Pellet BC Improvements?

[ljgnemo]

I have been researching the performance of pellet guns vs actual firearms. Aside from the very obvious, orders of magnitude difference in chamber pressure and projectile weight, which is ok since we don't want them to be treated like firearms everywhere so easily, there is one major limiting factor to long range accuracy and energy retainment: ballistic coefficient of the pellet.

BC of a projectile is the characteristic of its ability to overcome resistance of the air as it travels through it. Since gravity acts on all objects the same way, light or heavy, BC is really the main factor which limit how far it goes, how much drop it has, and how much energy is delivered to targets. In general, the high the BC, the better.

Compare to firearm bullets, which exceeds 0.2 BC easily, and can go as high as 0.5-0.6 in some cases, pellets normally cannot exceed even 0.05. I have researched, and muzzle speed and projectile weight is not a necessary limiting factor to BC, some subsonic .223 as light as 40 gr could achieve nearly 0.2. So in general, give a particular calibre, weight, and muzzle speed, the BC is determined by the shape, balance and material of the projectile.

The pellets out there today are being marketed for a lot of vague descriptions of what they are good for, without a lot of technical data to back them up. And I can't seem to find any pellet maker market high BC. I am just wondering, why is this the case? Is it really that technically challenging and economically unfeasible to manufacture consistent, high BC pellets? I buy 150 pieces of JSB .30 44.75 grains for $15, which is on par or only slightly cheaper than most high performing .223 ammo, not to mention the casing and powder.

Aside from a appeal to all the pellet manufactures out there, maybe there could be some kind of crowd initiative to research and design a high BC pellet? I just can't wait for the day where you could actually make consistent and stable shots at 2-5 hundred yards, and take out a rabbit or two! 

 

[100mtrbench]

Because the skirt is a necessity with air rifles because of the low projectile speed. 

The skirt is almost kind of like a 'drag chute" , to keep the nose of the pellet pointing forward. 


However, there are some air rifles which are meant for shooting solids . But they are expensive, and loud, and suck lots of air. 

A .22 rimfire would be much more favorable and would win easily in the cost, sound, and accuracy department. 

The air rifle would still win in coolness though. There's something awesome about propelling big chunks of lead with nothging but air pressure isn't there ?  

Sorry for the language, it's dutch, and on top of that it's very "local" if you know what i mean LoL 

 

 

[30cal]

Traditionally one of the main advantages of shooting pellets is that they do slow down quickly and don't carry for a mile or two. They are safer than bullets. Of course those of us who like shooting longer ranges struggle with that limitation. The answer is to go for guns that can shoot slugs. The cost in air and ammo of course is very high. Most pellet guns are not suited for that with their choked barrels and not enough power.

 

[hasenpfeffer]

I know more about the history of the evolution of powder-burner bullets than I do about the history of airgun bullets. But however modern airguns came to be, I know that there's a close relationship between the twist rate of the barrels and the design of the pellets.

Long, heavy bullets designed for supersonic efficiency require high twist rates for stability. This is why powder burners have twist rates as high as 1:10 or even 1:8. Some projectiles are too long to be spin-stabilized, which is why APDS evolved into APDSFS, and the guns designed to fire it went back to being smoothbore cannons.

Air rifles commonly have twist rates as low as 1:20. This could be because older airguns didn't have the power to force a bullet through a tighter twist, or maybe just because a long twist was cheaper and easier to manufacture. And maybe skirted pellets evolved to allow easy expansion and gas-checking, or purposefully to limit their performance for safety. Whatever the reason, a 1:20 twist doesn't provide much stability, so the pellet has to basically be self-stabilizing. The only reason the twist is there at all is so a slightly irregular pellet will spiral instead of veering off in one direction.

I don't know if any PCPs have been designed with tighter twist rates. Such a beast might be able to accurately fire a less inherently stable pellet with a higher BC. There are some commercially available pellets that are almost like tiny Minie balls. But I doubt it could fire a solid boat-tail bullet like a spitzer, at least not without some kind of gas check. I'd be happy to be proven wrong on that!

 

[ajshoots]

I believe .22's tend to be around 1:18, .25's 1:16, and I know the .257's use 1:14. I have a 1:22 twist .25 barrel that shoots horrible and the same barrel but in 1:14 is said to be rather accurate.

 

[bill_dd97]

Try light or even alloy pellets in that 1:22 barrel.