0.177 vs 0.22 pellets, if the same weight and shape

[Wolverineshooter]

I am wondering when the pellets have the same shape and weight, if 0.177 should have less air resistance (higher BC) than 0.22. 0.177 may also have a more stable flight. My reasoning is that there is less collision with air molecules with 0.177 due to smaller surface area than 0.22. Am I right?

[rsterne]

Essentially correct.... There are two factors in pellet drag, the Form Factor (FF) and the Sectional Density (SD).... The SD can be thought of as the "weight per square inch of bore area", in other words it's ability to maintain velocity against the air resistance.... SD is calculated from....

SD = Weight (grains) / 7000 / Caliber (inches) ^2 .... The 7000 changes the weight in grains to lbs....

The Ballistics Coefficeint (BC) is found from....

BC = SD / FF .... If the shape is identical, then so is the FF.... Wadcutters have more drag, so a high FF.... Round Nosed pellets have less drag, so a low FF....

If the weight is constant, then the SD is higher in the smaller caliber.... For a 10 gr. pellet....

SD (.177 cal) = 10 / 7000 / (0.177 ^2) = 0.046

SD (.22 cal) = 10 / 7000 / (0.22 ^2) = 0.030

Round Nosed pellets tend to have a FF of about 1.5, and IF the two pellets in question had the same FF....

BC (.177 cal) = 0.046 / 1.5 = 0.031

BC (.22 cal) = 0.031 / 1.5 = 0.021

In fact the .22 cal pellet would tend to be shorter and fatter in proportion, so the FF would likely be greater, dropping the BC even lower than this calculated value.... If the FF of the .22 cal, 10 gr. pellet was 2.0, the BC would be about 0.016....

Bob

[grand-galop]

I saw a video of Steve Shally revisiting the power and shootability of .177 cal..  It was educational for me because of what I was reading in some forums was definitely going with .22 cal.  If you can tune a rifle to shoot a .177 cal at 10.2g or greater past the 800 mark, the pellet carry enouf energy to drop a small game for sure if you do your part..Here is the link to the video..

[Mod90]

Bob beat me to it, and at it. Excellent explanation by rsterne.
But I'll add a little something to the topic.

A 16 grain .177 diabolo pellet will be a bit longer than a 16 grain diabolo .22, & that little longer length can have a negative effect on stability, depending on the twist rate of both barrels & on how fast they are going when they leave the muzzle.This can negatively affect the pellet's stability in flight.

[rsterne]

A .177 pellet will require a faster twist rate than a .22 cal, even for the same length pellet.... Twist rates are calculated in calibers, and then converted to inches.... You need twice as fast a twist (in inches) in a .177 cal than in a .357 cal for the same bullet proportions....

Bob

[Wolverineshooter]

Thanks Bob and Ricky for the excellent explanations. As for the twist rate, I assume the gun manufacturer has done the job properly, creating the twist rates based on the calibre.

So for pellets of the same weight and started with the same speed, the 0.22 pellets will have more wind drag and therefore will deliver less hit, but 0.177 may be less stable if it is longer.

[Wolverineshooter]

Thanks Alain. That Daystate Wolverine is amazing!

0.177 will have advantage in terms hitting power compared to a 0.22 pellet of same weight and starting with the same speed due to less wind drag. But may be less stable if it is longer. From this video 0.177 appears to be still very accurate. Very informative!

[Wolverineshooter]

Let's say the pellets weigh 15gr, with muzzle speed 700fps, 0.22 BC=0.016, 0.177 BC = 0.031 as in the case Bob calculated. Then the energy will be:

Yards   0.22 energy    0.177 energy
0          16.32              16.32
10        14.05              15.10
25        11.29              13.47
50        7.86                11.16
100       3.7                 7.7       

So 0.177 will have more killing power at a longer distance.


What it takes for the 0.22 to match the killing power of the 0.177? Let's increase the speed for the 0.22 to match the killing power of 0.177:

0.22 Muzzle speed    Muzzle power     Distance   Hitting power
700                          16.32                0              16.32
727                          17.60                10             15.10
768                          19.64                25             13.47
852                          24.17                50             11.16
1170                         45.59                100             7.7

So if your goal is short distance hunting, then 0.22 may do better if it has more power to begin with. But 0.177 will have advantage in the long distance that 0.22's higher initial energy may not be sufficient to compensate.

Did you see that it requires 46fpe for 0.22 to match the killing power at 100 yards of 0.177 with a muzzle power of 16.32? just because of less drag in 0.177.

The pellet makers should publish the BCs to help us with  the choice of pellets.

