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 Posted: Thu Oct 29, 2009 4:23 pm |
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| Mark5043 |
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My Discovery is .177,and am seriously considering doing a barrel swap to make it .22.However I love the flat trajectory of the .177.My reason for doing the conversion is greater FPE.
I am looking for an answer to this question...What would have a better trajectory,.177 or .22.all other factors being equal.If I used a heavier pellet in .177,say Eunjin 16.1 gr.,and a power adjuster,it would put me in the pellet weight and velocity of the .22 version..a-little over 24 FPE.
Okay so if the pellet weight,and velocity can be made to that of the .22 version,and the pull of gravity remains constant,how would wind resistance factor into the equation.It would seem that the greater surface area of a .22 pellet would slow the pellet a-little faster,than that of the .177,all other factors being equal.So would the .177 with a pellet weight adjustment still have a flatter trajectory,than the .22...or am I missing something here?  |
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Last edited by Mark5043 on Thu Oct 29, 2009 5:57 pm; edited 1 time in total
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| Posted: Thu Oct 29, 2009 5:45 pm |
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| fritz |
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.22 pellets have a superior BC to their .177 counterparts. Both are effective hunting calibers. The heavy-slow will have a rainbow trajectory, the light-fast will have a flatter trajectory. If you had a light-slow with the same BC, they would follow similar trajectories.
I speculate the light-fast will be affected less if it can maintain velocity, because the wind has less time to impart its energy. Heavy-slow may counteract that theory by generally maintaining more velocity downrange. |
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"I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa
Speed is impressive, accuracy is deadly.
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| Posted: Thu Oct 29, 2009 6:06 pm |
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| Mark5043 |
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| fritz wrote: |
.22 pellets have a superior BC to their .177 counterparts. Both are effective hunting calibers. The heavy-slow will have a rainbow trajectory, the light-fast will have a flatter trajectory. If you had a light-slow with the same BC, they would follow similar trajectories.
I speculate the light-fast will be affected less if it can maintain velocity, because the wind has less time to impart its energy. Heavy-slow may counteract that theory by generally maintaining more velocity downrange. |
Okay thanks fritz,that makes sense.I received some input from another forum,and it was also explained to me like this........The smaller cross sectional area of the .177 cuts both ways. Less wind resistance, yes, but also less efficient from getting a push down the barrel. With the same power plant pushing .177 and .22 pellets of the same mass, the .22 pellet will be more efficient and will accelerate to a higher muzzle velocity, I believe. Therefore, if you want to get the best performance from a 14.3 grain pellet from any given air rifle power plant, you will do better with the .22.
By comparison, the same power plant pushing a lighter .177 pellet and a heavier .22 pellet will result in a greater velocity for the .177 but ultimately, less total energy transfer in terms of FPE than the same power plant pushing a .22 pellet at a lower velocity.
It is true, however, that if you can dial the power up to accelerate a heavy .177 pellet to the same muzzle velocity of a .22 pellet of the same weight, then the total FPE at the muzzle will be equal.
Hey I've learned a good lesson today! |
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Last edited by Mark5043 on Thu Oct 29, 2009 6:17 pm; edited 1 time in total
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| Posted: Thu Oct 29, 2009 6:14 pm |
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| fritz |
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| Exactly. |
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"I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa
Speed is impressive, accuracy is deadly.
It's not that I'm not a people person, it's just that I'm not a stupid people person. |
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| Posted: Thu Oct 29, 2009 9:46 pm |
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| rsterne |
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| Quote: |
| By comparison, the same power plant pushing a lighter .177 pellet and a heavier .22 pellet will result in a greater velocity for the .177 but ultimately, less total energy transfer in terms of FPE than the same power plant pushing a .22 pellet at a lower velocity. |
True statement for most guns I have had anything to do with.... you tend to get more efficiency in .22 cal than in .177.... except maybe in the lowest powered guns.... where .177 is sometimes superior.... 
One thing about PCPs, however is that they seem to be more efficient with heavier pellet weights as well in a given caliber.... My stock .22 cal Disco was 20.9 FPE with Hobbies 11.9 gr, 22.4 FPe with Exact 15.9 gr, and 23.6 FPe with Kodiak 21.6 gr pellets.... Highly modified, the effect is even more pronounced.... My latest version gets 33.8 FPE with Hobbies (supersonic), 40.9 FPE with Exact Heavy 18.0 gr, and 45.8 FPE with EunJin Dome 28.4 gr.... 
