hard time measuring powder

[MCMXI]

Time in the barrel. The barrel is rising in recoil.

Hmmmm ... what if the barrel were fixed in a vice?

Wouldn't less powder result in less recoil i.e. less muzzle rise? Would the reduction in muzzle rise offset the "longer" time of the bullet in the barrel? In real world terms, what is the difference in time-in-the-barrel for min/max loads?

 

[RidgwayCO]

I don't let my guns hang around with the wrong sort, so they have no vices... fixed or otherwise.

Walkalong is correct (assuming the gun is not fixed in a vise to prevent muzzle rise). Recoil begins the moment the primer ignites and continues until the expanding gases depart the barrel, which causes the muzzle to rise due to the shape and position of the grips. The slower the bullet is traveling, the longer it stays in the barrel and the more it is affected by the muzzle rise. So faster bullets generally hit lower than slower bullets.

And don't even get me started on exterior ballistics...

 

[MCMXI]

Ballistic calculators are next to useless then since they obviously don't take muzzle rise or recoil into consideration. It would be interesting to see what the difference in time-in-barrel is for the two loads below. This is a bit simplistic since I used MV/2 as the average velocity in the barrel but I calculated something on the order of 0.0010 seconds for the min. load and 0.0008 seconds for the max. load i.e. a difference of 0.0002 seconds. The loads in the figure are straight out of Lyman's 49th Edition ... 230gr TMJ, 700X powder, 3.6gr and 4.8gr. I'm not trying to start an argument here, I'm just trying to understand this phenomenon that seems counter intuitive.

 

[jcwit]

Just a thought here. Aren't we going a little to the extreme with bullet time in barrel changing POI 6 inches at 21 feet?

 

[Walkalong]

Yes, I seriously doubt that accounts for it all. Maybe a third or half of it.

 

[MCMXI]

Well, look at the figures above for the min and max loads, the POI changes by only 2" at 50 yards (150 feet!!) so a 6" change in POI at 21 feet is OBVIOUSLY due to something else. Short of being WAY too low on the charge, which is possible, or the sights mysteriously moving which is also possible, I'd have to suggest it's PIO.

 

[jcwit]

PIO---?

 

[MCMXI]

Pilot Induced Oscillation ... ... and no, I'm not a pilot ... a couple of friends are pilots for American and JAL and they throw these acronyms around from time to time.

 

[jcwit]

Got to admit thats a different way of putting it.

 

[RidgwayCO]

I think we're comparing apples and oranges here. The Hornady charts just show bullet drop when fired from a perfectly horizontal test barrel that's locked in place. The only thing working on those bullets once they exit the muzzle is air resistance, any wind, and gravity (all being accounted for in exterior ballistics), because the barrel can't move except for it's normal harmonics.

But we're talking about the barrel itself moving from recoil when hand-held during firing. I think you'll agree, it doesn't take much muzzle movement to greatly affect bullet impact location (point of impact or POI) during regular firing. The tiny differences in barrel dwell time can lead to small differences in muzzle elevation at bullet exit, which can lead to big differences in where the bullet impacts the target (or off the target...), depending on how far away the target's located.

There, that should be clear as mud...

 

[Walkalong]

Well, look at the figures above for the min and max loads, the POI changes by only 2" at 50 yards

That isn't how it is figured. There are no charts for it either.

Gun weight, strength of hold, bullet weight/velocity, barrel length, barrel time.

No way to chart it.

Pilot Induced Oscillation

My father flew in the USAF. He would recognize that. Actually, although I just thought PIO was a typo, when you typed it out, it did sound familiar.

 

[jcwit]

Add something else to this.

The most accurate target .22 rimfire ammo is the sub sonic to std. vel. ammo, and I don't mean the inexpensive ammo, I'm talking about the $100 to $200 a brick stuff.

Long time before it exits the barrel.