[skorec]

Thanks all for excellent  explanation.
Unfortunately  extra heavy .177 pellets  are unstable  by using  standard  barrels.
I am thinking  that caliber .133 will be the future.

[Wolverineshooter]

Thanks all for excellent  explanation.
Unfortunately  extra heavy .177 pellets  are unstable  by using  standard  barrels.
I am thinking  that caliber .133 will be the future.

Based on Bob's explanation, the twist rate of the gun is based on the caliber. So beyond caliber, other factors affecting the stability would be the length of the pellet due to more contact to the air. Not sure how much impact this will have. The surface area on the side of the pellet is proportional to its length, as well as its radius. So does this mean two pellets with the same shape and length but different radius, the fatter one will be less stable?

[rsterne]

There seems to be quite a bit of confusion in this thread about bullet stability.... Perhaps by using the Kolbe Twist Calculator you could answer many of your own questions....

http://www.geoffrey-kolbe.com/barrel_twist.htm

As far as comparing pellets of equal weight in different calibers, that is really not practical, for the same gun will NOT launch the smaller pellet as fast.... or alternately it will launch a heavier, larger caliber pellet at the same velocity.... While your numbers comparing equal weight pellets is interesting, it is not really practical, nor does it apply to a gun having the barrel changed between .177 and .22 cal in the real world.... It is sometimes easy to lose sight of the forest for the trees.... Generally, when a gun is made in two different calibers, shooting "normal" ammunition for that gun.... the larger caliber will provide more FPE and hence more "killing power" downrange.... The drawback is that it will not have as flat a trajectory as the smaller caliber....

Bob

[K.O.]

Thanks all for excellent  explanation.
Unfortunately  extra heavy .177 pellets  are unstable  by using  standard  barrels.
I am thinking  that caliber .133 will be the future.

My BSA Buc loves the 15g Sniper Magnums... I am pretty sure all BSA barrels are  1:19 twist... Pellets make their own rules as far as twist... they need very little in comparison to slugs/bullets...

then there are foster slugs that do well in the right smooth bore and they spin very slowly also...

Pellets  because they come in different head shapes, waist configuration etc in the end will like what they like at different velocities...

[Wolverineshooter]

There seems to be quite a bit of confusion in this thread about bullet stability.... Perhaps by using the Kolbe Twist Calculator you could answer many of your own questions....

http://www.geoffrey-kolbe.com/barrel_twist.htm

As far as comparing pellets of equal weight in different calibers, that is really not practical, for the same gun will NOT launch the smaller pellet as fast.... or alternately it will launch a heavier, larger caliber pellet at the same velocity.... While your numbers comparing equal weight pellets is interesting, it is not really practical, nor does it apply to a gun having the barrel changed between .177 and .22 cal in the real world.... It is sometimes easy to lose sight of the forest for the trees.... Generally, when a gun is made in two different calibers, shooting "normal" ammunition for that gun.... the larger caliber will provide more FPE and hence more "killing power" downrange.... The drawback is that it will not have as flat a trajectory as the smaller caliber....

Bob

Based on the anti-squirrel's casual experiment in the other thread, https://www.gatewaytoairguns.org/GTA/index.php?topic=132889.0, which I quote below:

*********************
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 
***************************

What I am seeing here even though the 0.22 is faster and have more muzzle energy, but by not much. So BC will be a more dominant factor in the performance.

[rsterne]

Yes, in anti-squirrel's tests, the velocities were close, although he didn't state if the barrels were the same length in both calibers.... A common .177 cal conversion on the 2240 (which has a 7.5" barrel) is to use the 10.1" barrel from a 1377.... My personal experience, using the same barrel length in different calibers, shows a much larger difference in FPE in favour of the larger caliber, when all other factors are kept the same....

The very title of this thread is problematic.... If a .177 and a .22 cal pellet are the same weight, they will NOT be the same shape....

Bob

[AlanMcD]

Bob - I agree, as that is the first thing I thought of when I read the title and first post . . .

Greg,
You have created an unrealistic specific set of defined conditions intended to be able to effectively reach a conclusion that you seem to want to reach. I am not sure why . . .

Especially in the world of PCPs (which is what this forum is targeted at), you are never going to find a situation where you will be able to put more power downrange with a .177 than you can with a .22 unless you intentionally "handicap" the .22 with a sub-optimal set of conditions or tune.  That is exactly what you did in your hypothetical question in this thread - as evidenced by having to have the gun that shoots the two pellets at the same speed be uniquely tuned to use less air for the .22 to get to that condition.  So even if the pellets could be "the same shape" to get the answer you want, the .22 pellets are not being shot at an energy level that they would achieve from the same conditions in the shot cycle.

