My main point that a 1" grouping at 90 yards with a 12lb/ft air rifle is EXTREMELY difficult still stands.
But if you can keep a 1" grouping at 75 yards with a 12lb/ft air rifle then i still think you've earned your charities donation
cross bows your view
- Thread starter viegar0
- Start date
My main point that a 1" grouping at 90 yards with a 12lb/ft air rifle is EXTREMELY difficult still stands.
But if you can keep a 1" grouping at 75 yards with a 12lb/ft air rifle then i still think you've earned your charities donation
Its in here somewhere.
http://www.legislation.gov.uk/ukpga/1981/69/contents
Hunting with bows or xbows is indeed illegal.
Though i was always under the impression that it was made illegal due to the silent nature of the weapon, and ease with which poachers could take game unnoticed, compared to a firearm.
Sounds exactly like the sort of illogical reason our government would use. "Obviously if we make bowhunting illegal, then the poachers will stop using their bows for their illicit activities".
On topic, i have a love for all tools designed to hurl projectiles over distances, and the crossbow is no exception. I actually plan to build one myself, one day.
My main point that a 1" grouping at 90 yards with a 12lb/ft air rifle is EXTREMELY difficult still stands.
But if you can keep a 1" grouping at 75 yards with a 12lb/ft air rifle then i still think you've earned your charities donation
No old chap, you stated, as of fact, that a scope cannot be adjusted to shoot point of zero, on a 12ft lb air rifle at 75 yards. I say you are wrong.
Bet?
Or do you admit your error?
It was 75 yards but it seems the expectations of your skills exceeded that a few posts back
I think that your pulling attention from my main bone of contention here.
This is what i have a problem with.
Just done a quick calculation.
With a .22 of 16 grains
550ft/s
35 yards zero
1.6 sight over bore (inches)
and a pellet with a drag coefficient of 0.465
Bullet drop in inches:
30 yards = 0.67"
40 yards = 0.91"
50 yards = 3.67"
60 yards = 7.61"
70 yards = 12.74"
75 yards = 15.75"
80 yards = 19.06"
85 yards = 22.68"
90 yards = 26.59"
It was 75 yards but it seems the expectations of your skills exceeded that a few posts back
I think that your pulling attention from my main bone of contention here.
This is what i have a problem with.
Just done a quick calculation.
With a .22 of 16 grains
550ft/s
35 yards zero
1.6 sight over bore (inches)
and a pellet with a drag coefficient of 0.465
Bullet drop in inches:
30 yards = 0.67"
40 yards = 0.91"
50 yards = 3.67"
60 yards = 7.61"
70 yards = 12.74"
75 yards = 15.75"
80 yards = 19.06"
85 yards = 22.68"
90 yards = 26.59"
So bullet drop at 70 yards is 12.74 inches. That's definitely within the capability of most modern scopes. They might be a bit expensive for an air rifle but definitely do-able.
Indeed it is - 21 MOA. Most higher end scopes have 50- 60 MOA of adjustment these days and some double that, so even assuming no declination on the mounting, it could be dialled straight in.
I would just hoping that cbr6fs might respond to my main bone of contention - his statement that
So lets take a case in point - a Leupold VX3
http://www.leupold.com/hunting-and-shooting/products/scopes/vx-3-riflescopes/vx-3-4-5-14x50mm/
This has 120 MOA adjustment in elevation. Assuming it is centrally aligned in mounting that is 60MOA up and down.
Assuming a 1" at 100 yards working MOA equivalency 15.75" at 75 yards equates to around 21 MOA at 75 yards - less than a quarter of total adjustment and under half that available to compensate for elevation required for POI below the centre line.
As I said at the beginning, I'm not an air rifle shooter in any serious way - I prefer cartridge firing weapons, so whether HillBill can make a shot at range - I have no idea. I can be certain though that a decent scope can be zeroed for that range
Red
I would just hoping that cbr6fs might respond to my main bone of contention - his statement that
So lets take a case in point - a Leupold VX3
http://www.leupold.com/hunting-and-shooting/products/scopes/vx-3-riflescopes/vx-3-4-5-14x50mm/
This has 120 MOA adjustment in elevation. Assuming it is centrally aligned in mounting that is 60MOA up and down.
