Quote:


You'll have tell the 22rf shooter that 

Frank

I have been told that the 22LR is being shot at out to 300 yards at gongs.  At my range, we shoot out to 200 meters at reduced size silhouettes.  That is a hoot, if you can see them at that range.  A 6x MVA comes in handy for me when shooting the rams at 200m, since the grass usually obscures the bottom half of the animal.

Keeping track of the wind is the key to success.

Keep on hav'n fun!
MikeT

For the long range shooters, there are two components to high and low hits. One is the extreme spreads in velocity and the other, 6 and 12 o'clock winds or winds close to that. 

Frank

   One remark on velocity considerations.   The old timers quickly found that ctgs like the 44-77 were not competitive at 1000 yd with e.g. 44-90.   My take on that is that you can pencil out that vertical dispersion with change in muzzle velocity goes about inversely with the cube of the velocity.
   They didn't have the good chronographs that we have that would enable them to refine their loadings to give minimal velocity dispersion.   A 10% increase in velocity would cut their vertical from that cause by about 30%.  The velocity increase would give increased wind drift, but you can dope for that.
   My opinion is that that is the reason for their desire for higher velocity.
   I have been loading a TD 45-70 down to ca 1100 fps and have good results with it to 600 yd, because the velocity dispersion SD is down in low single digits.  Also, it doesn't slap the snot out of you like the full "war loads". 

CHRIS
RGChristensen

I believe what might not be taken into consideration is that the muzzle must stop at the same point each time it releases the bullet or minimal verticle dispersion would simply not be obtainable. Finding a correct node in the barrel whipping cycle for this to take place is also controlled by velocity and this is where the real world part of the equation comes into play as every barrel / wieght / length / action attachment provides entirely different results. I am not sure how math can accurately take all of this into consideration. On another note but maybe relevent knowing that barrels are not perfectly straight should the curve be oriented at 12 o'clock top dead center or down at 6 o'clock to assist in achieving that correct muzzle stopping point while not also inadvertently introducing any horizontal.

JLouis

JLouis wrote on Mar 29^th, 2014 at 12:02am:

That one's the tricky one - the best place for the bullet to exit is either at the top or bottolm of the movement, where the barrel stops to return.  I fail to see how math can give me an accurate calculation of this...
Still, if it were easy, it for sure wouldn't be fun...

My wife is a competitive American Rimfire Association (ARA) shooter. I'm the pit crew and chief roadie.

Tuning is fundamental to success in rimfire competition and we are blessed with a seemingly endless supply of "tools" (mid-barrel tuners, end-barrel tuners, deresonators, slides, etc.) to help achieve that elusive perfect state of tune.  

The theory is simple, we want the bullet to exist the barrel as the muzzle is moving upward.  In this happy state faster moving bullets exit earlier than slower moving bullets.  Since the barrel is moving upward, the slower moving bullets exit at a launch angle that is steeper than the launch angle of the faster moving bullets.

This state of bliss is known as positive compensation and helps minimize the vertical dispersion that would result if both the faster moving bullet and the slower moving bullet existed the muzzle at the same launch angle.

While the tuning process can be modeled, the only practical way to tune a given rifle is through very tedious and often frustrating trial and error.

But, for those inquiring minds that wish to dive a little deeper into the subject, Varmint Al has a very technical webpage on the subject - complete with FEA - enjoy: (You need to Login or Register to view media files and links).

JackHughs      

I'll take a stab at it ...

There may very well be some eccentric forces from residual stresses in the barrel that impart non-vertical oscilations, but whereas the end of the barrel is affected by gravity, it (end) moves in a sine wave pattern.

At the top and bottom of the sine curve there is very little vertical dispersion, more left to right or X axis variation. While in the middle of the curve , say on a really steep section, for just a little X axis movement, you'd get a tremendous vertical jump.

Note, a real barrel doesn't move left to right, but the axis 'ripples' in the sine wave pattern, from chsnber to muzzle.