Is it just because the lower caliber versions have lighter pellets or they are modified for lower power? Could you for example mod a .30cal pcp to shoot with the fpe of the .357cal version of the same rifle?
Why do the same pcp's at different calibers have so much difference in fpe?
- Thread starter Kavliaris
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1st off ... AREA of the greater bore diameter has more surface area for equal pressure to bear against.
Add more weight from a larger bore ( caliber ) net result will be more extracted power.
Can a .30 be made to have the power of a .357 ? At equal pressure NO
To get / have the smaller bore extracting more energy will require More pressure and then will require More Speed of projectile requiring More pressure again. Once speed gets @ 80% of supersonic ( AKA: Trans Sonic ) accuracy will likely start to deteriorate and efforts to push faster with a weight of projectile caliber can shoot will be in vain. If accuracy goes away in the search for power your pissing into the wind.
Sorta something like that ... lol
Add more weight from a larger bore ( caliber ) net result will be more extracted power.
Can a .30 be made to have the power of a .357 ? At equal pressure NO
To get / have the smaller bore extracting more energy will require More pressure and then will require More Speed of projectile requiring More pressure again. Once speed gets @ 80% of supersonic ( AKA: Trans Sonic ) accuracy will likely start to deteriorate and efforts to push faster with a weight of projectile caliber can shoot will be in vain. If accuracy goes away in the search for power your pissing into the wind.
Sorta something like that ... lol
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Force = Pressure x area
for .22 cal with radius of 0.11 inch @1000 psi
1000(psi) x 0.038 square in = 38lb
Vs .30 cal with radius of 0.15 inch @1000 psi
1000(psi) x 0.07 square in = 70lb
All things equal the greater surface areas equates to more force applied to the projectile. Now that's just the force exerted on the object the pressure is pushing or the projectile in this context. The FPE or the kinetic energy of the projectile is the simple calculation of weight and final speed at the muzzle, which is the direct results of the acceleration caused by the force exerted on the projectiles mass, duration of the force and friction of the barrel.
for .22 cal with radius of 0.11 inch @1000 psi
1000(psi) x 0.038 square in = 38lb
Vs .30 cal with radius of 0.15 inch @1000 psi
1000(psi) x 0.07 square in = 70lb
All things equal the greater surface areas equates to more force applied to the projectile. Now that's just the force exerted on the object the pressure is pushing or the projectile in this context. The FPE or the kinetic energy of the projectile is the simple calculation of weight and final speed at the muzzle, which is the direct results of the acceleration caused by the force exerted on the projectiles mass, duration of the force and friction of the barrel.
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Scott, I thought the effects of turbulence of trans sonic flight referred to projectiles that start at super sonic speeds, and slow to sub sonic during flight, before reaching the target. As you increase velocity, but remain at sub sonic levels, 80% of super sonic will be around 900 fps. That range has usually worked well in most of my rifles. Doesn't the "trans" refer to the transition from super to sub sonic? Or, in the case of a self-propelled projectile (an aircraft), just the opposite, building from sub to super sonic? But, I skipped physics, so I may be totally incorrect.
Ed
Ed
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i would think that if you start in the trans-sonic region you will already be introducing the turbulence.
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I thought the turbulence was the result of passing through the sound barrier, not approaching it. For example, if you shoot a HV rimfire at, say 1300 fps, at at 50 yard target, the bullet will slow to a sub sonic speed on the way. But the turbulence is in the air waves right behind it, and continues at that greater speed long enough to overtake the slowing bullet and cause disruption. Which is why all match rimfire ammo is in the 1050 velocity range. It certainly slows to this trans sonic speed on the way, but it is known for its stability. I have always read that this disturbance in the air results from passing through the sonic barrier. But again, volumes could be written about what I don't know!
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It can be both: 1) due to larger/smaller projectiles and 2) internal changes (adjustments or parts) in the gun to accommodate different power ranges, either to suit the projectile, or the sales market. Some markets have power limits and the guns must be throttled with different parts inside.
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It’s mass (weight of projectile) x acceleration (velocity) in a crude sense. A heavier pellet at the same speed has more energy than a lighter one.
The trouble is that once you get near, through and just over the sound barrier, the turbulence destabilizes the pellets. So typically the goal is to find the spot just enough under the sound barrier for stability for the best accuracy. Domed pellets tend to be 850-900 fps range with slugs being slipperier, given enough barrel twist to stabilize them, can go a bit higher.
Something like 5.56 center fire as an example is going 2000-3000fps range, well past speed of sound but also heavily stabilized by twist and speed combined.
Plugging numbers into a pellet FPE calculator will show you the changes as you change weights.
There are big bore air rifles that get well past the sound barrier now but you are dealing with hearing protection required levels of loud and even recoil to deal with. It’s kind of a different ball game.
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Fpe is a formula that take into considetarion weigh and speed of projectile.
I proposed a new formula in order to take into consideration the diameter of projectile in order to take also into consideration the damage in tissue for hunting purposes. I call it Hunting Energy Units (HEU):
www.airgunnation.com
I proposed a new formula in order to take into consideration the diameter of projectile in order to take also into consideration the damage in tissue for hunting purposes. I call it Hunting Energy Units (HEU):
Final formula for obtaining the Hunting Energy Units on Air Rifles.
Taking into consideration: a) That in Air Rifles (as it is when hunting with a bow and arrow) the killing power is related with size of damage (cut-hole) caused in vital tissues; b) That the damaged caused is related by a combinations of velocity (fps), weight (grains), diameter, density...
www.airgunnation.com Last edited:
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My P35-25 has almost exactly the same fpe as my P35-22. The 22 actually shoots a slightly heavier pellet. I shoot a H&N FTT in the 25 (20 grains) and a H&N Barracuda Match (21 grain) in the 22. I didn't force this outcome, I pick pellets by what is accurate and then try to push them 800-900 fps. Both these P35s are in this range. The reg pressure is higher on the 22, however, and the shot count is lower. It is easier to make more fpe on a bigger caliber.
My P35-177 cannot get to the fpe as it's big brothers. It shoots the heaviest "normal" 177 pellet, a 10.65 grain, at about 900 fps, faster than the other two. I don't want to shoot pellets any faster. I could try to find a really heavy 177 pellet but I have no desire to, it shoots well with the 10.65 and has enough energy for squirrels.
My P35-177 cannot get to the fpe as it's big brothers. It shoots the heaviest "normal" 177 pellet, a 10.65 grain, at about 900 fps, faster than the other two. I don't want to shoot pellets any faster. I could try to find a really heavy 177 pellet but I have no desire to, it shoots well with the 10.65 and has enough energy for squirrels.
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