Assuming a 1" at 100 yards working MOA equivalency 15.75" at 75 yards equates to around 21 MOA at 75 yards - less than a quarter of total adjustment and under half that available to compensate for elevation required for POI below the centre line.
As I said at the beginning, I'm not an air rifle shooter in any serious way - I prefer cartridge firing weapons, so whether HillBill can make a shot at range - I have no idea. I can be certain though that a decent scope can be zeroed for that range
Red
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Apologies to the OP for taking this off topic further but...
I think the central point here for me is that, even if you have anough adjustment to bring a 12ft/lb rifle on target at 70 or even 90 yards, no responsible individual would shoot at anything living at that distance. I think that needs to be said, end of. I stop with air rifles at 40 yards and pick up a .22LR. By 90 yards I've put down the .22 and picked up a .17 HMR. Each tool has its use, and no matter who is behind it, a sub-12 airgun is no tool for 70 yard vermin control.
Now as for all the "long barrel causes the pellet to strike 4" higher". This is only true in that a longer barrel on a PCP, without changing pellet weight or the charge of air being released, will provide a higher velocity. A 12 ft/lb rifle with a short barrel will be just as accurate at a given range as a 12ft/lb rifle with a long barrel. If you swap barrels and see a rise in your fall of shot it is because you now have a higher velocity.
"It also aids long range accuracy as more spin is imparted on the pellet. " I laughed when I read this.
Google this subject if you don't believe me. - http://www.pyramydair.com/blog/2005/04/is-airgun-barrel-length-important.html
I think the central point here for me is that, even if you have anough adjustment to bring a 12ft/lb rifle on target at 70 or even 90 yards, no responsible individual would shoot at anything living at that distance. I think that needs to be said, end of. I stop with air rifles at 40 yards and pick up a .22LR. By 90 yards I've put down the .22 and picked up a .17 HMR. Each tool has its use, and no matter who is behind it, a sub-12 airgun is no tool for 70 yard vermin control.
Now as for all the "long barrel causes the pellet to strike 4" higher". This is only true in that a longer barrel on a PCP, without changing pellet weight or the charge of air being released, will provide a higher velocity. A 12 ft/lb rifle with a short barrel will be just as accurate at a given range as a 12ft/lb rifle with a long barrel. If you swap barrels and see a rise in your fall of shot it is because you now have a higher velocity.
"It also aids long range accuracy as more spin is imparted on the pellet. " I laughed when I read this.
Google this subject if you don't believe me. - http://www.pyramydair.com/blog/2005/04/is-airgun-barrel-length-important.html
It was 70, have a re-read. The 90 yards came into it where i said an air rifle was capable of dropping rabbits out to 90 yards. I was taking about the power level of a 12 ft/lb rifle at that distance, nowhere did i say i shoot at 90.
With regards to your calculations, try it again with
Accupells - 14.3 gr
610 fps ( 11.8ft/lbs)
In a long barrel rifle that strikes 4"higher than most rifles.
I don't have chairgun anymore as its not available for Mac, or i'd do it for you.
See, Huuuuuuge rifle.
With regards to your calculations, try it again with
Accupells - 14.3 gr
610 fps ( 11.8ft/lbs)
In a long barrel rifle that strikes 4"higher than most rifles.
I don't have chairgun anymore as its not available for Mac, or i'd do it for you.
See, Huuuuuuge rifle.
It was 75 yards but it seems the expectations of your skills exceeded that a few posts back
I think that your pulling attention from my main bone of contention here.
This is what i have a problem with.
Just done a quick calculation.
With a .22 of 16 grains
550ft/s
35 yards zero
1.6 sight over bore (inches)
and a pellet with a drag coefficient of 0.465
Bullet drop in inches:
30 yards = 0.67"
40 yards = 0.91"
50 yards = 3.67"
60 yards = 7.61"
70 yards = 12.74"
75 yards = 15.75"
80 yards = 19.06"
85 yards = 22.68"
90 yards = 26.59"
Funny you mention that scope Red, as that is whats been on the logun for the last 2 years. I think i've mentioned it before ages back when you posted a pic of a rifle with a Leup on it. Might be wrong though as i recall another rifle you posted with a simmons WTC on it and i could be confusing the two.
