Why are .177 always less shot count than larger calibre?

[Missed_dinner]

I am usually quite a logical person but I can't work out why a .177 calibre rifle has a lower shot count than .22 or .25? It's got a smaller barrel and its firing a lighter pellet. So why would it use more air?

Does that thread title even make sense?

[p.j.]

.177 is less air efficient. More air is needed to get the pellet to full power in .177 than .22. Someone will explain in more technical terms, but would imagine the larger diameter pellet has more air acting on its skirt, at any given time.

[Artfull-Bodger]

It's a case of surface area, the larger the surface area the greater the force applied for a given pressure.

Pneumatics are inversely proportional, when compressing you get more pressure for a given force by reducing the area, and when using a force to move something you get more force for a given pressure by increasing the area.

So the smaller area means you have to push for longer to transfer the same amount of force, in other word you need to use a longer pulse of high pressure air to get the small diameter pellet up to the required speed.

Hmm no matter how many times I write this it never comes out as simple as it really is?

[Rich]

Try blowing down a straw, then blowing down a piece of hosepipe the same length. Which is easier?

[UrbanFox]

It's a case of surface area, the larger the surface area the greater the force applied for a given pressure.

Pneumatics are inversely proportional, when compressing you get more pressure for a given force by reducing the area, and when using a force to move something you get more force for a given pressure by increasing the area.

So the smaller area means you have to push for longer to transfer the same amount of force, in other word you need to use a longer pulse of high pressure air to get the small diameter pellet up to the required speed.

Hmm no matter how many times I write this it never comes out as simple as it really is?

This video by Rob Lane, although its explaining how a regulator works, will back up Artfull Bodger re surface area. I.e, the greater the area the less pressure required.
https://www.youtube.com/watch?v=Y8CN2PCGGQM

[bucketboy]

Like what the bodger says, just to highlight how ineffiecent .177 is, I replaced the 16" .177 barrel from one of my Rapids that was set at 11.7fte and swapped it for a 19" .25 ( everything except the probe remained the same) I was obviously expecting a power hike due to cal and length of barrel but was shocked when I checked it on the chrono, it was in excess of 21fte, nearly twice the power for the same air consumption. Another test without changing anything other than the barrel, I replaced the 16" .177 for a .177 barrel only 95mm long, it produced 7.5fte but was really loud.

Despite its ineffiecency, I still love the .177.

[Artfull-Bodger]

Very similar to my experiences, I have a Webley Vulcan with a gas ram that I turned up a set of barrels for , .177, .22 and .25, I have to set the rifle to just under 10ftlbs in .177 otherwise the .25 is illegal!

[Phil Russell]

As a rather daft analogy, imagine holding a ping pong ball and a squash ball. Then throw both of them as hard as you can. The heavier squash ball will travel much further.
Cheers, Phil

[woody2906]

Surely it is to do with the legal power limit of 12ftlbs energy. For the sake of argument say to achieve near the legal limmit a .22 pellet needs to be propelled at 600 ft/sec and as already stated the .22 pellet is the more efficient. Now to achieve the 12ftlb energy level with the .177 pellet it has to be propelled at nearly 800 ft/sec considerably faster than the .22. That is how I understand it

[Rich]

Precisely. And you have the same barrel length therefore less time in which to achieve this higher speed, coupled with greater frictional resistance.

[Rickenbacker]

Brian Cox said (on the telly), that there's a certain amount of energy in the universe, and it never changes.

If Brian carries a rock up to the top of a cliff, and drops it over the edge, it hits the ground with exactly the same energy as had been used for bringing it up there... less a small amount for say, air resistance. Which again, isn't 'lost' because it's friction or something, which heats the air by a tiny amount, which in turn heats the universe by a much smaller tiny amount.

But the point is, the total amount of energy in the universe never changes. It just gets transfered into different types of energy.

Isn't that amazing?

Therefore as we know that .22 is generally more efficent, the extra energy required for launching a .177 pellet (at equal ME) must (I guess) get transfered into more friction or something?

[Murphy]

Hold up a fishing umbrella in the wind.

Then hold up an umbrella you get in a cocktail.

[Bjacobs571]

as Rich said it takes more air to accelerate a pellet to a higher speed.
When the orginal Hatsan Galatian shot counts came out the .25 had the lowest shot count. In all 3 calibres they were pushing the pellets as fast as possible. The figures were for the full power rifles not the 12ftlbs versions

[Nemo]

Further to this, I am led to believe a .177 isn't more inefficient. It just uses more/a bigger squirt of compressed air to reach the higher speed required to get the full 12ft/lbs. if we only wanted to push all our pellets out at exactly the same speed, say 600fps, then a .177 would use less air/get a higher shot count than a .22? Hence I imagine, by using heavier .177 pellets means you get more shots from a fill. Surely if you've tuned your reg to give 11.5 ft/lbs with bis mags instead of 11.5 ft/lbs with 7.9gr Hobby's??? I think this is all correct?? Though in practice swapping between hobby/bis mags during a shooting session I don't think you'd notice an increase in shot count as it's probably negligible over the course of one 180 bar fill. You would have to "set" the gun to shoot bis mags at legal limit and shoot a few full air cylinders worth. Then adjust the gun to get legal limit Hobby's and shoot the same number of air cylinders worth and count the number of shots you got from full to empty. Has anyone ever bothered doing this and worked out the saving?
At least that's the way it's all been explained to me. Might be completely wrong.

Regards.

Nemo.