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  #76  
Old 01-14-2022, 06:45 AM
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Studies done a few years back by cutting back a barrel from 24-inches, an inch at a time, and shooting with standard velocity ammo indicated that accuracy was not affected, but velocity was affected, with optimal velocity achieved at 18- to 19-inches. Prior to that length, due to the longer time in the barrel and the resulting friction on the bullet, velocity begins to decrease. After that length, shorter barrels resulted in the loss of velocity. This particular study only used one type of ammo and hi-speed or subsonic ammo and different brands will have different results.
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  #77  
Old 01-14-2022, 10:27 AM
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I understand that any bbl length exceeding 16 inches is superfluous with 22RF due to the internal ballistics of that round.
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  #78  
Old 01-14-2022, 10:30 AM
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I think that it depends on the powder that is in the cartridge whether or not the velocity increases or decreases when the barrel is shortened.
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  #79  
Old 01-14-2022, 12:19 PM
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Originally Posted by MKnarr View Post
I will admit to not being the sharpest tool in the box but I have problems with "Some ammo shoots better groups at 100 yards than 50 yards". I will assume that that statement does not mean that the groups are smaller at 100 than 50 but are smaller than one would expect from the LINE OF DEVIATION
IN the drawing below, I assume that gravity is uniform and in a tunnel there "should" be no wind deflection.


Here is my problem. If for whatever reason a round leaves the barrel that deviates from the line of sight and hits the target at 50 yards at point A and and another hits at point B, one would expect that the bullets wound continue on the LINE OF DEVIATION and end up at point AA and BB at 100 yards. But instead the bullet for some reason does not follow the LINE OF DEVIATION but instead changes to the LINE OF FLIGHT and ends at aa and bb and ends up making group size smaller in relation to the 50 yard group. Why?

That would mean that bullets traveling left would some how start to travel right after 50 yards, bullets traveling right would eventually travel left, bullets traveling down would then travel up and bullets traveling high would then travel down. We aren't dealing with smart bullets.

It's been about 50 years since I competed in High Power matches but I seem to remember watching through a spotting scope rounds go down range and I don't remember any of them corkscrewing and I will assume that rimfire rounds don't do that either . By my experience shooting long range silhouette matches, other than wind deflection, the horizontal flight didn't change from one range to another. Even if they did corkscrew, the amount should be a function of the twist rate and velocity. Since velocity varies from round to round one would think the amount of corkscrewing would vary from round to round. Besides, how would that explain how independently uniform the bullet would change flight.

One could speculate that the type of rifling in a barrel can effect the amount of wind deflection in both horizontal and vertical deflection and that seems to be true because minimally invasive barrels show a reduction in vertical deflection as a result of the wind.

So could the same thing happen with no wind. Does the edges of the bullet catch air and cause it to yaw sideways as it rotates. The problem with that is the deviation should always be in the same direction, not left one time and right another time. I believe it has been shown that bullets can yaw a bit and then stabilize, but again, they are already in a flight path and that shouldn't change.

I can't accept that bullets, even in a tunnel, change their flight path part way down range. If they do, there has to be an external force that causes them to do that. Either something in the tunnel or something the barrel does to the bullets to make their flight path change. In either case it isn't the ammo, it's something else and that something else should effect every brand/type of ammo used..
Have you not heard of JFK and the "magic bullet"?
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  #80  
Old 01-14-2022, 12:27 PM
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Jaia is correct on both counts

First, barrel length, within reason, isn't a factor with a scope, but a longer sight radius is a very big factor when shooting with iron sights. Barrel condition, particularly in the muzzle crown, is a much bigger factor. Leading can affect accuracy, so keeping the bore clean will help, but improper cleaning, particularly cleaning from the muzzle end with a rod or dragging a bore snake through at an angle, can do a lot of damage in a hurry.
22LR rifles are notoriously finicky about ammunition and most rifles have definite preferences that can be determined only by burning a lot of powder looking for that one they like above all others. Good ammunition with consistent muzzle velocity will help eliminate vertical stringing, but some rifles will spray expensive ammunition all over and group better on average with cheaper stuff, even with a bit of of stringing or an occasional flyer mixed in. I have a couple of older long-barreled target rifles that consistently group better with Norma TAC-22 than with Norma Target-22 at substantially higher prices. Go figure!
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  #81  
Old 01-14-2022, 01:50 PM
MManning
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It does seem bizarre that projectiles could curve, etc., during flight. But aerodynamics are a crazy thing.

One of the books by Bryan Litz ("accuracy and precision..." possibly?) discusses centerfire bullets and a test he did to prove they don't curve. They acted exactly as one would expect. Groups simply expand with distance, and the individual bullet placement stayed the same.

However I have watched air rifle pellets make a lazy spiral toward the target. There's many videos on YT showing crazy flight paths of pellets. I've also been frustrated by my field target rifle having pellets impact on one side of the POA, and the other side at a different distance in no wind conditions.