Well not exactly that scope its a VX3 3.5 -10 x50 IR. £600 of crystal clear goodness. It needed re parralaxing, but other than that its a sweet scope. The scope on the pic i posted above is a simmons, which was also more than capable of that compensation.
Well not exactly that scope its a VX3 3.5 -10 x50 IR. £600 of crystal clear goodness. It needed re parralaxing, but other than that its a sweet scope. The scope on the pic i posted above is a simmons, which was also more than capable of that compensation.
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Glad you got some amusement from it mate.
Now lets spoil it for you.
That site fails to mention differing ranges and claims both rightly and wrongly that a short barrel is as accurate as a long barrel. Well it both is and isnt, that sweeping statement may indeed be true - out to a certain range. After that it isnt.
Look at military sniper rifles. How many of those are short barrelled carbines? Wonder why none are eh? because if what you claim is true, is actually true, then a sniper rifle could be the size of an MP5 couldn't it? But as none are................
The shorter the barrel of an air rifle, the less spin is imparted on the pellet. Therefore the spin will slow down quicker and the pellet will de-stabilise in flight sooner, you will get wobble from the skirt first which will then deviate the flight path of the pellet. Greater the range, greater the deviation.
Edit to add...... if you stand 30 yards from someone with a rifle and get them to shoot a few yards to the side of you you will hear the hiss of the pellet go past. The hiss indicates good spin and stable flight. Now go back another 50 yards and do the same test. The sound will be different, more like a fluttering sound, this is due to the pellet destabilising in flight.
So why do you say its inhumane/irresponsible to shoot a rabbit at 70? Yet seem impressed by the brit and canadian snipers shooting a bloke at 2660 yards and further? I'll guarantee now that the 70 yard rabbit shot is both much easier, much more certain than the others. Also in the canadian report, he missed first shot, and shot a bag out of his hand. That impresses you does it? Humane/responsible is it? Is it ok to shoot people at stupid ranges but not rabbits at 70 yards?
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I am talking specifically about airguns here, but similar principles apply to powder burning rifles. Why does a sniper rifle not have a short barrel? Its because it needs a long barrel to make efficient use of the slower burning powders in rifle (as opposed to pistol) cartridges and to achieve the right velocity for the task in hand. This is why target rifle shooters at Bisley use very long barrels on their .308 target rifles velocity, not accuracy. It is also why my .308 Blaser has a very short barrel but is still very accurate, I have compromised velocity for an easier package to carry, but not accuracy.
A longer, heavier barrel maybe steadier to hold, soak up recoil etc etc., or provide a longer sight radius if using open sights, but it is not inherently more accurate. Another 5 secs on google - http://www.chuckhawks.com/rifle_barrel.htm scroll down to Barrel length, accuracy and ballistics.
I agree that accuracy will change at greater distances, but in a CF rifle this is principally because the projectile loses stability as it drops below the sound barrier. The long barrel target rifle is able to throw its projectiles at a higher initial velocity, so the distance at which it goes trans-sonic is extended, allowing it to maintain accuracy at a longer range. It has nothing to do with its rate of spin reducing more slowly because it spent a longer time being spun in the barrel.
A sub-12 air rifle starts subsonic, so does not have the same problem as a CF rifle at extreme range. Again, given the same starting velocity, a pellet from, for example a 18" airgun barrel is not any more stable over a given distance than a pellet from a 12" barrel, despite being 1/3 shorter. I believe that in an airgun the limit as to how short you can go will come when the air pressure needed in an extremely short barrel to reach the same velocity is such that it will start to deform pellets, but this is beyond my knowledge.
In respect of your last point, I regard it as inhumane as the margin of error is so slight that I would be radically increasing the chances of wounding if I were to attempt such shots. The morality associated with hunting animals is very different to the morality of acts conducted by soldiers in a war, someone who had served beyond the air cadets would understand this.
