Why FPE?

[Doug Wall]

"But I just get the impression that FPE is the be all and end all with many airgunners."

That's odd. I've been shooting airguns for almost 60 years, and I don't know any airgunners that fit that description.

[Bicycleman]

"But I just get the impression that FPE is the be all and end all with many airgunners."

That's odd. I've been shooting airguns for almost 60 years, and I don't know any airgunners that fit that description.

Well, Doug, I have been shooting air guns for about 70 years.  And I do fit the description in your first sentence above.  So maybe I am the first?

[Bill_in_TR]

Steve,

 Of course velocity doesn't equate to accuracy. But if I am sighted in at a particular range and wanted to be able to hit things at other ranges then the two most important things I need to know are velocity and BC.

Doug,

That comment I made was based on many threads on here over the last few years I have been visiting this site. If you haven't seen it in 60 years then I am sorry if you took offense. You must not read the same stuff I do.

Someone earlier said they like to see FPE,velocity and pellet type when people report performance. I completely agree.

[mobilehomer]

Simply put, known fpe is a better unit for comparison. Known fps is better for shooting.

[rsterne]

Known FPE is also critical for the choice of gun for a given task.... You might have two guns that shoot 950 fps, one with a 10 gr. pellet (20 FPE) and one with a 200 gr. slug (400 FPE)…. Only one would be a suitable choice for deer.... When I am looking for a pellet/slug for a given airgun, I automatically start looking at weights that are the FPE divided by about 2.... That is because I choose to tune my airguns wherever possible at about 950 fps, because that is the best compromise between trajectory and wind drift.... I look for a projectile that is accurate at about that velocity whenever possible.... If I can't find one, then I may look at heavier ones, particularly if the quarry is generally at 50 yards or less....

While BC can make a slight difference in trajectory, most of how flat a gun shoots is due to the velocity.... It takes a large difference in BC to see any significant difference in POI within the 50 yard range that most airgunning is done.... Even at 100 yards, you will find little difference in POI between slugs of different BC.... Pellets, of course are a different matter, a wadcutter will drop a lot more than a good round nose pellet.... Anybody here shoot wadcutters at 100 yards?.... I didn't think so.... 

BC is the critical factor, of course, in limiting excessive wind drift.... Velocity only has a very minor effect, and in fact between 800-950 fps the difference in drift at 50-100 yards is negligible.... If you use a MV of over 950 fps, the drift increases, and it will be about 50% more at 1500 fps, rather than less.... In fact, for a given slug, you would have to drive it at about 2500 fps to reduce the wind drift to what it is at only 900 fps.... 

Bob

[Thane]

When tuning an "air-gun-engine" FPE is the primary "budget" that can generate a range of secondary FPS depending on needed application.

This audience is wide some interested in take down force others distant paper punching, and some endless shot strings. FPE is a common metric all can use to their own end through pellet selection.

[anti-squirrel]

I always fall back on archery and trebuchets when somebody brags about FPS, no matter the projectile launching method.

A 100 pound stone hurled at 200 FPS going 300 yards is going to WRECK some stuff.  Talking some SERIOUS FPE.

Velocity/FPS means absolutely nothing without knowing projectile mass, first, foremost, and always.    Anybody ever hit a deer at 35 MPH?  Your car is a projectile moving LESS THAN 52 FPS.  Most Bambis will not walk away.  Again... FPS is worthless without knowing MASS.  FPS + MASS gives an approximation of FPE.

Since many airgunners own chornnographs, we usually qualify our FPS bragging by ALSO including the pellet type and weight.  In fact, almost every thread you look through regarding 'FPS' includes the pellet type, shape, and weight.  The FPS question is nullified without knowing the FPE, since that's what we're looking for- even target shooters.

Imagine a 200 yard field target shot and the pellet bounces of the silhouette.  Not much use since the FPE is too low.

[HunterWhite]

I always fall back on archery and trebuchets when somebody brags about FPS, no matter the projectile launching method.

A 100 pound stone hurled at 200 FPS going 300 yards is going to WRECK some stuff.  Talking some SERIOUS FPE.

Yeah serious,
Muzzle Energy = 62189.05 foot-pounds !

Oh. I know,  there you go with the FPE again.
🤐

[GLPalinkas]

Competition rules have different FPE requirements. World Field Target, for example, requires under 12 FPE. If someone tells me a gun I’m interested in is shooting 900fps first thing I want to know is “ with what weight pellet”. I shoot Open Class PCP Field Target and that allows up to 20 FPE.

Hope this helps understand our FPE obsession. Lol

Gary
Venice, FL

[Bayman]

Known FPE is also critical for the choice of gun for a given task.... You might have two guns that shoot 950 fps, one with a 10 gr. pellet (20 FPE) and one with a 200 gr. slug (400 FPE)…. Only one would be a suitable choice for deer.... When I am looking for a pellet/slug for a given airgun, I automatically start looking at weights that are the FPE divided by about 2.... That is because I choose to tune my airguns wherever possible at about 950 fps, because that is the best compromise between trajectory and wind drift.... I look for a projectile that is accurate at about that velocity whenever possible.... If I can't find one, then I may look at heavier ones, particularly if the quarry is generally at 50 yards or less....

