of powder load/case capacity variations, it will vary because we may not be managing recoil in the exact same way shot after shot and from position to position, as was observed in the post mentioned above.
So by using a Magneto-obtained MV standard deviation (Sd) and then obtaining a LabRadar Sd we can see how good we are at being consistent managing recoil. Theoretically LabRadar Sd will be higher than Magneto Sd., provided your handloads are very consistent. The closer you can get the LabRadar Sd to the Magneto Sd the more consistent you are being at managing recoil, and the more trustworthy your ballistic solution will be. The more consistent the more trust we can put into the LabRadar-measured MV that we input to our ballistic calculator.
I do not know what the measurement error is for either the Magneto or LabRadar, and it would be good to know, as this error will be reflected in the respective Sd's.
...just some thoughts... any comments ?
-njaimo
I am an engineer, old enough to likely be losing it, but I still recall some Physics, and the concept of "measurements depend on the location of the observer, i.e. where is the measuring device". ...patience, do read on...
To me we use the term MV in conflicting ways, and not all measurements we take are the same. MV means the velocity of the bullet as it leaves the muzzle, that is the velocity of the exiting bullet as referenced to the muzzle. Of all the chronographs I am aware of, only MagnetoSpeed measures this, since it is attached to the barrel at the muzzle -- the observer is sitting on the muzzle, and thus the motion of the muzzle (as in recoil) is irrelevant. All the other chronographs, including LabRadar measure bullet velocity with reference to the ground -- the observer is sitting on a chair next to you. There is a difference.... for LAbRadar measurements, the motion of the barrel/rifle under recoil is taken into account. I suggest below you have both, a MagnetoSpeed and a land referenced chronograph if you want to master consistency in recoil management.
Since MagnetoSpeed measures the bullet speed in relation to the barrel's muzzle, it is quite isolated from how you handle recoil, or how consistent you are in handling recoil -- the rifle could be bolted to a concrete block, or it could be on a soft shoulder that reacts differently every shot, and theoretically the measurements should be the same, all other variables being equal. Thus Magneto's give you the best idea on the consistency of your reloads; since the variation in measured velocity should only be due to your loaded cartridges.
However, bullet trajectory is referenced to land. The rifle in on a spot on the land, target is on land, and at a distance away from you on land, so we need the velocity of the bullet as it leaves the rifle with reference to land -- ideally the rifle would be perfectly bolted to the ground, but that is not the case. This is what the other chronographs measure, and this is where we the shooters can screw things up by managing recoil inconsistently. Not only will the measured LabRadar velocity vary because of powder load/case capacity variations, it will vary because we may not be managing recoil in the exact same way shot after shot and from position to position, as was observed in the post mentioned above.
So by using a Magneto-obtained MV standard deviation (Sd) and then obtaining a LabRadar Sd we can see how good we are at being consistent managing recoil. Theoretically LabRadar Sd will be higher than Magneto Sd., provided your handloads are very consistent. The closer you can get the LabRadar Sd to the Magneto Sd the more consistent you are being at managing recoil, and the more trustworthy your ballistic solution will be. The more consistent the more trust we can put into the LabRadar-measured MV that we input to our ballistic calculator.
I do not know what the measurement error is for either the Magneto or LabRadar, and it would be good to know, as this error will be reflected in the respective Sd's.
...just some thoughts... any comments ?
-njaimo