A longer, heavier barrel maybe steadier to hold, soak up recoil etc etc., or provide a longer sight radius if using open sights, but it is not inherently more accurate. Another 5 secs on google - http://www.chuckhawks.com/rifle_barrel.htm scroll down to Barrel length, accuracy and ballistics.
I agree that accuracy will change at greater distances, but in a CF rifle this is principally because the projectile loses stability as it drops below the sound barrier. The long barrel target rifle is able to throw its projectiles at a higher initial velocity, so the distance at which it goes trans-sonic is extended, allowing it to maintain accuracy at a longer range. It has nothing to do with its rate of spin reducing more slowly because it spent a longer time being spun in the barrel.
A sub-12 air rifle starts subsonic, so does not have the same problem as a CF rifle at extreme range. Again, given the same starting velocity, a pellet from, for example a 18" airgun barrel is not any more stable over a given distance than a pellet from a 12" barrel, despite being 1/3 shorter. I believe that in an airgun the limit as to how short you can go will come when the air pressure needed in an extremely short barrel to reach the same velocity is such that it will start to deform pellets, but this is beyond my knowledge.
In respect of your last point, I regard it as inhumane as the margin of error is so slight that I would be radically increasing the chances of wounding if I were to attempt such shots. The morality associated with hunting animals is very different to the morality of acts conducted by soldiers in a war, someone who had served beyond the air cadets would understand this.
Killing is killing mate. Morals don't come into it. If they did, no one would kill anything. What your talking about is self justification. How you justify what you are doing to yourself. Its a far greater ( not in a good way) thing to kill a person than a rabbit. If you cant accept that you are going to wound an animal at some point then you shouldnt be shooting. It happens to every hunter at some point no matter how much they try avoid it. Many will deny it thinking its bad press, but its just the reality, it happens. Every time you pull the trigger there is a chance of just wounding an animal. It could move just as you pull the trigger for example.
Are you suggesting the margin of error at 70 yards is less than the MOE at 2600 yards?
Some snippets from Wiki about rifling and spin rate.
http://en.wikipedia.org/wiki/Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.
"If an insufficient twist rate is used, the bullet will begin to yaw and then tumble; this is usually seen as "keyholing", where bullets leave elongated holes in the target as they strike at an angle. Once the bullet starts to yaw, any hope of accuracy is lost, as the bullet will begin to veer off in random directions as it precesses".
This also applies where spin has sufficiently decreased after leaving the barrel. Different pellets, different length barrels different twist rates. All effect longer range accuracy.The velocity of legal limit rifles is very low, as such the adverse effects of decreased spin happen sooner.. As i said before i will only use one rifle at that distance, because it is the ONLY air rifle i have tried that will group well at that distance. I have had maybe a dozen different rifles in the last 8 years. all of them but one wouldn't do the job. The one that does just happens to have a much longer barrel. So as to weather i can consistently group at 70, give me any of the rifles other than the logun and i would quite honestly say "no" Give me the Logun and it will group. Its not hard to be steady on target at 70 ( prone and supported). The rifle in this case is what enables me to do it. It is a tool that does that job pretty damn well.
You say the velocity of the round is what keeps it stable. by saying this
"I agree that accuracy will change at greater distances, but in a CF rifle this is principally because the projectile loses stability as it drops below the sound barrier".
I say it is the spin on the projectile which keeps it stable. So do the people who invented the rifled barrel. Though velocity and spin rate are entwined, the velocity drops the spin rate drops, but it is the spin rate that is key to stability in flight.
Are you suggesting the margin of error at 70 yards is less than the MOE at 2600 yards?
Some snippets from Wiki about rifling and spin rate.
http://en.wikipedia.org/wiki/Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis. This spin serves to gyroscopically stabilize the projectile, improving its aerodynamic stability and accuracy.
"If an insufficient twist rate is used, the bullet will begin to yaw and then tumble; this is usually seen as "keyholing", where bullets leave elongated holes in the target as they strike at an angle. Once the bullet starts to yaw, any hope of accuracy is lost, as the bullet will begin to veer off in random directions as it precesses".
