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Hi to everyone - I am brand new to RFC and this is my first post. I have two questions. 1st. - Most makers of .22lr rf ammo produce 4 velocity ranges, subsonic, standard, high and hyper. Does each velocity use the same type of powder, just increasing amounts, or is a different powder used to achieve the desired velocity? 2nd. - If it is generall accepted that a 16" barrel is both legal and produces the fastest velocity, why on guns w/o iron sights (thus requiring a scope) are barrels longer than 16"? Just wondering. Thanks for any information. Sam Levitt
 

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Chief says : Different manufacturers of ammo use different
powders as well as different powders in certain cartridges.
per thier bullet weights vrs velocity required.

Barrel length - One might obtain the hishest velocity from a 16
inch barrel , but not the ultimate accuracy for the gun it is installed on. Many opt for the 18 inch barrel. for no dought
a std length above the legal limit. Balance plays a part also.

PLUS in the 22 magnum : atleast an 18" barrel is required for
optimum performance.

CD.
 

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Sam,
best accuracy is not always attained by highest possible velocity, particularly with a bullet that passes the sound barrier on the way to the target. In .22lr most achieve best accuracy when the bullet exits the barrel below the speed of sound.
Take care,
warren
 

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Sam:

Because powder used by the manufacturers is proprietary, you would probably have to bribe a chemist or ballistics engineer to get that information. As I understand it, powders used for their factory loads are not standardized. Powders released for handloading MUST be standardized. The amount of powder from a particular lot used for factory loads, will be determined by it’s burning rate.

As to your second question: The way you phrased the question suggests that you understand the reason for longer barrels with iron sights.

Why use a barrel longer that 16 inches, with a scope, when maximum velocity is achieved at that barrel length? The answer is based on bullet stability and the speed of sound.

With a long barrel, the bullet starts to slow down after 16 inches and will exit the barrel with less muzzle blast.

Velocities of the .22 rimfire are within the range of the speed of sound. In a short barrel, most rimffire ammo will exceed the speed of sound in the barrel. If the bullet drops down below the speed of sound before it reaches it’s target. it will be “jerked around” in that transonic zone, and will probably be diverted from it’s true course.

If we can keep Hi-Speed and Hyper Velocity ammo well above the speed or sound on it’s way to it’s target, we should expect better accuracy than if it slips into that area where the speed of sound buffets it, before it gets to the target.

With standard velocity rimfire stuff, you might find that because the bullets have a range of velocities, some bullets will be above and some below the speed off sound. When you hear that “crack”, you know that one went supersonic.


So: Barrel length, bullet speed and the speed of sound all have an influence on what your barrel “likes”.


Just to add a little more s**t to the complicate things: The speed of sound changes as the temperature changes. Sound travels faster in hot weather and slower in cold weather.

Fun Huh: As Obx22 sez: "In .22lr most achieve best accuracy when the bullet exits the barrel below the speed of sound."

Joe Haller
 

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Think of it this way...

The burning powder forms gasses which expand to propel the projectile (bullet) down the path of least resistance (the bore) toward the muzzle at an ever-increasing speed. At the same time, the bore acts to contain the bullet while the rifling grooves (normally 1 turn in 16 inches for .22LR) impart a spin to stabilize the bullet in flight.

All the while this is happening, the friction from the lands and grooves is acting to slow down the bullet. In a .22LR, at a particular point (generally approx. 16 inches), the expanding gasses have probably reached their maximum ability to increase the velocity of the bullet. Beyond that point, additional barrel length creates drag which acts to slow down the bullet.

However, depending on the weight and configuration of the bullet, and powder burn rate, 16 inches may not be the optimal length to best stabilize the bullet for a target at a specific distance. And, while all this is going on, barrel harmonics (vibration) is also taking place. That and other qualitative factors muzzle crown, bore smoothness, bore/chamber concentricity, etc., etc. are why one rifle "likes" a particular ammo and another rifle won't particularly shoot well with it.

Since we can't "handload" rimfire ammo like we can centerfire, we just experiment with different brands and types until we find least expensive ammo that works best in our rifle for the purpose we have in mind. :cool:
 

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Aw, heck, I may as well chime in here...

Every couple of years or so, a gunwriter or two writes and article on Barrel Length vs. Muzzle Velocity. The trouble is, I have yet to see one with decent enough methodology to make the endeavor worthwhile, and even then, it is a near thing.

Do do it right, we need two ~pistols~ : A semi-auto and a bolt action: start them out with identical make bore and twist dimension barrels 26" long or longer, and have them chambered identically: run five 10-shot strings for velocity with about five or six common ammunition types, then trim and crown the barrels back 1 inch exactly and repeat until you stop at 2" or 3".

You will be expending no less than 1250 rounds of ammunition assuming five ammunition types. That's a lot of data to compile parse and present.

With known quantities such as barrel and chamber dimensions, you would have a fairly accurate baseline. It would be a bother to go through it all and stay sane. I volunteer to do the shooting though...
 
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