0.177 vs 0.22 energy efficiency

[Wolverineshooter]

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?

[Rob M]

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 )

[ackuric]

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

[Wolverineshooter]

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.

[Dairyboy]

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.

[Wolverineshooter]

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.

[Rob M]

I bet someone has 2 airmax"s on the forum ,. they just need a 10 grain 22 pellet.

[ackuric]

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.

[Ribbonstone]

Want to find out?

These three all all 13.4-13.5gr. (and all JSB's)  Left to Right: .22,. 20, .177:


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?

[rsterne]

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

[Ribbonstone]

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.

[rsterne]

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

[WyoMan]

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

[rsterne]

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

[anti-squirrel]

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 

[Wolverineshooter]

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.

[KnifeMaker]

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

[anti-squirrel]

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.

[Wolverineshooter]

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.

[KnifeMaker]

The .22 will be more efficient. 

Knife