This also applies where spin has sufficiently decreased after leaving the barrel. Different pellets, different length barrels different twist rates. All effect longer range accuracy.The velocity of legal limit rifles is very low, as such the adverse effects of decreased spin happen sooner.. As i said before i will only use one rifle at that distance, because it is the ONLY air rifle i have tried that will group well at that distance. I have had maybe a dozen different rifles in the last 8 years. all of them but one wouldn't do the job. The one that does just happens to have a much longer barrel. So as to weather i can consistently group at 70, give me any of the rifles other than the logun and i would quite honestly say "no" Give me the Logun and it will group. Its not hard to be steady on target at 70 ( prone and supported). The rifle in this case is what enables me to do it. It is a tool that does that job pretty damn well.
You say the velocity of the round is what keeps it stable. by saying this
"I agree that accuracy will change at greater distances, but in a CF rifle this is principally because the projectile loses stability as it drops below the sound barrier".
I say it is the spin on the projectile which keeps it stable. So do the people who invented the rifled barrel. Though velocity and spin rate are entwined, the velocity drops the spin rate drops, but it is the spin rate that is key to stability in flight.
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Just to point out this bit in the link you posted mate
"The rate of twist, expressed as one turn in so many inches (i.e. 1 in 10"), is designed to stabilize the range of bullets normally used in a particular caliber. It takes less twist to stabilize a given bullet at high velocity than at low velocity. At the same velocity in the same caliber, longer (pointed) bullets require faster twist rates than shorter (round nose) bullets of the same weight and heavier bullets require faster twist rates than lighter bullets of the same shape"
"The rate of twist, expressed as one turn in so many inches (i.e. 1 in 10"), is designed to stabilize the range of bullets normally used in a particular caliber. It takes less twist to stabilize a given bullet at high velocity than at low velocity. At the same velocity in the same caliber, longer (pointed) bullets require faster twist rates than shorter (round nose) bullets of the same weight and heavier bullets require faster twist rates than lighter bullets of the same shape"
You were comparing my belief that it is irresponsible to shoot at live quarry with a .22 legal limit air rifle at 70 yards (and up to 90?) with my attitude to the longest successful shot taken by a British sniper on Op Herrick. I am entirely comfortable with being disgusted with the former and impressed by the latter.
You are still confused.
Different pellets, different length barrels different twist rates. No, am challenging your belief that a longer barrel, all else being consistent, is more accurate than a shorter barrel, so I mean, same pellets, same twist rate, same velocity but different length barrels. If you took the barrel of your Logun, chopped it 6 and had it properly re-crowned, then carried out the necessary adjustment to the rifle to produce the same velocity with the same pellet from the shorter barrel, it would not be less accurate at any range. That extra 6 of barrel is not making the pellet twist more or faster.
You say the velocity of the round is what keeps it stable. by saying this
"I agree that accuracy will change at greater distances, but in a CF rifle this is principally because the projectile loses stability as it drops below the sound barrier".
I say it is the spin on the projectile which keeps it stable. So do the people who invented the rifled barrel. Though velocity and spin rate are entwined, the velocity drops the spin rate drops, but it is the spin rate that is key to stability in flight.
No, I said that a projectile from a centre fire rifle will lose accuracy as its velocity drops below the sound barrier as the forces involved with crossing the sound barrier in air can overcome the stability provided by its rotation (Scroll down to the transonic problem http://en.wikipedia.org/wiki/External_ballistics#The_transonic_problem). This is one of the limits on the accuracy of long range rifles, not the projectile running out of spin. A trained sniper would know this.
You are right that rifles spin projectiles to stabilise them in flight, but how does a longer barrel with the same twist rate spin a projectile more?
If you like Wikipedia then read the section here headed maximum effective small arms range http://en.wikipedia.org/wiki/External_ballistics#Maximum_effective_small_arms_range. You will note that at it mentions MV and supersonic range, but not, sadly the projectile running out of spin.
You are still confused.
