pressure 22air vs 22LR
Hi, can anyone tell me how is it possible that a .22 airgun (modified condor for example) can shoot almost at same velocity (1100 fps and more) as 22LR when using same 40grain bullets. The pressure which airgun operates is 2000-2900 psi vs pressue in 22lr chamber is arund 22000 psi. My guess would be that when bullet travels down the barrel airgun gives that 2000psi all the way to the end vs 22lr gives this 22000 psi only at the beginning, am i on the right track?
All Replies
Finally RiffRaff and DKowen attemped to answer the question. The other post and answers here had nothing what soever to do with the original posters question. Even Voltar answer has nothing to do with the question.
Yes Dwell time has a lot do with it. To understand it completely you world have to study internal ballistics. When smokeless power ignites in a contained space, (Case and chamber, it has a very fast burn time. Only a split millisecond. This is where the High spike in pressure comes from It is measured in CUP or copper units of pressure. And this pressure begins dropping just as fast. This Why we try to select a barrel length that best matches the pressure wave of the rounds we’re using. Ever notice most Magnums have 26″ bbl’s?
In the air gun (PCP) it is a steady push at near the full pressure from the get go.
And yes you can push a pcp past the sound barrier. I don’t know where one of the previous posters read that it can’t be done, as I and many others have done it . It’s nothing new. It’s just that the shape of a typical pellet becomes unstable when appraoching the speed of sound. And again when dropping back through the sof again. It make for any type of accuracy. This is why I and many others are playing with bullet shaped projectiles. In fact may next project is to use a .22 lr bbl. moded to fit my pcp, along with regular .22 long rifle bullets.
Please forgive the last paragraph, as it isn’t what you ask about, however several poster went in this direction for what ever reason. So I thought I would address it whils here.
Not wanting to upset anyone.
Mike
.22 PCP with 40 grain bullets at 1100fps??
.22 lr at ‘only’ 1100fps????
my point is that the basic facts must be true before a comparison of the why and how becomes logical.
Until then the comparison is apples and oranges.
PCP airguns do not get full pressure behind the pellet/bullet ever in the cycle as the pressure is dropping across the many restrictions before the pellet.
oh wel still fun.
Walter…
Thanx alot Mike, this was exactly what i ment and what you said is really the only logical explanation.
No offence, but the idea of the question really was’nt about shotcount, 30gr pellets, accuracy or potential power of 22lr compared to 22air
🙂 Anyway, meanwhile, when trying to find the reason myself, i have been playing with some internal ballitics calculators to get a pressure graph showing pressure behind 22LR bullet when it travels down the barrel.
Did’nt find anything for the 22LR, only for centerfires, but what i read out from centerfire graphs was that the pressure drops 5 times compared to what it started with. I belive for the 22LR the drop is much bigger, this is because when comparing 22LR to 22WMR, which is same rimfire cartridge only longer, you can see that the max chamberpressure is the same while velocities(standard) are 1200fps vs 2000fps. This can only be possible if 22WMR uses slower burning powder and as it has got more of it, will give more constant pressure and therefore higher velocity. This is what shows that 22LR is underpowered round for a powderburner and must loose pressure more rappidly than centerfires for which it is aprox. 5 times.
Anyway, this is how i would explain how .22air can achive what standard velocity 22lr can with pressure differences 10 times.
It might not be 100% of the whole truth, but definitly is the major factor.
Regards,
Alari
To add to what Knifemaker said, pressures die off rapidly in a powder burner, and at some point peak velocity gives way to friction, and the bullet actually slows if the barrel is too long. Anybody ever see a Remington XP-100 in .221 Fireball? (I’m working from memory here, so I hope I’m not too far off base with my facts.) In early models, it was found that the 10.75″ barrel was just long enough to stabilize the bullet, but still let it out at max velocity. Any longer, and the projectile slowed due to friction. Later models sported a 14.5″ barrel. My guess is that was for longer bullets and higher pressures available with hotter loads. Still, it was a “hand-gun” and had a shorter barrel than any rifle Remington made. And the velocities the handgun achieved are higher than those a rifle will achieve with the same round.