While BC can make a slight difference in trajectory, most of how flat a gun shoots is due to the velocity.... It takes a large difference in BC to see any significant difference in POI within the 50 yard range that most airgunning is done.... Even at 100 yards, you will find little difference in POI between slugs of different BC.... Pellets, of course are a different matter, a wadcutter will drop a lot more than a good round nose pellet.... Anybody here shoot wadcutters at 100 yards?.... I didn't think so.... 

BC is the critical factor, of course, in limiting excessive wind drift.... Velocity only has a very minor effect, and in fact between 800-950 fps the difference in drift at 50-100 yards is negligible.... If you use a MV of over 950 fps, the drift increases, and it will be about 50% more at 1500 fps, rather than less.... In fact, for a given slug, you would have to drive it at about 2500 fps to reduce the wind drift to what it is at only 900 fps.... 

Bob

I learned a lot today from this post and some of the things I believed true, I proved wrong while verifying your claims to be correct. Thank you

[kerplunk]

Doug,

Absolutely the energy delivered is a factor that must be considered when hunting. But it is not the muzzle energy that matters. It is the energy DELIVERED that matters. To figure that out you need to know velocity, ballistic coefficient and weight of the bullet. No question the caliber influences the choice for hunting a particular animal.

But you also have to hit the animal. And if all you have is FPE what crosshair or dot on your reticle do you use. I want to be able to determine bullet/pellet drop so that I can figure out how to hit the game or other target. And to determine whether I can knock down or kill what I am shooting at I need to know the energy at the point of impact not what it is at the muzzle.

As others have stated, muzzle FPE is usually similar with different weight and BC pellets. So if you know FPE of a gun you can approximate FPS, even with pellets you haven't shot. You could get this info from the pellet + FPS info you would like to see, but it would require an extra step. Thus, FPE is more useful than FPS when approximating the trajectory of any pellet fired from that gun, as it allows you to more quickly approximate FPS. Of couse BC is the other variable here, but you would need to know that either way. So with FPE you can approximate the trajectory and energy at impact of any pellet with one less step than with FPS + pellet weight of a specific pellet.

[Nomadic Pirate]

FPE is a quick baseline so you have an Idea of the gun power level,.....then you can go into specifics with what velocity various pellets of different weights clock.

FPE is easier to understand at a glance for a general idea of where the gun is.

[fwbsport]

Velocity is always the baseline for me to judge power and ability to hit something at so many yards.  I have heard FPE so much in air rifles I've forgotten what it means to say a measly 12 foot pounds for this when that is about a 10th of a .32 auto.  Only pellet gun hunters use FPE and that is just one way of expressing the difficulty of using an air rifle over a .22 rimfire.

Get into velocity with any pellet and it has to be over 600 fps to make me look at what caliber, and then there are lots of .177s out there filling the mark with that, then go larger to .20 in 600 fps and see how that is and then try a .22 at 700 and a .25 at 650 to see how these "low" velocities are assigned to the pellet that always gets the job done.

Then someone has a a 1000 fps pellet--or is advertised as such with a tin or aluminum pellet! Yeah sure!  What does it get with real lead pellets?  Who tells the truth around here about velocity and ft lbs?

I've seen major discrepancy in posted velocity here and there not matching at all what real chronographs are saying about my rifles from AOA who use an Oehler with two screens. 

The FPE can always be converted back into velocity if anyone like me likes it that way.  But FPE? That's reserved for dangerous game guns shooting big bullets around twice the speed of sound!
 

[PCPhack]

Wow. I shoot airguns and firearms, and I can say that for me velocity means nothing without knowing the bullet weight also, as I mentally can estimate the kinetic energy then (fpe). To me, FPE is the most valuable thing to know to understand how much power a gun produces as it combines those two. For ballistics and all, yes speed and BC are needed, but that is a different topic.

[Nomadic Pirate]

Wow. I shoot airguns and firearms, and I can say that for me velocity means nothing without knowing the bullet weight also, as I mentally can estimate the kinetic energy then (fpe). To me, FPE is the most valuable thing to know to understand how much power a gun produces as it combines those two. For ballistics and all, yes speed and BC are needed, but that is a different topic.

Bingo !!!!

[Nomadic Pirate]

Velocity is always the baseline for me to judge power and ability to hit something at so many yards.  I have heard FPE so much in air rifles I've forgotten what it means to say a measly 12 foot pounds for this when that is about a 10th of a .32 auto.  Only pellet gun hunters use FPE and that is just one way of expressing the difficulty of using an air rifle over a .22 rimfire.

Get into velocity with any pellet and it has to be over 600 fps to make me look at what caliber, and then there are lots of .177s out there filling the mark with that, then go larger to .20 in 600 fps and see how that is and then try a .22 at 700 and a .25 at 650 to see how these "low" velocities are assigned to the pellet that always gets the job done.