Different pellets, different length barrels different twist rates. No, am challenging your belief that a longer barrel, all else being consistent, is more accurate than a shorter barrel, so I mean, same pellets, same twist rate, same velocity but different length barrels. If you took the barrel of your Logun, chopped it 6 and had it properly re-crowned, then carried out the necessary adjustment to the rifle to produce the same velocity with the same pellet from the shorter barrel, it would not be less accurate at any range. That extra 6 of barrel is not making the pellet twist more or faster.
You say the velocity of the round is what keeps it stable. by saying this
"I agree that accuracy will change at greater distances, but in a CF rifle this is principally because the projectile loses stability as it drops below the sound barrier".
I say it is the spin on the projectile which keeps it stable. So do the people who invented the rifled barrel. Though velocity and spin rate are entwined, the velocity drops the spin rate drops, but it is the spin rate that is key to stability in flight.
No, I said that a projectile from a centre fire rifle will lose accuracy as its velocity drops below the sound barrier as the forces involved with crossing the sound barrier in air can overcome the stability provided by its rotation (Scroll down to the transonic problem http://en.wikipedia.org/wiki/External_ballistics#The_transonic_problem). This is one of the limits on the accuracy of long range rifles, not the projectile running out of spin. A trained sniper would know this.
You are right that rifles spin projectiles to stabilise them in flight, but how does a longer barrel with the same twist rate spin a projectile more?
If you like Wikipedia then read the section here headed maximum effective small arms range http://en.wikipedia.org/wiki/External_ballistics#Maximum_effective_small_arms_range. You will note that at it mentions MV and supersonic range, but not, sadly the projectile running out of spin.
What are you pointing out? Do you think that your air rifle barrel would have a different twist rate if it was shorter?
I think you are misunderstanding what i'm trying to say tbh. All this time i have been talking about air rifles and you are talking about firearms for the most part.
Let me try clarify it a bit.
A blast of air from an air rifle is different to the charge used in cf cartridges. Cant compare them in terms of effect. Air has no burn time.
What i'm saying with the longer barrel is that as it gives a higher velocity, this will also give it a higher spin rate as spin is relative to velocity. The faster it flies the faster it spins. The greater the range before it slows down to destabilisation point. Were talking low velocity air rifles here, not CF rifles so get the CF stuff out of your head for a minute.
At such low velocities the destabilisation point arrives quickly. A 12 ft/lb rifle firing a pellet at a target at 70 yards for example, would only have lets say 6ft/lb of energy left so at a guess lost a third of its velocity, also a third of its spin rate. At 90 yards it will be at around 4 ft/lbs which is to say its lost half of its velocity and half its spin rate.I don't know the exact percentage required to reach de stabilisation as its different for every rifle/pellet/round combo. But at some point around that area the pellet will start to "wobble" and accuracy falls off.
Also a longer barrel delays the effects of gravity which impart forces on the pellet the second it leaves the barrel. This may only be a small amount, but at 70 yards with an air rifle the difference is a couple of inches at the POI.
A longer barrel will be more accurate at greater range than a shorter barrel on an air rifle will for the reasons above. Like i said, my other rifles wouldn't attain the same group at that distance. All had shorter barrels.
I never said a bullet will "run out of spin" i said that spin slows in relation to velocity until it reaches a destabilisation point at which a bullet will "tumble" the same thing effects air rifle pellets which aint breaking sound barriers.
Let me try clarify it a bit.
A blast of air from an air rifle is different to the charge used in cf cartridges. Cant compare them in terms of effect. Air has no burn time.
What i'm saying with the longer barrel is that as it gives a higher velocity, this will also give it a higher spin rate as spin is relative to velocity. The faster it flies the faster it spins. The greater the range before it slows down to destabilisation point. Were talking low velocity air rifles here, not CF rifles so get the CF stuff out of your head for a minute.
At such low velocities the destabilisation point arrives quickly. A 12 ft/lb rifle firing a pellet at a target at 70 yards for example, would only have lets say 6ft/lb of energy left so at a guess lost a third of its velocity, also a third of its spin rate. At 90 yards it will be at around 4 ft/lbs which is to say its lost half of its velocity and half its spin rate.I don't know the exact percentage required to reach de stabilisation as its different for every rifle/pellet/round combo. But at some point around that area the pellet will start to "wobble" and accuracy falls off.
