chrony testing speed shots [more results]

BTW, I said the BC for a CP is probably not known but I was intending to type that the BC for that pellet at transonic or supersonic speeds is probably not known…

Yeah, the lighter pellet going mach 2 will carry a lot of energy but getting it to that speed is a major challenge! You can’t do it just with more pressure or a bigger valve, you’re going to hit a wall at about 1600fps that way and the air consumption will be enormous too.

Now, if you can figure out a way to flash heat the air as it flows through the valve you can raise the LSOS and increase velocity. You might also go the path of NASA and use hydrogen as the gas and also heat the flow path and get those speeds. The problems are obvious! The heating device has to be powered and effective and using hydrogen just might carry some safety risks you’re not as equipped as NASA to deal with!

While it is possible to use a gas not actually on fire to propel a slug at high speed, the practical limitations and drawbacks just make more mass and reasonably easy to achieve speeds a far better option for delivering energy to the target.

Playing at the extremes is always fun as an experiment or just as a lark but generally gets old quick. For instance, if you could shoot a 30gr .22 slug from a condor at 3000fps but it took a fully charged diesel truck battery to power the magnetic and radiant heat elements and a double sized tank full of hydrogen that dumped on every shot, that would lose it’s luster fast. Likewise, shooting a 500gr slug the length of a pencil that tumbles out the barrel with a lot of energy would not hold your attention for long either!

We do spend a lot of time talking energy here but there is also momentum to consider and also energy retention. Pretty much the same thing in effect: In the world of practical airgun projectiles, the heavier slugs generally carry more momentum to the target and retain energy longer as they have highr BCs. Shooting at high subsonic speeds, the heavy projectiles don’t operate in the much less efficient trans/supersonic range but fly their whole trajectory with a higher BC. If you look at RJs numbers, you’ll see that while the heavier slugs started out slower, they arrived at the target as going as fast or faster than the lighter slugs. That’s a normal condition as they spent more of their flight in a more efficient profile.

Lot’s of the speed talk gets generated by accuracy talk… Supposedly, a flat trajectory is more accurate than a less flat one. The other idea is that the more time a slug is cruising to the target, the more wind drift it will exhibit. Both ideas seem logical and both are flat wrong. All ballistic trajectories have a curve and the only accuracy concern is repeating that curve. Wind drift is actually determined by the difference between how fast the slug would go in a vacuum compared to how fast it goes in air…that’s described by BC and the higher the BC (see heavy slower slugs) the less drift…even though the time to target is longer!

It’s amusing how everything we mess with regarding this hobby always comes back to speed but in the end, folks learn the same lessons (one way or another) and end up out shooting the new whipper snapper with the mega speed gun! Naturally, all the advertising about FPS adds to the lack of general knowledge and its up to us to inform the new hobbiests that they’ll be better off learning their holdovers than trying to shoot a pellet so fast it flys like a laser!

RJ

Either chairgun does not have the proper equations to deal with the hugely higher drag (and far more rapid deceleration) of pellets at SS speeds or there is a measurement problem.

I suspect that Chairgun can’t accurately handle those speeds. It is very difficult to calculate a ballistic path across the supersonic, transonic and subsonic ranges. The ballistic coefficient is very different for each of those regimes but you only entered one BC into Chairgun. I’ll bet the BC of a 14.3gr CP is not even known! Without solid BC info, you can’t calculate an accurate trajectory. For most uses Chairgun is very accurate given a good BC because the entire pellet path is subsonic.

Since Chairgun is calculating the trajectory with just the subsonic BC, it is greatly over-estimating velocity retained at the target. It might be an interesting experiment to see just how fast these pellets go from supersonic to subsonic. My guess; 11 yards for the CPs. You’d have to move the chrony a bunch and not shoot it and also calculate the local speed of sound but it could be done. Not much to gain other than some trivia though.

There is a slight chance that you have the chrony set up too close to the muzzle and you’re getting consistent but inaccurate measurements. This one’s easy to figure out. Just take a couple shots with the chrony at 6-8 feet from the muzzle and see what you get. The reading will be a little lower but unless they are hugely different, your current set up is OK.

This is with the Chrony at the target…? 😯

43fpe at impact… 😈

Must make one hell of a CRACK when you shoot! 😆

Just set your Chrony up by the target and not the muzzle. You have the accuracy so you won’t kill the machine! You can always put a 2×4 in front of the display… 😉

I’d be interested to see if you are passing through the barrier close to the target…