Then someone has a a 1000 fps pellet--or is advertised as such with a tin or aluminum pellet! Yeah sure!  What does it get with real lead pellets?  Who tells the truth around here about velocity and ft lbs?

I've seen major discrepancy in posted velocity here and there not matching at all what real chronographs are saying about my rifles from AOA who use an Oehler with two screens. 

The FPE can always be converted back into velocity if anyone like me likes it that way.  But FPE? That's reserved for dangerous game guns shooting big bullets around twice the speed of sound!
 

Sorry,...this post makes no sense to me LOL

[fwbsport]

Velocity is always the baseline for me to judge power and ability to hit something at so many yards.  I have heard FPE so much in air rifles I've forgotten what it means to say a measly 12 foot pounds for this when that is about a 10th of a .32 auto.  Only pellet gun hunters use FPE and that is just one way of expressing the difficulty of using an air rifle over a .22 rimfire.

Get into velocity with any pellet and it has to be over 600 fps to make me look at what caliber, and then there are lots of .177s out there filling the mark with that, then go larger to .20 in 600 fps and see how that is and then try a .22 at 700 and a .25 at 650 to see how these "low" velocities are assigned to the pellet that always gets the job done.

Then someone has a a 1000 fps pellet--or is advertised as such with a tin or aluminum pellet! Yeah sure!  What does it get with real lead pellets?  Who tells the truth around here about velocity and ft lbs?

I've seen major discrepancy in posted velocity here and there not matching at all what real chronographs are saying about my rifles from AOA who use an Oehler with two screens. 

The FPE can always be converted back into velocity if anyone like me likes it that way.  But FPE? That's reserved for dangerous game guns shooting big bullets around twice the speed of sound!
 

Sorry,...this post makes no sense to me LOL

Back in 1988 I bought a Remington 700 BDL in .17 Remington.  That would kill faster than most .22s outside of the Swift and .22-250.  I also have the .204 Ruger, another hot one and accurate.  The .17 Rem did around 4000 fps at the muzzle and at 200 yards would kill as fast as the Swift and other.  The .204 is accurate and a bit heavier with the same speed without much difference in killing. 

They say it takes 2000 ft lbs to kill an elk.  We say it takes 4 ft lbs to kill a rabbit shot exactly right in the head.  What I was trying to show is the KE compared here shows how silly we are to use ft lbs instead of velocity, because anybody in ballistics would think we're shooting mustard seeds compared to the real ammunition found in centerfire rifles.

Yes the conversation makes more sense to air gunners ONLY to use 7 grains of lead........

[Nomadic Pirate]

Velocity is always the baseline for me to judge power and ability to hit something at so many yards.  I have heard FPE so much in air rifles I've forgotten what it means to say a measly 12 foot pounds for this when that is about a 10th of a .32 auto.  Only pellet gun hunters use FPE and that is just one way of expressing the difficulty of using an air rifle over a .22 rimfire.

Get into velocity with any pellet and it has to be over 600 fps to make me look at what caliber, and then there are lots of .177s out there filling the mark with that, then go larger to .20 in 600 fps and see how that is and then try a .22 at 700 and a .25 at 650 to see how these "low" velocities are assigned to the pellet that always gets the job done.

Then someone has a a 1000 fps pellet--or is advertised as such with a tin or aluminum pellet! Yeah sure!  What does it get with real lead pellets?  Who tells the truth around here about velocity and ft lbs?

I've seen major discrepancy in posted velocity here and there not matching at all what real chronographs are saying about my rifles from AOA who use an Oehler with two screens. 

The FPE can always be converted back into velocity if anyone like me likes it that way.  But FPE? That's reserved for dangerous game guns shooting big bullets around twice the speed of sound!
 

Sorry,...this post makes no sense to me LOL

Back in 1988 I bought a Remington 700 BDL in .17 Remington.  That would kill faster than most .22s outside of the Swift and .22-250.  I also have the .204 Ruger, another hot one and accurate.  The .17 Rem did around 4000 fps at the muzzle and at 200 yards would kill as fast as the Swift and other.  The .204 is accurate and a bit heavier with the same speed without much difference in killing. 

They say it takes 2000 ft lbs to kill an elk.  We say it takes 4 ft lbs to kill a rabbit shot exactly right in the head.  What I was trying to show is the KE compared here shows how silly we are to use ft lbs instead of velocity, because anybody in ballistics would think we're shooting mustard seeds compared to the real ammunition found in centerfire rifles.

Yes the conversation makes more sense to air gunners ONLY to use 7 grains of lead........

  .....

[PCPhack]

  What in the world.

Thst sounds like conflating many topics to end at some sort of organic hunters understanding.

Sorry, but I think more scientifically about the topic of power.

"Killing power" is an ambiguous term as there are many aspects and ways to kill.

[bear air]

LOL, heating up...