Velocity variation between shooters.

[yobuck]

Has anybody here ever experienced velocity differences from the same load, fired from the same gun, over the same chronograph, on the same day, by two different people?
Especially two different people with significant size differences?
Or, different velocities by the same person, when using different techniques like pressure of the cheek against the stock, or stock pressure against the shoulder?
Im talking considerable differences, not small, such as those found in what we call spread deviation.
And, could it be a cause of that?

[Robinhood]

I would be interested in empirical data

[yobuck]

I would be interested in empirical data
just asking, because on another site a guy who at least seems to have his stuff together, claims it happens.

[Robinhood]

Point of impact? Most definitely. There is nothing an operator can do to effect the pressure inside the case and chamber or barrel. If the barrel was hot and one shooter would wait for the flags to drop before he chambered the round and then fired within 5 seconds of closing the bolt and the other imediatly chambered the round and waited 15 plus seconds....absolutely.

[yobuck]

That would be my opinion also, but then I’ve never tried any of what he claims either.

[Stumpkiller]

I like Robinhood's analysis. Or, as the barrel became more fouled the later shooter might get slightly different velocities.

I've never observed or heard of such a thing happening. Be a good experiment.

If someone REALLY jerks the trigger the rifle is moving in an opposite vector to the bullet. ;-)

[Fuj']

Awhile back, I was doing some testing being down hard on
the rifle, in the bags, and then letting it free recoil. I was
looking for an accuracy factor between the two holds.
I fired 5 shots each.....Free recoil seemed to give me a
better group. Lab Radar gave me no indication there was
a velocity difference between the 2 sets.....Yeah it was
just me doing the shooting but the two methods used,
could simulate two different shooters.

[Shortbox4x4]

Off hand I’m going to say no but I will throw a but in there.

You need more information/data.

Do you know the caliber the rifle is in?
Do you know how often (between the number of rounds) it is being cleaned?
Actual load data?

Things can cause pressure spikes/velocity changes but going from a shooter to shooter....I’ll say no.

With out knowing the above information....your guessing. I’ve seen calibers/rifles/test barrels call it what you want that with out proper cleaning and the caliber it is in or if the barrel/rifle has issues that with in 20 rounds you get a velocity/pressure change. So if that is happening imagine you go from one shooter that put say 15-20 rounds thru it and the next guy sits down and keeps shooting but then sees a change and they think it because of a different shooter but it’s really not.

Later, Frank
Bartlein Barrels

[Miocene]

I have read a similar article theorizing variations in actual velocities. Shooter induced accuracy? Sure , even free recoilers to a less extent. But hard data to support variations in velocities from shooter to shooter must also certainly be affected by the other kabilion 'noise' generators as mention above. First instinctive thought to me would be no. Shooter induced variations in accuracy and precision. Sure.
Sometimes I forget the dumbest things and get into bench position to fire a string. I shoot free recoil with the lightest calibers and yep, position perfectly with the occasional large bore and bam! Genius. Odd thing is, I have seen that shot remain consistent within the rest of the group on some occasions. Point being, it really shouldn't. Who knows, even a shift in light /shadow on the chrony may even affect some machines in giving an erroneous speed. just slightly off unnoticed. Randomization and statistical chance seem to also play a part, skewing results or how we perceive these results. To me, the rabbit hole is deep.
But this seems like a good enough reason to have the wife sit on the bench behind the trigger. Pray for chrony's safety.

[Miocene]

Edit: On second thought, I don't think my processes, even as strictly methodical as they may be, would not represent two full strings of perfectly duplicated cartridges to fairly determine variation precisely due to shooter only. The controls would need to be extremely extensive.