So why couldn't rimfire bullets do something similar?
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  #82  
Old 01-14-2022, 02:39 PM
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Hmmmm...do bullets curve?

Ummmm...I'm going with yeah....in multiple directions at once.

1) The vertical curve caused by gravity and time of flight.

2) The horizontal curve caused by crosswind and time of flight.

3) Random curves caused by turbulence and varying wind speeds/directions.

4) Curve caused by Magnus effect....spinning bullet and atmosphere interaction.

5) Curve caused by pitch, yaw and precession of the bullet, due to off balance bullet or asymmetry.

Combine all 5 causes, it's a wonder I can stay on paper at 200 yards.
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  #83  
Old 01-14-2022, 03:36 PM
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There's many reports of groups not maintaining shape in the Laupa test tunnels.

Why would Lapua go to the expense of equipping both of their tunnels in the US with sensors at both 50 and 100 meters otherwise? They could have saved a ton of money by only having a 50m tunnel and one sensor.

If anyone is familiar with the various BC drag curves (G1, G7, RA4 etc.), it's obvious drag is really high right smack dab where rimfire bullets fly.

Chuck Yeager was quoted after his famous supersonic flight that the transonic zone had significant buffeting. Above or below the aircraft was smooth.

Centerfire are well above this high drag area, so according to Chuck (and Bryan Litz) the flight should be smooth..

Pellets usually show the spiraling when pushed too fast and get into transonic. It's accepted that weird stuff starts happening with pellets over ~900fps so unless extensive testing is done, don't go above 870 fps or so.

I'm aware that various sources say that the transonic zone is no big deal for rimfire bullets, or bullets in general. So why did aircraft have such a hard time with it? And why is there a running joke with the centerfire long range community about the "800 yard wall" for .308 Win bullets? I've experienced that myself. 700 yard shots are almost boringly easy, and hits at 800 or more are almost impossible.

Aerodynamics is a funny thing. I've been into race car and airplanes for decades and only recently wrapped my head around what is going on with F1 cars. Aero is not intuitive.
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  #84  
Old 01-14-2022, 04:33 PM
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Why do aircraft have it so rough and 22lr not?

Shape. Short and stubby vs long and slender.

Double shockwave on the 22lr




Last edited by jaia; 01-14-2022 at 04:39 PM.
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  #85  
Old 01-14-2022, 05:55 PM
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Quote:
Originally Posted by MKnarr View Post
I will admit to not being the sharpest tool in the box but I have problems with "Some ammo shoots better groups at 100 yards than 50 yards".
Indeed. Entropy doesn't have a reverse gear.
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  #86  
Old 01-14-2022, 07:43 PM
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Aircraft have shockwaves off every significant shape change. Even in that aircraft pic with the condensation cloud, there's also one forming behind the canopy, and another on the left wing or inlet.

Classic pic of X-15 in wind tunnel with a ton of shockwaves off of every protuberance.

https://i.pinimg.com/736x/ac/3e/c3/a...eam-garden.jpg

How many lumps and bumps does a 22lr have?

In "Rimfire Revolution" by Michael R Shea, there's a section on his trip to one of the Lapua test centers. He took four rifles, and tested 18 different lots.

Most of the number are as one would expect, say .522 @ 50 and .867 @100 (still not perfect line of deviation). But there are a number of oddities.
.359 @ 50 and 1.180 @ 100. What happened to the perfect line of deviation? there's a number like this.
.823 @ 50 and .893 @ 100. Hmm. There's several like this.
1.114 @ 50 and 1.085 @ 100. Huh, what happened here?

I'm not an aerodynamicist by any stretch of the imagination, but I know that I don't know stuff. Every time I've dug into some particular aspect of aero, I come away amazed.

As has been mentioned many many times, rimfire ammo is cheap, and cheap means imperfect. So an imperfectly balanced bullet that has an imperfect shape launched with imperfect powder and primer will net imperfect flight.

I don't have an answer. But I'm not dismissing out of hand it either.
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  #87  
Old 01-14-2022, 09:44 PM
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Originally Posted by MKnarr View Post
I can't remember the guys name or book but he did a lot of work in the tunnel at the Zia gun club in Albuquerque and found there were thermals in the tunnel that affected the bullet flight. As I recall they had to cool the tunnel down to get rid of the thermals. I'm not suggesting the Lapua has issues, but even if that was the cause of the bullet weird flight, it still isn't the fault of the ammo.

As Jaia pointed out, there are a lot of external forces that can act on a bullet but so far no one has shown it's the fault of the ammo. And so far none of them can explain the smart bullet effect.
IMO at the test center ( Lapua;s) the problem is concussion bounce back from muzzle blast. the tunnel's diameter is too small, IMO it needs to be 25-ft in diameter minimum.

