Tuning .177 vs .22 shotcount

If the 177 and 22 are at the same fpe, and store the same amount of air at the same pressure, the 22 will have a higher shot count. The air has a larger area to push against with a 22 so it takes less air to get to the same fpe. 22 shot count tends to be less, as in your example, because the fpe is greater.

I used to have a practical example. I had a 22 and 25 caliber P35 both tuned to 32 fpe. Shot count was noticably greater for the 25. I've since retuned the 25.

There's the nuance of the efficiency of the air charge on a piston of a larger size ( pellet being the piston).


In practice between my 2 discos projectile weights are different, velocity is different, energy is equal and shot counts were equal.

I've leaned towards viewing air guns as fpe. My impact used to just shoot 50 fpe no matter the projectile weight. Velocity would just vary with projectile weight, no tune change

I've used both .25 and .22 calibers Taipan Veterans. The larger caliber is definitely more efficient with air usage. Tuned to the same FPE, the .25 caliber was getting 50% more shots on the regulator compared to the .22 caliber. On the other hand, tuned to the same reg pressure, the .25 was getting about 17 FPE more than the .22 and both guns were getting the exact same shot count at those tunes.

I don't have experiences with other guns of multiple calibers but I've seen specs and user tests where the difference between a small and larger calibers don't come close to what I saw with my Veterans. I come to the belief that, yes, a bigger caliber will generally be more air efficient than smaller caliber but to what extent also largely depends on the design of the gun such as the porting, valves, etc..

Also, from my experiences with my own guns, the higher the tunes, and the closer it get to the gun's theoretical maximum, the MORE air it uses. Going back to my Taipan Veteran Standard in .25 caliber, at 44 FPE it's getting 60 shots on the reg. However, maxed at at 55 FPE, it's only getting around 28 shots on the reg.

My Veteran Long at 40 FPE was getting about 40 shots on the reg. Tuned down to 30 FPE and it's more than double at 90 shots.

And to address your last question, no, you can't change a gun's FPE by simply changing the projectile weights. You have to actually change the gun's tuning.

I would worry more about accuracy than shot count. Those greens don't like to fly that fast.

Mm89 said:

Thanks for your answers.
I may have been a bit imprecise there.
Of course, I'm aware that the rifle needs to be readjusted to the lighter pellets.
I was just curious whether, with a good setup, you could achieve a similarly high shot count.
As you explained with your Vereran Long example, this is quite possible. Thanks for that.

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I can only speak to 177, 22, 25 and I can say that 177 was the most finicky to tune of the 3. At the same time my wishes are for groups and similar trajectories between guns because I will forget my dopes with so many toys and the standards ive put on myself for hunting shots.

In my guns, it is not precisely true that using a heavier projectile, with no other changes, produces the same fpe. If you said "within 1 fpe" I would agree, however. I shot a lot yesterday using my P35-22 using mostly 18 grain projectiles but also 21 grain. The 21 grain fpe was a little more than half a foot pound greater. From a practical standpoint I would agree they are the same. But not exactly. With a wider difference in weight I would expect to see a little more difference but still not much.

JimD said:

In my guns, it is not precisely true that using a heavier projectile, with no other changes, produces the same fpe. If you said "within 1 fpe" I would agree, however. I shot a lot yesterday using my P35-22 using mostly 18 grain projectiles but also 21 grain. The 21 grain fpe was a little more than half a foot pound greater. From a practical standpoint I would agree they are the same. But not exactly. With a wider difference in weight I would expect to see a little more difference but still not much.

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Only my impact does that, probably due to having the barrel length to use the air dose and a valve adjuster to help tame valve dwell. . The 22 disco I'm working on had the same tune this morning and shot 20 fpe with a 15.89 and 30 fpe with a 25 grain. Granted there 2ae a large velocity penalty and the heavies didn't group well.

Let's just say I look at my guns that are properly tuned for efficiency as fpe devices(within reason). So long as the propellant charge and duration is timed correctly you can have some fun with correlating numbers.

Almost any projectile-launching implement is more efficient in larger calibers and/or with heavier projectiles. That includes airguns, firearms, bows, and slingshots... at least. "More efficient" can mean produces more kinetic energy, or given the same kinetic energy in PCPS, more shots per charge.

It's a Physics thing.

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Mm89 said:

Hello everybody.

I have a question regarding .22 vs. .177
when it comes to air consumption.
Suppose I have two identical PCP rifles. One in .22 and the other in .177. Both shoot pellets of roughly the same weight (for example, light 10-grain pellets).
Would I expect the same results in terms of shot count and traction?

For example, I saw a video from "airgunsofarizona" where 190 shots at 18 ft/lbs were achieved with the Vulcan 2 in .177 (JSB 10.3 grain).
With the same weapon in .22 (JSB 18 grain), only 58 shots at 31 ft/lbs were achieved.

In this case, would the Vulcan 2 in .22 with lighter pellets (for example, if I use a "Field Target Trophy Green .22 with 9.57 grains) achieve a similarly high shot count as with the .177?

regards max

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Hi,
That's an interesting topic.

I was curious about it too, so I actually tested the difference in air efficiency based on caliber.
The combination of .177 and .22 bullets you mentioned is difficult in reality, so let's discuss .22 and .25 instead.

First, prepare two guns of the same model with different calibers. Both use 30gr slugs, and the regulator and spring are properly adjusted to achieve a muzzle velocity of 950 fps.

As a result, the .25 had lower regulator pressure than the .22. I speculate that the main cause of this is the difference in contact area inside the barrel, which affects movement efficiency.

However, when firing from the same fill pressure to each regulator pressure, I noticed that the .22 had a higher Shots per fill.
This is likely because the .22 has a smaller barrel capacity, resulting in better air efficiency.

However, this is not absolute, as there are many variables such as slug type and length (contact area), and the outer diameter that fits inside the barrel.

For example, if an extremely heavy (long) slug is used relative to the caliber, the SPF may decrease compared to using the same weight slug in a larger caliber. (For example, using a 20grain slug in a .177 caliber.)

Please share your test results as well.

it requires more speed to get it upto the same muzzle energy as a 22 pellet.

The .177 will be in the barrel for less time, so it requires more pressure behind the pellet.

If you have a .177 barrel about 30 % longer than a .22 barrel, you will get the same number of shots.

Think of it this way - you can either gently push a pellet over a longer distance using less force, or you can smack it really hard over a shorter distance using a larger force.

Another important factor is the .177 pellets are smaller than the .22 pellets.

The force which accelerates the pellet, is the pressure times the area behind the pellet.

The .177 pellets have an area about 30% less than the .22 pellets.