GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Wolverineshooter on September 26, 2017, 06:44:27 PM
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Airmax MKii (aka PP700) have two versions, 0.177 and 0.22. My understanding is that they were the same except the barrels. If we were to set the two pistols the same way so each shot the air released are the same. If we use pellets of the same weight, which would have a higher muzzle speed?
My hypothesis is that the 0.177 will be faster. My rational is that with the smaller bore in 0.177, the air will move faster and therefore the energy transfer will be more quickly. Given the short barrel length of pistols that would mean a faster shot for 0.177.
Therefore, 0.177 will be more efficient, am I right?
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in fpe , the 22 is more efficient regardless of weight.. If the 2 were the same weight , a 10 grain 22 and a 10 grain 177 in the gun , I suspect the speed would be the same from the same length barrel.. Lets wait on the airgun scientists to chime in ( in theory , the 177 should be faster , but in a practical test I think the difference in speed would be negligible )
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The main difference here is area of the bore / pellet which in a .177 vs a .22 the .22 has an advantage allowing more air to pass / more pressure at the rear of the projectile. At the end of the day a 10 gr .22 cal should always make more power than a 10 gr .177.
A .177 pellet has 54~ lbs of force @ 2000 psi pushing along the projectile.
A .22 pellet has 81~ lbs of force @ 2000 psi pushing along the projectile.
-Matt
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The main difference here is area of the bore / pellet which in a .177 vs a .22 the .22 has an advantage allowing more air to pass / more pressure at the rear of the projectile. At the end of the day a 10 gr .22 cal should always make more power than a 10 gr .177.
-Matt
That is one part of the equation, that more air particles pushes in the bigger bore. But the air has to go somewhere so I still think the air should move faster, so we have both plus and minus. We really need some scientists to work this out, or some one with both barrels to try out. Just curious.
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What others have said your thinking is actually opposite. Takes less air for a 10gr .22 to shoot at let's just pick 800fps than a 10gr .177 at 800fps.
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What others have said your thinking is actually opposite. Takes less air for a 10gr .22 to shoot at let's just pick 800fps than a 10gr .177 at 800fps.
I understand my thinking is opposite. However I am not yet convinced.
In break barrels you seem to be right, rifles listed with the same breaking force the 0.22 listed with higher fpe.
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I bet someone has 2 airmax"s on the forum ,. they just need a 10 grain 22 pellet.
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What others have said your thinking is actually opposite. Takes less air for a 10gr .22 to shoot at let's just pick 800fps than a 10gr .177 at 800fps.
I understand my thinking is opposite. However I am not yet convinced.
In break barrels you seem to be right, rifles listed with the same breaking force the 0.22 listed with higher fpe.
Sorry friend, you cannot defy physics...I clearly laid out the math of how pressure works. Pounds per square inch...the more area you have available, the more energy that can be delivered when using the same pressure and weight projectile...in the smaller diameter bores the air creates a wall the size of the bore and pushes itself creating a 'line' or pressure 'waves' if you will...the line (of pressure) just becomes longer in a .177 with more wasted air after the projectile leaves the barrel when compared to an equal weighted projectile in a bigger bore...
A .177 pellet has 54~ lbs of force @ 2000 psi pushing along the projectile.
A .22 pellet has 81~ lbs of force @ 2000 psi pushing along the projectile.
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Want to find out?
These three all all 13.4-13.5gr. (and all JSB's) Left to Right: .22,. 20, .177:
(http://i157.photobucket.com/albums/t50/ribbonstone/micro%20pellets/WIN_20151219_11_33_08_Pro.jpg) (http://s157.photobucket.com/user/ribbonstone/media/micro%20pellets/WIN_20151219_11_33_08_Pro.jpg.html)
If you like heavy and fast, JSB offers a 25gr.(ish) .22 and a 25gr. (ish) .25 as well as a .22 and .25 pair at 25gr.
Or you could go with 21gr (ish) and find a .177, 22, and .25 at about that weight to terst side by side.
BUt basically you are right. Give then same nosse and edge profile, the long skinny pellets have a better BC (And SD) that the same WEIGHT pellets of larger calibers.
So...is there really a surpise that long and skinny "cuts" though the air bigger than short and fat?
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If you have two identical PCPs, one in .177 cal and the other in .22 cal, operating at the same pressure, the .22 cal will produce more FPE, period.... That is because the force on the .22 pellet is 54% greater, so if the barrel length is the same, you would have the POTENTIAL for 54% more FPE.... Now if the gun is tuned for low power, with the valve closing very early in the pellet travel in the barrel, the .177 can gain back some of those losses, but nowhere near all of them....