I based this as I shoot with CFBR shooters and when I am between 2 shooters even if I wait 15-20 seconds to shoot my RFBR rifle the shot can be disturbed from the residual effects of their rifle's muzzle blast even in an open-air environment the benches are 6-ft centered apart. I can't imagine what happens in the test tunnel.
this is Mesa's tunnel-
Ohio's tunnel- a little bit bigger but the walls are still pretty close to the muzzle. this could be why I get better results with a lot that was tested in the tunnel outside as much as 3-4mm

Lee
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  #88  
Old 01-14-2022, 10:09 PM
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Quote:
Originally Posted by MManning View Post

Aerodynamics is a funny thing. I've been into race car and airplanes for decades and only recently wrapped my head around what is going on with F1 cars. Aero is not intuitive.
Quote:
Originally Posted by jaia View Post
Why do aircraft have it so rough and 22lr not?

Shape. Short and stubby vs long and slender.

Double shockwave on the 22lr
Quote:
Originally Posted by MKnarr View Post
I can't remember the guys name or book but he did a lot of work in the tunnel at the Zia gun club in Albuquerque and found there were thermals in the tunnel that affected the bullet flight. As I recall they had to cool the tunnel down to get rid of the thermals. I'm not suggesting the Lapua has issues, but even if that was the cause of the bullet weird flight, it still isn't the fault of the ammo.

As Jaia pointed out, there are a lot of external forces that can act on a bullet but so far no one has shown it's the fault of the ammo. And so far none of them can explain the smart bullet effect.
Quote:
Originally Posted by Hi-NV Shooter View Post
IMO at the test center ( Lapua;s) the problem is concussion bounce back from muzzle blast. the tunnel's diameter is too small, IMO it needs to be 25-ft in diameter minimum.

I based this as I shoot with CFBR shooters and when I am between 2 shooters even if I wait 15-20 seconds to shoot my RFBR rifle the shot can be disturbed from the residual effects of their rifle's muzzle blast even in an open-air environment the benches are 6-ft centered apart. I can't imagine what happens in the test tunnel.
this is Mesa's tunnel-
Ohio's tunnel- a little bit bigger but the walls are still pretty close to the muzzle. this could be why I get better results with a lot that was tested in the tunnel outside as much as 3-4mm

Lee

I've snipped sections of some of these to add emphasis to certain areas. Interesting discussion and thoughts, all of them (and others as well).

But the F1 comment got me thinking about the "dirty air" and it is complex. As and F1 junkie I've reached a point of understanding that what seems logical in aerodynamic areas sometimes is not. I geek out on some of the websites where the hard core enthusiasts do CFD simulations and such, and it's crazy complex the way it all works.

And the further posts feed into that complexity even more. No matter what, that round displaces air and creates some turbulence. You can see it through a spotting scope at times. I've seen grasses swirl as a high velocity round passes close by. And to reinforce the thoughts of Hi=NV Shooter, I've heard people at some of the military sniper type training state that shooting through a lot of crossfire will disturb a trajectory. It is one of the reasons that the guys shooting precision cover will shoot from other areas.

It would almost seem to really test in depth at various ranges, it would have to be controlled to extremes, even beyond what the various test centers are doing.



And just sayin', not that I have a dog in the fight. The guys that train long distance high power and put a LOT of rounds down range... often the military guys. And they still spec longer barrels when precision is the primary focus. Some of those sniper rigs are heavy, and the military saves weight when it can as it creates more fatigue.
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  #89  
Old 01-14-2022, 10:46 PM
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https://precisionrifleblog.com/2021/...rground-range/

Reflection Off Tunnel Walls: Could the tunnel walls somehow affect the bullet’s flight? Could there be some reflection or pressure nuances that might cause the bullet to fly differently than it would in the open air? I was worried about that, so I asked a couple of ballisticians. While it might be plausible if the tunnel was very narrow (e.g., 2-foot diameter) and the bullet traveled very close to the walls, the consensus was it was unlikely that reflection off the walls could impact flight in a 3-4’ diameter tunnel for bullets traveling at the muzzle velocities typical of centerfire rifles (2,500+ fps). Dr. Vaughn wrote about this, too: “The Tunnel Range may not work for transonic velocity (1000 to 1500 fps) projectiles because the normal shock waves will be reflected back from the tunnel walls to the bullet. This can cause instability of the bullet with large dispersion. We know that it doesn’t work for low or medium large-caliber bullets such as muzzleloader or pistol bullets because we have seen oblong bullet holes in the target.”

Last edited by MManning; 01-14-2022 at 10:49 PM.
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  #90  
Old 01-15-2022, 12:12 PM
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Originally Posted by mrt949 View Post
I have a few 22 lr rifles with different barrels 16.6 18 and 24 .
Do I gain with longer or shorter when off the bench .
I shoot with scopes .
Thinning out the heard
I guess that depends on what you mean by “gain”. I’m assuming you’re not asking about accuracy; they’re your guns, so you should know which one is the most accurate. For that matter I’d think you’d have a feel for which one you shoot better off a bench.

If you have to thin the heard, keep the one(s) you like best. Better, keep them all.
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