I use it as an example, compared against a Condor with a 24″ barrel. We know empirically that a 24″ puts out more velocity than an 18″, giving evidence to the fact that our pellets (slugs?) are accelerating for a greater proportional length of the barrel than is a powderburner. Perhaps it’s back pressure holding the valves open longer. Whatever the case, longer PCP barrels are superior to ever-longer powder-burners for raw velocity, accuracy not withstanding. (yes, i know faster ain’t always better)
So, what’s the optimum barrel length for a .22lr? Conventional wisdom says its 16″. Longer= friction related velocity loss. So why does Ruger offer them with an 18.5″ or 20″, or say, Kimber, with it’s 24″? They want to SLOW the bullet to subsonic for enhanced accuracy, without resorting to expensiv match ammo. They don’t have the luxury of using a heavier slug or turning in the tophat to slow things down. They either rely on subsonic ammo or friction. Where a rimfire will always have higher potential velocity/power than a .22 PCP, (1600fps in hypervelocity rounds?) when you slow one down sub-sonic to achieve it’s match-grade accuracy potential, it’s not too much more powerful than a hot-rodded Condor/Talon with similar pellet weight.
Sorry for the tangent.
I can under stand people miss understanding the spoken word, but what is going on here? I know we can all read.
Finally RiffRaff and DKowen attemped to answer the question. The other post and answers here had nothing what soever to do with the original posters question. Even Voltar answer has nothing to do with the question.
Yes Dwell time has a lot do with it. To understand it completely you world have to study internal ballistics. When smokeless power ignites in a contained space, (Case and chamber, it has a very fast burn time. Only a split millisecond. This is where the High spike in pressure comes from It is measured in CUP or copper units of pressure. And this pressure begins dropping just as fast. This Why we try to select a barrel length that best matches the pressure wave of the rounds we’re using. Ever notice most Magnums have 26″ bbl’s?
In the air gun (PCP) it is a steady push at near the full pressure from the get go.
And yes you can push a pcp past the sound barrier. I don’t know where one of the previous posters read that it can’t be done, as I and many others have done it . It’s nothing new. It’s just that the shape of a typical pellet becomes unstable when appraoching the speed of sound. And again when dropping back through the sof again. It make for any type of accuracy. This is why I and many others are playing with bullet shaped projectiles. In fact may next project is to use a .22 lr bbl. moded to fit my pcp, along with regular .22 long rifle bullets.
Please forgive the last paragraph, as it isn’t what you ask about, however several poster went in this direction for what ever reason. So I thought I would address it whils here.
Not wanting to upset anyone.
Mike
I don’t know. When you get some of those custom valves you can probably get power like that. Granted, it will be for 1 or 2 shots, but I think it’s possible. It’s one of those things where you wouldn’t get any shots, you’d have to get large slugs, which probably wouldn’t be accurate, and you’d have to do a lot of work on a valve.
I think it is possible, but it’s just not worth the effort. Could be wrong, but I’ve seen some of the stuff that you guys have made. I wouldn’t doubt much of anything with this stuff.
The basic premise is not correct. An airgun getting 1100fps will be doing that with a 21 grain soft lead Kodiak where a 22lr is doing 1200 to 1300 with a 40 grain hard lead bullet.
Airguns do well with what they are but they cannot compare to a 22 rimmy for power. It takes a very good performing .25cal airgun to get 22lr power. The trajectory now is another matter but we have fun anyways.
Walter….
In firearms ‘expansion ratio’ is working against you. Yes, there is a bunch of pressure *inside the case* as a peak, but as the bullet moves it drops fast. Consider that when it’s say half an inch up the bore, the volume is already doubled, all things being equal the pressure would be half. In practice, some powder is still buring so the pressure drops more slowly than you might think but the gas is also cooling rapidly so the pressure is lower for that reason. By the time it leaves the volume is probably 50 or more times greater.
This is why firearm barrels can be skinny at the end, but have to be thick near the breech.
Even in high pressure rounds like .223 or .308 breech pressures in the 50,000 range are down to a few thousand at ‘port pressure’ just before the round leaves and the expansion ratio is only a few times (bores have small volumes, cases are fairly large).
Springers have a similar thing, the peak pressure is very high, then the pellet moves a bit and it drops fast.
In general pellets get more pushed up the bore, bullets jammed up. A pellet body would never take that kind of abust I’d think.
Doug Owen
I get the question. I really have no idea, but here’s two guesses.
One, maybe it’s more efficient. Maybe all it needs is 3000psi of pressure, and .22lr pressure is using that 3000 down the barrel, and wasting the rest after it leaves the barrel.
Two, maybe it’s a time thing. Maybe that .22lr pressure dies out really really fast, but the 3000psi of the airgun stays with it all the way out of the barrel.