If the pellet weight is the same, then the larger base area of the larger caliber provides more force to accelerate the pellet, so the muzzle velocity will be greater in .22 cal than in .177 cal.... However, most .22 cal pellets are heavier than .177, which evens out the velocities somewhat, but then the heavier pellet ends up with more FPE....
Your argument about the "air moving faster" in the smaller barrel would only apply with NO pellet loaded.... The air cannot move any faster than the pellet, and in fact only the air immediately behind the pellet is moving at pellet velocity.... At the breech end, while the valve is open, the air is simply expanding out of the reservoir to fill the barrel as the pellet moves away from the breech.... After the valve closes, the air in the barrel is simply expanding, so the air at the breech, on average, is stationary.... because the air molecules are simply vibrating at about 1650 fps in random directions....
Once the pellet exits the barrel, for a given weight, the .177 pellet will, generally, slow down less as it travels downrange.... but that is a completely separate argument....
Bob
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Didn't take the question that way...was looking at the same launve speed/same weight between diffeent calibers.
Yep...it's easier to get the same launch speed (lets you the example of the 13.4-13.5gr. pellet pitrued above as an example as we all like a "visualt reference").
But I'm going to stick to the same weight pellets (n ithis case 13.4-13.5gr.)
It's the "SI" in "PSI"..square inches.
So smack a pellet with 3K pressure at firing. A .18" pellet has about .035 square inches..so it starts off with a 24.3 pounds force pushing on the base at the start. . A .20 cal. ends up with 30 pounds of force on the pellet base. A .22 ends with 36.3 pounds of fice on the pellet base. A .25 ends up with 46.9 pounds of force pushing on the pellet base.
Yeah...you can control the final energy by adjusting HOW LONG that pressure is applied (the valve dwell and ability to deliver air though the varsious restrictive holes between pellet and air sourse), but it will work for a comparsion.
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Ribbon, your force numbers are off by a factor of PI, so less than 1/3 of the actual values.... but the ratios are correct.... A .25 cal pellet has 147 lbs. accelerating it at 3000 psi....
Bob
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I think it's important (in this kind of comparison) to look at barrel volume as the driving factor... i.e. two different barrels, same weight projectile, same firing charge - the barrel with the larger volume wins the fpe race.... and the velocity race (for the same weight pellet).
It's harder and sometimes impractical to get the smaller calibers up to the same barrel volume.
Wyo
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Gary, you are 100% correct.... The Maximum FPE calculation can be simplified down to barrel volume and pressure.... providing the "firing charge" is large enough.... If the firing charge is really tiny, of course, and you try too large a barrel volume, this may not apply.... eg. if you put a 1" bore barrel 10 feet long on a .177 pistol that only shot 5 FPE.... the bullet may not even get to the end of the barrel before friction overcomes the falling pressure....
Bob
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I tested this using my 2240 using 15 grain Sniper Magnums in .177 and 15.4 grain Gamo Redfires in .22. Swapped barrels out in one session and still surrpised over the validation. The .22s were a hair faster, 540 FPS versus 535 FPS. I was impressed, so I then compared 13.1 grain Skenco New Boys in .177 to 13.4 grain JSB Exact RS domes in .22. 545 in .22 versus 540 in .177. Yes, I know the pellets aren't the exact same weight, but close enough for my very unscientific test.
The math is what I trust implicitly, as we had to work out stuff like this when I was in Nuke Power School. I don't miss doing those equations, but the lesson stuck, and Bob, Gary, and Ribbs are on the money.
For ease of testing the 2240 is a near ideal platform as barrels are dirt cheap and CO2 is sorta self-regulated. And my testing also confirmed what Bob says where if I want more oomph outta my 2240 as a 1740, then I need a longer barrel. I now have a 24" barrel (though I admit it looks silly as a pistol with a 24" barrel!).
Side note: maybe that's where all my CO2 powerlets have gone?
Second side note: how is it people strip out those breech screws? I file my hex keys flat so they fit precise, ya know. Nary a problem :D
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Thanks a lot guys , interesting, isn't? I agree the barrel volume is a determining factor, the smaller but longer barrel may have advantage. But in the case of pp700 the two barrels are same length so 22 will have more volume and more energy. But interesting to see the difference are not much.
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In the title, the op ask about a comparison in efficiency. However, once the post began, he switched it to fps. This is a typical mistake, and the one typically used by lesser quality ag manufactures to lure unknowing customers to their high fps airguns. With the newbies Never knowing that fps in not necessarily fpe, or efficiency.
How many times have we seen a proud new owner of a breakbarrel think his 1200-1500 fpe .177 shooting feather weight pellets was the more powerful ag that a larger cal shooting at a much lower fps. (I won't even go into the part that the high fps is useless as far as hitting a target at any decent range.
So many equate fps with efficiency. It is simply not the case. Not unless we are talking the same bore size/projectile weight/bc.