Also a longer barrel delays the effects of gravity which impart forces on the pellet the second it leaves the barrel. This may only be a small amount, but at 70 yards with an air rifle the difference is a couple of inches at the POI.
A longer barrel will be more accurate at greater range than a shorter barrel on an air rifle will for the reasons above. Like i said, my other rifles wouldn't attain the same group at that distance. All had shorter barrels.
I never said a bullet will "run out of spin" i said that spin slows in relation to velocity until it reaches a destabilisation point at which a bullet will "tumble" the same thing effects air rifle pellets which aint breaking sound barriers.
Well shorter barrels tend to have higher twist rates in firearms. With air rifles there are various twist rates used, but i think it goes on who manufactured them.
Have a look here.
http://www.airgun.co.uk/Airgun_Accurracy.html
Without going into a bunch of theory about which twist rate is best; lets look at what works, and why it works. The object of the rifling is to rotate the pellet, and what we are really interested in, is the pellets rotation rate. To understand rotation rate, we need to look at some math. Rotation Rate = (12 / Twist Rate) * Muzzle Velocity, in feet per-second. The number 12 comes from 1 turn in a foot, or 12 inches; since we are using feet per-second. This gives our 150 grain 30 caliber rifle bullet a rotation rate of 174,000 revolutions per-minute, or 2900 revolutions per-second. Now, that’s what I call spinning!
We don't have to do this math to realize that the faster we shoot our pellet, the faster it will be rotating. While, I am going against modern ballistic theory; I will say that this theory does not have to deal with shooting the same pellet/bullet out of the same barrel at 500 FPS, and 1000 FPS. When you combine that with air gun barrel twist rates ranging from 1 turn in 20,1 turn in 18, 1 turn in 16, 1 turn in 14, and 1 turn in 12; somebody has got to be wrong somewhere!
However, since the actual rate of rotation is controlled by both velocity and twist rate; these twist rates are not really that far off the mark. However, airgun pellets have bigger problems built into their design.
And a bit more
To be real blunt, I think that a twist rate of 1 turn in 18 inches is just great for ten meter guns; but, for longer ranges, the twist rate should be at least 1 turn in 16 inches. If you only want to punch nice round holes in paper at ten meters, static and/or dynamic unbalance becomes the thing to worry about; but, as our pellet reaches further and further out. Faster twist rates mean greater pellet stability; which means greater shot to shot consistency, or accuracy. It seems that some barrel maker's think that we all shoot at ten meters, and no further..... Oddly enough one of the worlds most popular Ten Meter Match gun makers, actually use a twist rate of 1 turn in 14 inches; with out any ill effects. Go Figure! I do prefer a twist rate of 1 turn in 14 inches, for the longer pellets, like the 10.5 grain Crosman Premier, and the H&N Barracuda
Faster Twist Rates
According to Rinker's book, "Mathematics can show that both static and dynamic unbalance can be improved by a slow twist. On the other hand, the stability factor is improved by a faster twist." What Rinker appears to be saying is that while the slower twist reduces the unbalance; a faster twist increases pellet stability. Any increase in the stability factor increases consistency, which is accuracy. In other words as long as we don't go nuts with our twist rates; accuracy will be improved with a higher rate of twist. Or to be more precise a faster rate of rotation. We can increase the rotation rate by increasing our muzzle velocity; however, in the UK this can be breaking the law.
Have a look here.
http://www.airgun.co.uk/Airgun_Accurracy.html
Twist Rate
What enables this high tech boat tail bullet to be aerodynamic, and very accurate, is the rifling in the barrel, that it is designed to be shot from. These rifles usually have a fast twist rate; in fact, they have a very fast twist rate. This causes the bullet to rotate very, very fast. Without this fast rate of rotation, our high tech bullet would probably flip end over end, and it would, of course, not be worth much in the accuracy department.