Again, don’t know for sure. Those just sounded good.
I was thinking the same thing riff, but am too polite to bring it up.
I don’t think anybody answered the question at all.
I too wondered the same thing. Why does it take 22,000 psi using gunpowder and only 3000psi using air to launch a 40 gr bullet @ 1100fps?
If that wasn’t the question, I must have misread it.
What could happen if the rest of the gun couldn’t handle it? I imagine the real weak point is the breech area. I can’t see the barrel exploding or anything. Maybe the breech explodes. I can see how that would suck. 😛
1100 fps i would say yes…its possible…get a 26+” barrel and custom high flow valve….
airguns and supersonic….no go
you can get power in an airgun that exceeds a .22lr….but you have to trade up in caliper, say a .308, 9mm .45 .50 these will make about 200 fpe, where the rimfire will only make 160 fpe !
they all stay around 700-900 fps, but has a bullet weighing 100+ grains
i did build one condor…well…i did a valve…which made the rifle launch EJ pellets at 30 grains supersonic for a bunch of shots….useable…no…accuracy was crap…but guy i made it for didnt care at all…just wanted power…even though i advised against it.
my .45 talon build made 604 fpe…allmost 4 times the power of 22lr
what im thinking is why you would want a airgun capeable of .22lr power
gamo and their 1600 fps is a marketing crap….they probably had the rifle diesel(the buning of oil in the piston chamber) as it shot the 5 grain pba ammo(also crap)
that light projecttile will loose a shitload of power/speed within a very short distance to airfriction, and since its so ligth penetration will be crap as well
i would rather shoot a wiehrauch what ever shooting a claimed 700 fps, than a gamo piece of shit claiming 1200-1600 (gamo uses light ammo to get better speeds, HW uses real lead and will be closer to real life results)
not to mention the gamo’s trigger is harsh, and so is the firing cycle, compare to the well behaved germans…
damn im off topic…but you get my hint i hope
ohhh fill your condor with helium….and it will make power like you wouldnt believe…..DONT USE ANY OTHER GASSES….helium is safe as it wont explode and burn…but if the rest of the rifle cant handle the extra flow you will be in for a nasty surprice…be warned
No is the simple answer , someone far more intelegent than me will explain in more detail but in the end its all about velocity and a live round will by far exceed any airgun at on or around supersonic speeds , delivering a bigger punch all the way as a result.
Bottom line, you cant make the bullet go faster than the speed of sound in the gas pushing it, but you can change the speed of sound in that gas!
Read Dave Spookys answers here : 1600 f.p.s. pellet rifle
http://www.practicalmachinist.com/vb/showthread.php?t=127421&highlight=airgun
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Your very welcome 134. And Exactly correct Chad.
Voltar, NASA has for years has been firing different grain weight into many different materials there at the Marshal Space Flight Center to get experience of what high speed particles can do to our equipment in space. A 1 grain nylon ball fired into pure lead will leave a 1/2″ to 3/4 inch crater that is over 5 ” wide when fired in excess of 50,000 fps. They are using extreme pressures. But is is in all reality a “Mega PCP”. So yes it can be done.
As to the gas to gas theory, that is external ballistics. Where the high speed gas meets stationary atmosphere comprised of the same gas or gasses.
In internal ballistics, the gases are sequestered from the atmosphere. The breach at one end, and the projectile at the other. The rapid expansion of the gasses in a powder burner, or the high velocity introduction of gases in a pcp do not in and of them selves propel the projectile. It is the pressure wave, or the shock wave that actually pushes the projectile down the bbl. The projectile is launched out the bore before these gasses ever contact the outside atmosphere. Since the projectile is a solid, rather than a gas, it is much less effected by the presents of the gasses. It is effected however by friction of the atmosphere. This is why we look for a high BC in our projectiles. It lessens or slows down this effect.
This is also how we propel a Jet Fighter through the sound barrier. Same principle. However, in the Jet, the projectile, (The Aircraft) is carrying the expanding gas, which is thrusting against the atmosphere, rather than the thrust being applied directly to the rear of the craft. The old opposite but equal reaction bit.
Hope this makes since. Just got back from a Knife show, and have been up for well over 24 hours. May be I should have stayed at a Holiday Inn Express! (an inside American Joke!)
Perhaps I should have just stated, internal ballistics+ before contact with atmosphere, External+ from contact with atmosphere until at rest. Then we get into out side of earths atmosphere. A whole other set of rules!
Mike