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Thu Oct 29, 2009 10:06 pm |
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| Mark5043 |
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Bob,I saw the write up you did on the Disco mods...impressive,and thorough
to say the least. 45+fpe Disco.....Good job...I bet that rifle is a real hammer! Just perfect for rats etc.  ..... ..........  |
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| Posted: Fri Oct 30, 2009 8:53 pm |
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| rsterne |
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I guess I didn't really answer your original question very well.... Trajectory (and the ability to buck a crosswind) is a combination of the muzzle velocity and the ballistics coefficient.... it is independant of caliber.... If you want a flat trajectory, use a round nose (not just domed) pellet and boot it out of the gun fast.... Weight helps too, but only because with similar shapes a heavier pellet (in a given caliber) will generally have better BC.... 
In the real world, until you get into the real high-powered stuff like a Condor.... a .177 will tend to have a flatter trajectory because most guns simply will start them out at a higher velocity.... Once the power is high enough that the .177 goes supersonic, accuracy goes away, so the ability to hit long-range targets shifts to the .22 cal.... With enough power, then you need a .25 cal, etc....
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Sat Oct 31, 2009 6:01 am |
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| broommaster2000 |
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| Posted: Tue Nov 03, 2009 4:15 am |
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| Doc Sharptail |
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| fritz wrote: |
I speculate the light-fast will be affected less if it can maintain velocity, because the wind has less time to impart its energy. |
The inverse is true- wind drift increases with velocity. I'm surprised Bob didn't catch this one. The faster your projectile goes through moving air, the more it will be deflected- regardless of weight, or b/c.
The reasoning here is that a faster projectile encounters more moving air than a slower one- basics that most rimfire target shooters are well aware of.
Regards,
Doc Sharptail |
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| Posted: Tue Nov 03, 2009 8:50 am |
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| Rogerflat |
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| But would a slower moving projectile be in the air longer, and therefore have more time to be effected by a cross wind? |
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| Posted: Tue Nov 03, 2009 10:54 am |
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| rsterne |
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| Quote: |
| The inverse is true- wind drift increases with velocity |
Sorry, but you got that wrong.... according to ChairGun, and simple physics, if you double the velocity, you will get half the horizontal deflection in a given wind speed.... Roger is correct, half the time to be deflected by the moving air is the reason.... 
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Tue Nov 03, 2009 1:42 pm |
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| Rogerflat |
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Yep. It's the same effect as gravity, in that the longer the pellet is in the air, the more gravity or a crosswind will effect the trajectory.
The reason it seems that powder burners are effected more easily by crosswinds is not because of their increased velocity. It is because of the distance to the target, which is generally much further than airgun targets. This means the bullet is in the air longer and is exposed to more crosswind. |
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I done been assisted by the trees and rivers. Never needed any minister to figure my divinity. |
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| Posted: Wed Nov 04, 2009 2:51 am |
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| Doc Sharptail |
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| rsterne wrote: |
| Quote: |
| The inverse is true- wind drift increases with velocity |
Sorry, but you got that wrong.... according to ChairGun, and simple physics, if you double the velocity, you will get half the horizontal deflection in a given wind speed.... Roger is correct, half the time to be deflected by the moving air is the reason....
Bob |
As much as I dislike dis-agreements, we're gonna hafta agree to disagree on this one. Chairgun ain't the authority that it's cracked up to be, and you're ignoring quite a bit of your own simple physics. Double your velocity, and you'll double your deflection- it has nothing to do with time, distance, or energy, and everything to do with motion of the air in wind.
It's already proven by minds much greater than mine, and I really don't have a personal stake in this, so whether I sway anyone here is of little consequence to me. I've done enough shooting in the wind to know better. Take this argument to B/R Central, and see how long you last
Regards,
Doc Sharptail |
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| Posted: Wed Nov 04, 2009 10:46 am |
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| rsterne |
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Fair enough, doc.... I'll agree to disagree with you on this one....
