I've noticed from published chrony results that heavier pellets tend to shoot at higher energy than lighter pellets in the same PCP airgun. Can anyone explain the physics behind this?I realize that the kinetic energy (FPE) is (1/2)*m*v^2 and that this formula gets larger with larger mass (m). But using a heavier pellet will also cause the velocity (v) to decrease, which pulls the energy down. In a PCP airgun, why does mass seem to win out here?Why does the airgun put more energy into heavier pellets if the same charge of air is released in either case? Is air wasted in the case of a lighter pellet, i.e., is it out of the barrel before it is done accelerating? Can't think of any other explanation as of yet.
The heavier pellet travels slower, stays in the barrel longer, which allows the compressed shot of air more time to impart more energy to it before it leaves the barrel. So, the heavier pellet leave the barrel with a slower speed, but more energy than the lighter pellet. The lighter pellet also left the barrel a little too early, leaving behind wasted air. That is the simple answer.
PCPs & MSPs do tend to produce more energy with heavier ammo because it makes them more air efficient. I use the heaviest ammo I can, within reason, that's not too loopy, in my PCPs & MSPs for just that reason.
It's called momentum. Objects at rest, tend to stay at rest. Objects in motion tend to stay in motion. Science 101. Higher mass carries higher momentum. Too complicated? Try this. Rather get hit by a feather traveling at 30 mph, or a bus at 30 mph. Get it?Knife
Quote from: rjp on January 16, 2020, 05:06:04 PMI've noticed from published chrony results that heavier pellets tend to shoot at higher energy than lighter pellets in the same PCP airgun. Can anyone explain the physics behind this?I realize that the kinetic energy (FPE) is (1/2)*m*v^2 and that this formula gets larger with larger mass (m). But using a heavier pellet will also cause the velocity (v) to decrease, which pulls the energy down. In a PCP airgun, why does mass seem to win out here?Why does the airgun put more energy into heavier pellets if the same charge of air is released in either case? Is air wasted in the case of a lighter pellet, i.e., is it out of the barrel before it is done accelerating? Can't think of any other explanation as of yet.The heavier pellet travels slower, stays in the barrel longer, which allows the compressed shot of air more time to impart more energy to it before it leaves the barrel. So, the heavier pellet leave the barrel with a slower speed, but more energy than the lighter pellet. The lighter pellet also left the barrel a little too early, leaving behind wasted air. That is the simple answer.But there is a caveat to this - there is a curve. If you use a light pellet and get less energy, but as you increase the pellet weight and energy goes up for the same shot of air. But if you keep increasing the weight of the pellet, at some point, the energy level starts coming down. That is because the same "shot" of air cannot efficiently propel that too heavy pellet in that barrel anymore, and the overweight pellet peaks and even slows down before it leaves the barrel. In this case, you need either higher set pressure or a larger plenum in order to get more energy to this heavier pellet.
Quote from: frank320 on January 16, 2020, 05:55:57 PMQuote from: rjp on January 16, 2020, 05:06:04 PMI've noticed from published chrony results that heavier pellets tend to shoot at higher energy than lighter pellets in the same PCP airgun. Can anyone explain the physics behind this?I realize that the kinetic energy (FPE) is (1/2)*m*v^2 and that this formula gets larger with larger mass (m). But using a heavier pellet will also cause the velocity (v) to decrease, which pulls the energy down. In a PCP airgun, why does mass seem to win out here?Why does the airgun put more energy into heavier pellets if the same charge of air is released in either case? Is air wasted in the case of a lighter pellet, i.e., is it out of the barrel before it is done accelerating? Can't think of any other explanation as of yet.The heavier pellet travels slower, stays in the barrel longer, which allows the compressed shot of air more time to impart more energy to it before it leaves the barrel. So, the heavier pellet leave the barrel with a slower speed, but more energy than the lighter pellet. The lighter pellet also left the barrel a little too early, leaving behind wasted air. That is the simple answer.But there is a caveat to this - there is a curve. If you use a light pellet and get less energy, but as you increase the pellet weight and energy goes up for the same shot of air. But if you keep increasing the weight of the pellet, at some point, the energy level starts coming down. That is because the same "shot" of air cannot efficiently propel that too heavy pellet in that barrel anymore, and the overweight pellet peaks and even slows down before it leaves the barrel. In this case, you need either higher set pressure or a larger plenum in order to get more energy to this heavier pellet.And this right here is fabled wormhole of AG shooting. Heavier will not always equal more FPE, as there is a limited/set amount of air provided for each shot, be it regulated or not. The trick is finding the right pellet (weight-wise, considering accuracy has already been accounted for) for the amount of air being used. OOOORRRRR....Using the right amount of air (hammer spring tension, regulator settings, valve work, transfer port work, fill pressures, etc) to give the pellet choice your desired FPE level. And then there's the combination of both; using a XX weight pellet to get into the ballpark figure of FPE you'd like to be at and then tuning the rifle's air consumption/output to most efficiently use air for that particular pellet. FPE levels too low? That means your pellet is oversized (bore size) or is too heavy for the amount of air being used. OR...it's too light and is traveling too fast. Using a break barrel as a simplified example, the shot of air utilized will have an optimal pellet weight for FPE levels. A Gamo Magnum can propel a 14.3gr pellet at 966FPS for 29FPE. The same rifle also propels an 18gr pellet at 845FPS, for 28FPE. Heavier does always equal more FPE, as there are limitations for the shot of air. A longer barrel helps with FPE numbers, but I think there's limitations to that too. I don't think you can take a 12FPE rifle and turn it into a 40FPE one by adding a 6ft barrel. Unless I'm wrong. All that being said? This is all just the tip of the iceberg. Rifling, slugs, pellets, BC, plenum sizes, barrel harmonics, cylinder sizes etc are ALL waiting for you to experiment with them. This is the Darkside, alright.
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