Why “shot count” is misleading.

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Centercut

Centercut

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It seems one of the recent key words and tricky phrases is “shot count”. As in, nice gun, good power, but what’s the shot count?

A totally rubbish question. The response should be:

At what FPE? Pellets or slugs? What caliber? What size tube or bottle? From what pressure down to what pressure?

I think what the Shot Count boys are really looking for is EFFICIENCY of the gun. What FPE/ cu-in of air used? That tells the story without having to ask all the specific questions.

If I’m told your gun shoots 75 shots at 78 FPE, but it’s with a 480cc bottle and shooting to 110 bar from 250 bar, yes it does get more shots than my gun shooting from 250 bar to 140 bar with a 240cc effective size tube and 33 shots. But my gun uses air more efficiently and has a higher FPE/ cu-in air used. So if we both go shooting for the day, I’ll refill my gun more, but if we take the same amount of shots I’ll use less air. Things that make you go hmmm...

1589310428_5502468835ebaf3dc72bfa9.30624441.jpeg

 
It seems one of the recent key words and tricky phrases is “shot count”. As in, nice gun, good power, but what’s the shot count?

A totally rubbish question. The response should be:

At what FPE? Pellets or slugs? What caliber? What size tube or bottle? From what pressure down to what pressure?

I think what the Shot Count boys are really looking for is EFFICIENCY of the gun. What FPE/ cu-in of air used? That tells the story without having to ask all the specific questions.

If I’m told your gun shoots 75 shots at 78 FPE, but it’s with a 480cc bottle and shooting to 110 bar from 250 bar, yes it does get more shots than my gun shooting from 250 bar to 140 bar with a 240cc effective size tube and 33 shots. But my gun uses air more efficiently and has a higher FPE/ cu-in air used. So if we both go shooting for the day, I’ll refill my gun more, but if we take the same amount of shots I’ll use less air. Things that make you go hmmm...
Click to expand...


1589038647_13948701015eb6ce37cab586.17251284.gif

 
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True...but efficiency also can change at different power levels so that isn't a perfect answer either. In fact, efficiency has a tendency to be inversely proportional to power...especially as you approach an airgun's maximum power capability.

I think it is OK to say the shot count along with the power level you achieve that shot count with. I've also seen people quote different shot counts at different power levels. I don't think it is necessary to quote the gun's air capacity as that information is readily available online.

For example, my .22 AEA HP Varmint gets about 50 shots at 39 fpe with 20.2 NSA slugs from 200 bar down to 125 bar. It will do as much as 45 fpe with heavy pellets that have less friction but I prefer the slugs which are as accurate as any pellet in the gun and have more power downrange and buck the wind better to boot.
 
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I totally agree! I always look at the cylinder size, then the fill pressure, then regulated pressure. Then take the 250bar -125bar = 125 bar of usable pressures. then mutability by the bottle size .5L= 75 something?? bars per Liter? I don't know...

I'm not sure what exactly 75 stands for. But, I use that number to compare other cylinders and bottles. 

Example: A gun with 250cc tube with a 250 to 150bar fill will get 100 x .25 = 25 something



Then a step further- take gun #1 50 divided by 25fpe per shot = 2, the same gun at 50fpe = 1. Higher this number more shots you can expect. I have this formula worked out in my head for my .22 guns. 

But it is not always correct because pellet and slugs have different friction so you have to use more of that number to propel slugs.
 
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Maybe yet a different take...

Shot count only becomes important to me AFTER I make a choice on what power and features I want in 'the next gun' (features include bottle/tube size so the answer is relative).

But then again, when I discuss shot count, its usable shots for the intended purpose.

I have a .177 Wildcat that shoots as well at 240bar as it does at 110 and everywhere in between and that's close to 100 shots at 19fpe. It's all stock FX. (got lucky with a good .177 FX barrel) . I bought a Huma reg for it but I ain't touching anything on the gun unless something fails.

I agree with original premise but also would rather fill after 100 shots than 50 given the same performance, regardless of efficiency...…
 
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Maybe yet a different take...

Shot count only becomes important to me AFTER I make a choice on what power and features I want in 'the next gun' (features include bottle/tube size so the answer is relative).

But then again, when I discuss shot count, its usable shots for the intended purpose.

I have a .177 Wildcat that shoots as well at 240bar as it does at 110 and everywhere in between and that's close to 100 shots at 19fpe. It's all stock FX. (got lucky with a good .177 FX barrel) . I bought a Huma reg for it but I ain't touching anything on the gun unless something fails.