Apples and oranges here Folks. With many manufacturers selling them as peaches. LOL!!
Knife
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In the title, the op ask about a comparison in efficiency. However, once the post began, he switched it to fps. This is a typical mistake, and the one typically used by lesser quality ag manufactures to lure unknowing customers to their high fps airguns. With the newbies Never knowing that fps in not necessarily fpe, or efficiency.
How many times have we seen a proud new owner of a breakbarrel think his 1200-1500 fpe .177 shooting feather weight pellets was the more powerful ag that a larger cal shooting at a much lower fps. (I won't even go into the part that the high fps is useless as far as hitting a target at any decent range.
So many equate fps with efficiency. It is simply not the case. Not unless we are talking the same bore size/projectile weight/bc.
Apples and oranges here Folks. With many manufacturers selling them as peaches. LOL!!
Knife
and it makes us bananas!
Like in archery, I prefer a slower but heavier projectile. Maybe I'm crazy. Or perhaps I lost my grapes.
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I assumed the pellets to have the same weight to simplify the discussion. When different weights are used in the same gun, the efficiency will be different. So the question is still about efficiency, at least that is what's in my mind.
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The .22 will be more efficient. ;)
Knife
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You're original question was about FPE, since you mention velocity of the the same weight pellet of different calibers. There has been a lot of discussion about the air behind the pellet. But what about the air in front of the pellet? Unless you are shooting at something right in front of the barrel you must take into account the effeciency of the projectile with a smaller surface area and the same weight t(and same velocity) raveling through the air for a 100 yards. Two projectiles with same weight but different surface areas will reach terminal velocity differently. The thinner more torpedo like projectile should retain higher velocity at farther distances.
I do not have any scientific results but my .22 galatian shooting a 25 grain pellet at 860fps seems to have less arc than the same .25 pellet in 25 grains traveling at the same 860fps out to 109 yards.
I hope I'm not going off from the original discussion but it's something I often think about.
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You guys are all amazing! Thanks Rob, Matt, Dillon, Ribbonstone, Bob, Gary, Peter, Michael Stephne.
I found the following article that I think addresses the problem. In terms of my argument for a faster “speed of air” for small bore (which really should be higher pressure in a small bore due to smaller volume), the article showed that it is not enough to overcome the larger force due to big contact surface with the air. Here is the link: http://www.kiledjian.elac.org/phys%20001/Ballistics%20of%20Air%20Gun.pdf. (http://www.kiledjian.elac.org/phys%20001/Ballistics%20of%20Air%20Gun.pdf.)
From this article I can conclude:
1. For the same gun, you will have the same muzzle energy regardless of the pellet weight, as long as the friction between the pellet and the barrel are the same.
__ This is counter-intuitive to me, I thought the heavier pellet would have a little advantage. I would imagine the heavier pellet would have a higher friction, so based on this article, will have even less muzzle energy than a lighter pellet.
2. Bigger bore will yield more muzzle energy provided the guns are the same except the bore size.
___It is not clear to me if a bigger pellet will have more friction or less friction. I would bet on the more side.
3. Bigger bore requires longer barrel to achieve optimal muzzle energy
4. When barrel length are optimized, in guns with very low friction, the big bore will have more muzzle energy. When friction is above certain threshold the smaller bore will have more muzzle energy.
So whatever the gun you have, make sure the barrel has minimal friction (really straight and uniform, no burs), and your pellets are symmetric, uniform in skirt and really smooth to minimize the friction! Many people use moly on their bullets for lubrication to minimize friction, that should help.
5. The time the pellet travel in the barrel is very shot (on the scale of <1/300 seconds scale), any air released after that time is a waste. So for PCPs we should have maximum openings in the air holes but use a weaker spring to keep the volume of the air up but shortening the time to maximize efficiency
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You're original question was about FPE, since you mention velocity of the the same weight pellet of different calibers. There has been a lot of discussion about the air behind the pellet. But what about the air in front of the pellet? Unless you are shooting at something right in front of the barrel you must take into account the effeciency of the projectile with a smaller surface area and the same weight t(and same velocity) raveling through the air for a 100 yards. Two projectiles with same weight but different surface areas will reach terminal velocity differently. The thinner more torpedo like projectile should retain higher velocity at farther distances.
I do not have any scientific results but my .22 galatian shooting a 25 grain pellet at 860fps seems to have less arc than the same .25 pellet in 25 grains traveling at the same 860fps out to 109 yards.
I hope I'm not going off from the original discussion but it's something I often think about.
Your question is discussed in another thread: https://www.gatewaytoairguns.org/GTA/index.php?topic=132886.msg1320722#msg1320722 (https://www.gatewaytoairguns.org/GTA/index.php?topic=132886.msg1320722#msg1320722)
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I'll just throw a general idea out there that I try to live by. I've found that if I can get good-to-great accuracy at the distances I'm intending to shoot with a heavier pellet in a given caliber, that is what I stick with.