Rotating our pellets, through the use of rifled barrels, helps give them stability; so, they do not flip end over end. One of the questions that we need to address, is how fast do our pellet need to spin? Airgun barrels come in twist rates from, as slow as, 1 turn in 20 inches to 1 turn in 12 inches. How do we decide which is best? And does it really matter?What enables this high tech boat tail bullet to be aerodynamic, and very accurate, is the rifling in the barrel, that it is designed to be shot from. These rifles usually have a fast twist rate; in fact, they have a very fast twist rate. This causes the bullet to rotate very, very fast. Without this fast rate of rotation, our high tech bullet would probably flip end over end, and it would, of course, not be worth much in the accuracy department.
Without going into a bunch of theory about which twist rate is best; lets look at what works, and why it works. The object of the rifling is to rotate the pellet, and what we are really interested in, is the pellets rotation rate. To understand rotation rate, we need to look at some math. Rotation Rate = (12 / Twist Rate) * Muzzle Velocity, in feet per-second. The number 12 comes from 1 turn in a foot, or 12 inches; since we are using feet per-second. This gives our 150 grain 30 caliber rifle bullet a rotation rate of 174,000 revolutions per-minute, or 2900 revolutions per-second. Now, that’s what I call spinning!
We don't have to do this math to realize that the faster we shoot our pellet, the faster it will be rotating. While, I am going against modern ballistic theory; I will say that this theory does not have to deal with shooting the same pellet/bullet out of the same barrel at 500 FPS, and 1000 FPS. When you combine that with air gun barrel twist rates ranging from 1 turn in 20,1 turn in 18, 1 turn in 16, 1 turn in 14, and 1 turn in 12; somebody has got to be wrong somewhere!
However, since the actual rate of rotation is controlled by both velocity and twist rate; these twist rates are not really that far off the mark. However, airgun pellets have bigger problems built into their design.
And a bit more
To be real blunt, I think that a twist rate of 1 turn in 18 inches is just great for ten meter guns; but, for longer ranges, the twist rate should be at least 1 turn in 16 inches. If you only want to punch nice round holes in paper at ten meters, static and/or dynamic unbalance becomes the thing to worry about; but, as our pellet reaches further and further out. Faster twist rates mean greater pellet stability; which means greater shot to shot consistency, or accuracy. It seems that some barrel maker's think that we all shoot at ten meters, and no further..... Oddly enough one of the worlds most popular Ten Meter Match gun makers, actually use a twist rate of 1 turn in 14 inches; with out any ill effects. Go Figure! I do prefer a twist rate of 1 turn in 14 inches, for the longer pellets, like the 10.5 grain Crosman Premier, and the H&N Barracuda
Faster Twist Rates
According to Rinker's book, "Mathematics can show that both static and dynamic unbalance can be improved by a slow twist. On the other hand, the stability factor is improved by a faster twist." What Rinker appears to be saying is that while the slower twist reduces the unbalance; a faster twist increases pellet stability. Any increase in the stability factor increases consistency, which is accuracy. In other words as long as we don't go nuts with our twist rates; accuracy will be improved with a higher rate of twist. Or to be more precise a faster rate of rotation. We can increase the rotation rate by increasing our muzzle velocity; however, in the UK this can be breaking the law.
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A lighter pellet can be fired at greater velocity for the same muzzle energy.
A heavier pellet will take longer (and longer barrel) to be driven up to the max velocity.
So in both cases it seems that a longer barrel will be beneficial.
HOWEVER, assuming two rifles of same muzzle energy with a particular pellet weight, the muzzle velocity must be the same, hence (assuming same rifling) the pellets will have same spin rpm.
I believer (but am no expert) that with firearms one benefit of a *much* longer barrel is less turbulence around the projectile from propellant gases (reduced pressure and velocity of gases) as the projectile exits the barrel.
A heavier pellet will take longer (and longer barrel) to be driven up to the max velocity.
So in both cases it seems that a longer barrel will be beneficial.
HOWEVER, assuming two rifles of same muzzle energy with a particular pellet weight, the muzzle velocity must be the same, hence (assuming same rifling) the pellets will have same spin rpm.
I believer (but am no expert) that with firearms one benefit of a *much* longer barrel is less turbulence around the projectile from propellant gases (reduced pressure and velocity of gases) as the projectile exits the barrel.
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