I agree with original premise but also would rather fill after 100 shots than 50 given the same performance, regardless of efficiency...…
Click to expand...

Yeah its like having two cars that make the same power and get the same mileage. One has a bigger gas tank, which would you rather have on a road trip?
 
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It seems one of the recent key words and tricky phrases is “shot count”. As in, nice gun, good power, but what’s the shot count?

A totally rubbish question. The response should be:

At what FPE? Pellets or slugs? What caliber? What size tube or bottle? From what pressure down to what pressure?

I think what the Shot Count boys are really looking for is EFFICIENCY of the gun. What FPE/ cu-in of air used? That tells the story without having to ask all the specific questions.

If I’m told your gun shoots 75 shots at 78 FPE, but it’s with a 480cc bottle and shooting to 110 bar from 250 bar, yes it does get more shots than my gun shooting from 250 bar to 140 bar with a 240cc effective size tube and 33 shots. But my gun uses air more efficiently and has a higher FPE/ cu-in air used. So if we both go shooting for the day, I’ll refill my gun more, but if we take the same amount of shots I’ll use less air. Things that make you go hmmm...
Click to expand...

So is it way way better if it has a bigger tank and even more efficient at the same power level?
 
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Totally get where you are going, but sometimes shot count can be more important that efficiency. I like knowing I can go out for a quick shooting session out back before dinner and get 100 shots and not take the air tank as well. One less thing to carry. If I was taking the .30, I would have to take the tank out as well, or stop at at 30-40 shots.
 
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Rubbish to say rubbish from such a narrow perspective. Airgunners use their guns for different things, and often have different criteria for what’s good. With respect to “shot count”

I offer a few examples:



A. A 10M target shooter may want the ability to practice an entire “session” without refilling the gun, sometimes up to a hundred shots.

B. A Silhouette shooter may settle for maybe 30-50 shots, since its rare to fire more than 15 between relays

C. A rabbit or bird hunter may be satisfied with even a dozen shots.

D. A short range tin can -plinker might be happy with 40 shots, but might like more.

note: none of the above shooters need or even desire “magnum” level power by modern Standards ... meaning say, over 30fpe. Most count “good shots” as all pretty much to the same accuracy level.

Sure shot count at a given power level can be important, esp if recharging the gun is tedious or expensive, or impractical due to portability of charging equipment, but barring rules or restrictions for certain games, shot count isn’t tied closely to efficiency based on gun size.

Sure, tuning for better shot count at a certain power level can be fun, and is a popular topic, and I personally have spent countless hours tuning and discussing the topic, but its really not all that to many many airgunners.

Its like the “high velocity” allure many new airgunners have, but moved along to “high energy”, “high shot count”, “high efficiency”, and the holy grail, 
“sub-moa accuracy at long range” .... fun for some, esp for discussion, but not really all that to many typical airgun shooters.

I say, leave more room for different perspective when it comes to brands, calibers, airgun uses, etc.



So ... specs in adverts regarding shot count can help a prospective buyer decide if it fits his needs, just like overall weight, caliber, and price .... with little need to discuss efficiency, since that is sort of implied in the gun’s size, charge pressure and use category.
 
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I agree ... generally when I've made statements of such have also stated the power and efficiency numbers and how figured.

In a recent build done that for me at least is a HIGHER power tuning in .25 caliber with pellets, it went like this:



* Copy and past from original thread.

Shooting the Benjamin 28 grain dome pellet at @ 960/970 fps guns cruising along at an easy 58 ft-lbs. Last full tank string of shots taken started at 3000 psi and after @ 62 shots both gauges were at 2K and just showing movement lower. * So were seeing 62 shots on 1000 psi off a 500cc bottle.

The numbers using Lloyds calculator has it at: avg FPE/cuin per shot 1.72 with avg PSI used per shot 16

Damnnnn I'll take that too the bank any day, any where !!



YES lowering air use at any power is important for efficiency.



Scott S
 
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Shot count = available volume / volume released per shot.



FPE per CI = FPE / cubic inches of air released per shot



Either metrics significance depends on your personal opinion/needs. The guy shooting a .50 cal making 450+ fpe doesn't care much about shot count and their efficiency, the guy with twin 350 cc bottles certainly cares about shot count, the guy making sure hes tuned so his valve is closed when the pellets approximately 30% down the barrel cares about efficiency which increases shot count due to being tuned efficiently...