A good example is the H&N Sniper Magnums in .177- 15.1 grains. These pellets seem to do better as power levels increase, but even when I adjust for shot count in my PP700 (shooting ~ 550 FPS) they group extremely well. I have taken several squirrel at lower velocities with these specifically because at the shorter ranges I'm using them (< 20 yards for pesting generally) I can put them wherever I want with precision- meaning into the ear from side shots or eye from frontal shots. Crow Magnums are not as accurate across all my airguns, but their weight also merits exploring for those who prefer heavier-weight pellets... and heavier pellets in general maintain their energy levels in a given caliber.
Or to summarize, I like the heaviest pellet that afford good accuracy. A small loss in velocity is worth it if I can maintain more precision, especially as distances increase. But this also requires more bench-time learning not just the gun but the way the pellet behaves.
Disclaimer: My choice is also influenced by my fast accumulation of Choice Hotel points converted to Amazon gift cards and thus getting H&N pellets "for free". I generally avoid ordering over pellets on Amazon, but H&N arrive in perfect condition thanks to a somewhat sturdier tin with a screen-on lid.
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Peter, agree with you.
Within the caliber, heavier pellet tend to have better BC, and heavier weight makes them more stable (resistance to wind for example), so it will fly more true and deliver more bang. Of course the drawback is the shot will curve more and could be difficult for long distance shot.
Between caliber, things are a little different. larger caliber will have more muzzle energy to start with (assuming same gun except different barrel). But smaller bore pellets of the same weight will have better BC and preserve more energy, which could make the smaller bore a better choice for the longer range.
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Unfortunately, there is a lot of guesswork and opinion in this thread, that is taking it in a direction different to what actually happens.... In PRACTICAL terms, larger calibers shoot heavier pellets, and in fact the SD of "normal" or similar pellets INCREASES in proportion to caliber, and therefore so does their ability to carry energy downrange, or to buck the wind.... So, although there are obvious limits (you can't put a .50 cal barrel on a .177 pistol and expect reasonable performance).... generally speaking, in one given gun, the larger of two calibers will have more hitting power (FPE), and less wind drift.... but the smaller caliber will have a flatter trajectory and greater penetration....
Bob
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This is kind complicated, especially in terms of resistance and stability. So some actual experiment would be helpful.
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Test conducted with a modified 2250, comparing a .25 cal barrel and 25.4 gr. pellets (SD = 0.058) to a .30 cal barrel and 44.8 gr. pellets (SD = 0.071).... Both barrels were 25" long, and the power source was a single 12 gr. CO2 cartridge.... The same port sizes and valve volume were used for both tests, the ONLY change was the caliber and pellet.... Note that if you scale the 25.4 gr. JSB up to .30 cal, it would have a weight of 43.9 gr.... so the relative SD of the 44.8 gr. pellet shows a nearly perfect correlation to the expected SD increase being proportional to caliber.... ie the pellets are nearly identical in shape, and hence FF.... This will give the advantage in BC to the larger caliber, in just about exactly the ratio of (.30 / .25) = 1.2, as would be expected.... I used a BC of 0.039 for the .25 cal and 0.047 for the .30 cal in the calculations, although the BC of the 44.8 gr. JSB Exact .30 cal is actually a bit higher than that....
.25 cal.... 23 shots above 300 fps
594
600
593
585
571
559
560
553
547
540
542
533
539
529
526
518
514
519
509
492
452
408
360
Average velocity 528 fps.... Average energy 15.9 FPE.... Total energy per cartridge 366 FPE.... Efficiency in .25 cal is 0.88 FPE/CI....
.30 cal.... 20 shots above 300 fps
468
468
469
462
467
464
461
466
458
463
467
466
464
462
460
458
442
408
369
327
Average velocity 446 fps.... Average energy 20.1 FPE.... Total energy per cartridge 403 FPE.... Efficiency in .30 cal is 0.97 FPE/CI....
Since the SD of the .30 cal pellet is higher than the .25 cal, and the shape is nearly identical (both are JSB Exact).... the .30 cal pellet is not only starting with a 26% advantage in FPE, it will lose less velocity and energy as it goes downrange.... At 50 yards, the .25 cal pellet will have about 11.6 FPE remaining, while the .30 cal will have about 15.3 FPE.... an advantage of 32% at the target in favour of the larger caliber....
This is just one example of what happens in the real world, using typical pellets for the caliber, and the same gun, same power source, same barrel length, just a different caliber, shooting a normal pellet.... I hope that helps convey my point....
Bob
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excellent demo bob , I enjoyed looking through the numbers !