Here are the ballistics formulas:
| Quote: |
The wind displacement can be calculated mathematically if the information is available. The most common formula is represented by:
D = W*(T-Tv)*F
Where:
D = Bullet displacement, ft.
W = Crosswind velocity, fps
T = Time of bullet flight to target in air, sec.
Tv = Time of bullet flight to target in a vacuum, sec
F = A factor relating to the wind angle as it approaches the bullet.
The factor (F) is the sine of the angle at which the wind approaches the bullet. For example the factor for a 90 degree crosswind is 1.0 since the sine of 90 degrees is 1.0. See Table I below for other factors.
The time of flight in a vacuum is the range distance (ft.) divided by the muzzle velocity (f.p.s.). The bullet velocity remains constant in a vacuum since there is no air to slow it down. The wind velocity is usually measured in m.p.h. To convert to f.p.s. multiply by 1.467. |
Looking at this formula, we see that the deflection is directly proportional to the crosswind velocity (factors W & F).... that's pretty much a no-brainer, more wind, at more angle to the bullet flight, shoves it sideways more....
In addition, it is directly proportional to the difference in time of the bullet flight in air and in a vacuum.... The article goes on to say:
| Quote: |
The time of bullet flight in air is a little more difficult to determine unless you have a ballistic computer program to do this for you or you have access to Ingall’s ballistics tables or similar tables. Robert Rinker in his book "Understanding Firearm Ballistics" gives the following formula to estimate time of flight:
T = 2R/(Vo + Vr)
Where:
T = Time of flight, sec.
R = range, ft.
Vo = Muzzle velocity, f.p.s.
Vr = Remaining velocity at range R, f.p.s.
This formula requires only the basic information that can be obtained from either a chronograph or bullet manufacturers ballistic tables. |
This formula tells us that the bullet deflection is proportional to the range (again, a no-brainer).... and inversely proportional to the sum of the muzzle velocity and velocity at the target (what they are actually doing is using the average velocity and range).... Let's look at some examples, in every case using a 10 fps wind at 90 degrees to bullet path (ie W = 10 and F = 1.00) with the deflection converted to inches:
BC of 0.040 at 800 fps - At 50 yards, remaining velocity = 684 fps
Time in air = 2 x (3 x 50)' / (800 + 684) = 300 / 1484 = 0.202 sec.
Time in a vacuum = 150 / 800 = 0.1875 sec.
Difference = 0.202 - 0.188 = 0.0145 sec.
Deflection = (10 x 12)" x 0.0145 x 1.00 = 1.74"
BC of 0.040 at 400 fps - At 50 yards, remaining velocity = 342 fps
Time in air = 2 x 150 / (400 + 342) = 300 / 742 = 0.404 sec.
Time in a vacuum = 150 / 400 = 0.375 sec,
Difference = 0.404 - 0.375 = 0.029 sec.
Deflection = 120 x 0.029 x 1.00 = 3.48"
BC of 0.020 at 800 fps - At 50 yards, remaining velocity = 585 fps
Time in air = 2 x 150 / (800 + 585) = 300 / 1385 = 0.217 sec.
Time in a vacuum = 150 / 800 = 0.188 sec.
Difference = 0.217 - 0.1875 = 0.029 sec.
Deflection = 120 x 0.029 x 1.00 = 3.48"
BC of 0.010 at 400 fps - At 50 yards, remaining velocity = 214 fps
Time in air = 2 x 150 / (400 + 214) = 300 / 614 = 0.489 sec.
Time in a vacuum = 150 / 400 = 0.375 sec.
Difference = 0.489 - 0.375 = 0.114 sec.
Deflection = 120 x 0.114 x 1.00 = 13.68"
You can see from the above examples that doubling the Ballistics Coefficient cuts the wind deflection in half.... and also that doubling the velocity cuts the wind deflection in half.... For a given range, wind speed and direction, those are the only variables....
Bob |
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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal: Too many to count! |
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| Posted: Wed Nov 04, 2009 12:34 pm |
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| Doc Sharptail |
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| rsterne wrote: |
| For a given range, wind speed and direction, those are the only variables.... Bob |
What's missing here is pretty basic. here's a hint- motion>velocity>resistance. Long haul truckers are more familiar with these physical truths than most shooters are. Dig a little further, and you'll find it.
Regards,
Doc Sharptail |
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