I wouldn't say shot count is misleading. FPE/Ci is just as misleading without enough information. Both metrics are only ideal when provided with the whole picture. 1.8 FPE/Ci at what energy level? 20 fpe? 40 fpe? making 2 FPE/Ci in a .30 cal at 30 fpe isn't hard, but doing it in a .177 cal is nearly impossible, which means the number by itself can be just as misleading.



FPE/Ci tells more about when the guns valve is closing, thats about it... 1~ fpe/ci nearing 50% barrel distance upon valve closure, and 2~ fpe/ci nearing 5% barrel distance upon valve closure (many variables alter the results, such as port size, plenum volume, pressure) so using this metric for comparison is the same as saying " yea I close my valve at 33% "...not sure how that compares..



To get a better picture you would need the following data IMO:

PEAK FPE output and its Fpe/CI...and the average pcp will be within .9 - 1.2 fpe/ci using these numbers. Calculating based on peak closes a large gap that is rather unnecessary if comparing one air gun to another when using fpe/ci. I like to use both this in conjunction with fpe per inch of barrel.



For example, a 20" barrel making 30 fpe from a .177 versus a 20" barrel making 60 from a .25 cal. The .177 ca is 1.5 fpe per inch of barrel, the .25 cal is 3. The .177 cal makes 50% less fpe per inch of barrel, now lets consider its surface area. .177 = .0246 sq inches, .25 cal = .04908, which means the .177 has 50% less surface area.


So 3 (fpe per inch barrel .25 cal) / 1.5 (per inch barrel .177 cal) = 2 (difference in fpe / inch per barrel) * .50 (difference in surface area) = 1 (equal fpe per inch barrel given the surface area)...this is by far the best way IMO to compare one rifle to the next, even when considering calibers. The only exclusions in this calculation are operating pressure, port size , plenum size , and valve flow efficiency...YMMV. I personally don't rely on any single metric for comparison.



-Matt
 
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Shot count = available volume / volume released per shot.



FPE per CI = FPE / cubic inches of air released per shot



Either metrics significance depends on your personal opinion/needs. The guy shooting a .50 cal making 450+ fpe doesn't care much about shot count and their efficiency, the guy with twin 350 cc bottles certainly cares about shot count, the guy making sure hes tuned so his valve is closed when the pellets approximately 30% down the barrel cares about efficiency which increases shot count due to being tuned efficiently...



I wouldn't say shot count is misleading. FPE/Ci is just as misleading without enough information. Both metrics are only ideal when provided with the whole picture. 1.8 FPE/Ci at what energy level? 20 fpe? 40 fpe? making 2 FPE/Ci in a .30 cal at 30 fpe isn't hard, but doing it in a .177 cal is nearly impossible, which means the number by itself can be just as misleading.



FPE/Ci tells more about when the guns valve is closing, thats about it... 1~ fpe/ci nearing 50% barrel distance upon valve closure, and 2~ fpe/ci nearing 5% barrel distance upon valve closure (many variables alter the results, such as port size, plenum volume, pressure) so using this metric for comparison is the same as saying " yea I close my valve at 33% "...not sure how that compares..



To get a better picture you would need the following data IMO:

PEAK FPE output and its Fpe/CI...and the average pcp will be within .9 - 1.2 fpe/ci using these numbers. Calculating based on peak closes a large gap that is rather unnecessary if comparing one air gun to another when using fpe/ci. A longer barrel will always win this war anyhow, be it using peak or tuned fpe/ci...so again, is this metric really fair? Or does peak fpe per inch of barrel signify more...



For example, a 20" barrel making 30 fpe from a .177 versus a 20" barrel making 60 from a .25 cal. The .177 ca is 1.5 fpe per inch of barrel, the .25 cal is 3. The .177 cal makes 50% less fpe per inch of barrel, now lets consider its surface area. .177 = .0246 sq inches, .25 cal = .04908, which means the .177 has 50% less surface area.


So 3 (fpe per inch barrel .25 cal) / 1.5 (per inch barrel .177 cal) = 2 (difference in fpe / inch per barrel) * .50 (difference in surface area) = 1 (equal fpe per inch barrel given the surface area)...this is by far the best way IMO to compare one rifle to the next, even when considering calibers. The only exclusions in this calculation are operating pressure, port size , plenum size , and valve flow efficiency...YMMV. I personally don't rely on any single metric for comparison.



-Matt
Click to expand...

Yeah good points here, should have added but was referencing a post a while back c'cut asking about efficiency and if someone would calculate for a 78fpe tune in .30 and thats what i got. The .22 number referenced was at 28fpe in .22
 
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