Bottom line, in pretty much any metric you want to use that deals with either efficiency, power or retained energy, the larger calibers are going to "win" - because by definition if the shape is the "same" but just scaled for caliber, the larger caliber pellets will be heavier, AND have a higher BC, AND will be shot more efficiently in terms of energy extracted from the air charge (to a point - an air charge that could effectively fire a .177 may not fire a .357 pellet).

Now, if you are talking metrics about putting a pellet on target at a longer range, that is completely different than fps, FPE, and all that.  They matter, but they are not the end game metric there . . .

[Wolverineshooter]

Yes, in anti-squirrel's tests, the velocities were close, although he didn't state if the barrels were the same length in both calibers.... A common .177 cal conversion on the 2240 (which has a 7.5" barrel) is to use the 10.1" barrel from a 1377.... My personal experience, using the same barrel length in different calibers, shows a much larger difference in FPE in favour of the larger caliber, when all other factors are kept the same....

The very title of this thread is problematic.... If a .177 and a .22 cal pellet are the same weight, they will NOT be the same shape....

Bob

Yeah, the difference is less than what I expected too. If barrel lengths are different that explains.

Well of course the shapes will not be eactly the same, just a way to say they are comparable except radius

[skorec]

Just notice
Larger caliber is able   stabilized the pellet more by larger shirt

[grand-galop]

Let's say the pellets weigh 15gr, with muzzle speed 700fps, 0.22 BC=0.016, 0.177 BC = 0.031 as in the case Bob calculated. Then the energy will be:

Yards   0.22 energy    0.177 energy
0          16.32              16.32
10        14.05              15.10
25        11.29              13.47
50        7.86                11.16
100       3.7                 7.7       

So 0.177 will have more killing power at a longer distance.


What it takes for the 0.22 to match the killing power of the 0.177? Let's increase the speed for the 0.22 to match the killing power of 0.177:

0.22 Muzzle speed    Muzzle power     Distance   Hitting power
700                          16.32                0              16.32
727                          17.60                10             15.10
768                          19.64                25             13.47
852                          24.17                50             11.16
1170                         45.59                100             7.7

So if your goal is short distance hunting, then 0.22 may do better if it has more power to begin with. But 0.177 will have advantage in the long distance that 0.22's higher initial energy may not be sufficient to compensate.

Did you see that it requires 46fpe for 0.22 to match the killing power at 100 yards of 0.177 with a muzzle power of 16.32? just because of less drag in 0.177.

The pellet makers should publish the BCs to help us with  the choice of pellets.

It open more question about efficiency...  And as far as twist rate, the discussion was discussed in another tread and someone mention the FX SMOOTH TWIST.. The efficiency in a heavier pellet could be increased at a certain pressure with the smooth twist due to less drag..

[rsterne]

The basic concept of using the same weight pellet in .177 and .22 cals is handicapping the .22 cal.... You must detune the .22 cal for that to take place, either by barrel length, pressure, porting, or some other means of artificially restricting the performance of the .22.... Then you are looking at the best possible case for the .177 cal, by choosing a very heavy pellet, with an excellent SD and potential BC.... With the question so heavily weighted in favour of the .177 cal, is it any surprise that you can "prove" that is it superior to the .22 cal ?....

Reality is what counts.... If this was reality, we would be pursuing smaller and smaller calibers to increase killing power, instead of the surge in popularity in Big Bore that is actually occurring....

Bob

[grand-galop]

The basic concept of using the same weight pellet in .177 and .22 cals is handicapping the .22 cal.... You must detune the .22 cal for that to take place, either by barrel length, pressure, porting, or some other means of artificially restricting the performance of the .22.... Then you are looking at the best possible case for the .177 cal, by choosing a very heavy pellet, with an excellent SD and potential BC.... With the question so heavily weighted in favour of the .177 cal, is it any surprise that you can "prove" that is it superior to the .22 cal ?....

Reality is what counts.... If this was reality, we would be pursuing smaller and smaller calibers to increase killing power, instead of the surge in popularity in Big Bore that is actually occurring....

Bob

I dont want you to be OFFENDED by what I am about to say..  The surge in big bore popularity is related to the opportunity to hunt bigger game that was intended for powder burners until recently.. I think the cost in the bigbore be slightly  less than 5 years ago is a big part of the surge too... I dont think it is negative to ask question about efficiency in the small bore domain because if you can have the same KILLING POWER in a .177 in longer range then a .22 , it is advantageous to hunt with the .177 in the capacity to use the air more efficiently..  LESS REFILL= MORE HUNTING..  I dont want to hunt rabbits with a 100FPE gun..