Can velocity increase with shorter barrel in a firearm?
I watched an episode of American guns where they shorten a Thomson, I think from 18 to 16,1 inch and when they crony it the velocity of the 16, 1 inch was greater by 40 fps. Is this possible?
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i cant tell you that, as i havent tried the experiment in .22, but in .308 power went from about 180fpe out of a 24″ to 220fpe from a 32″ and thats with an oversized but otherwise similar valve as the condors
stock is like 60 fpe right…add a 30″ i would say 70-75 fpe
but i would hate to be hunting with a 32″ barrel, maybe if sitting in a treestand but lugging it around the woods through bushes etc…
benchresting it is no probem though, and thanks to tank that can be removed you can actually fit it in a lot of gun cases
80 GRIT,
U.S. Men are used to a 24″ barrel on a rifle so suppose we add 10″ and make it Bullpup with 34″ barrel.
About what increase in FPE would that make ❓
yeah X, I suppose you have to primarily consider cost effectiveness…add to that the fact that not many people are going to want to carry around broom handles for rifles.
The general rule of thumb is 10 fps gain for every inch of barrel.
So considering the max output of a “tuned” condor say with a 95 gram hammer, stock spring, ported high flow valve, etc…what would the “ideal” length barrel be before it became negligible (strictly rhetorical, not for practical application…) to utilize all the potential of that amount of air exiting the valve? Perhaps another 10 inches?
@ Cy How much more power per inch are we talking? Whats the max usable length of the barrel that still makes sense?
PFFFFT…they just took a barrel of decent quality, at a length that is easy to come by which would make it cheaper.
if you stuff a longer barrel in a condor you will get more power
I have one of Tony’s 90’s as well. I have experienced those “eye puffs” numerous times while going through my 22xx building phase.
This post has made me wonder what the ideal barrel length and valve set up would truly be in any given pcp? For instance, I know many of the big bore rifles producing power tend to be “broom sticks”, so out of curiosity any guesses what the “ideal” barrel length would be for a stock high flow condor? I am assuming airfoce did their homework when coming up with the 24″ LW…but you know what they say about assuming.
…
80 GRIT,
Your explanation is much better than mine and probably the most often encountered.
I neglected to consider that while trying to reason out RCs very good explanation of gas expansion being overcome by friction.
Dang, I got caught thinking out loud again.
However my thinking about o-ring blowby would be true on occasion when breech and/or valve stem o-rings begin to fail under high pressures or just plain wear. TalonTunes o-ring mods took care of a weak original equipment o-ring problem that would often show up as a puff of air in the face and inconsistent shot strings.
I thought the increasing FPS on the “climb” was simply due to the hammer gaining ground on the fill pressure in the tank by slowly overcoming “valve lock” with the passing of each shot (the decrease of fill pressure) and when perfect harmony between hammer spring, hammer, valve, and fill pressure is achieved…you get the “meat” of the curve. Wouldn’t the fact that there is a higher starting pressure in the tank and not enough hammer strike, i.e. lower fps in the beginning slope of the curve, produce less pressure on the breech o-rings and no potential for blowyby????
my ruger mk3 pistol shoots faster with more power, than my tc R55 rifle shooting the same .22lr ammo, except for the super high speed stuff
in springers the energy is produced in the very first few inches of the barrel, something like in 2-6″ the rest of the lenght of barrel is used to stabilize gun, lower pressure in barrel, have long enough barrel to cock it..control vibrations etc….
a pcp can have both too much air, and too little…a buddy of mine was messing with a b50, and he wanted to figure out at what lenght the rifle would do best…so with a crosman 24″ barrel he started to cut it and found 14″ was where speed would suffer…he then started to cut a LW barrel in the same gun and found accuracy/groups to open up once it got shorter than 18″ i believe he was messing with a .177 setup around 20 fpe
Doesn’t a Tommy gun use a 45acp cartridge?
They don’t go that fast in the first place right?
It would certainly explain the increase in velocity if the barrel was shortened from 18″ to 16″… 😉
*edit* fully read RC’s post. He’s got it covered…. As usual. 😀
Thanks for the answers guys.
Lurker,
No I don’t think your wrong.
I was addressing firearms and for firearms it applies of course.
And it does somewhat in air guns, you can do the same thing with a longer barrel in relationship to the pressure of the charge of gas.
However, gas or air can out run the bullet and effect stability, which is why target shooters use air trippers and air guns ofter shoot better with a LDC which simply is a air stripper that reduces muzzle blast.
RC
How it relates to tuning a PCP,…..I DON’T KNOW. but;
For maximum accurate shot count we tune an unregulated PCP to achieve what we call the inverted bathtub curve. I would think there would be some kind comparison or relationship between an unregulated PCP as the tank pressure decreases compared to the decrease in length of a PB.
When the optimum Fill PSI is found for a particular pellet in the unregulated PCP, we get a few shots with increasing FPS followed by a relatively constant FPS for a good number of shots, followed by decreasing FPS at the end of our useful curve.
So, it appears that the longer barrel of the PB may have reached a magical point when pressure is nolonger adequate to overcome friction.
Ooooooh, so RC is correct and my thinking that excess pressure in the PCP was somehow surrounding the exiting pettel causing turbulence and slowing the pellet was WRONG ❗
SO, the increasing FPS on the beginning slope of the inverted bathtub curve must not have anything to do with the exiting pellet but is actually the effect of excessive pressure causing BLOWBY at the breech o-rings.
THANKS RC, and thanks for the question Lifo2001.
Damn, I think I’ll go change my breech o-rings ❗
You can at times increase veleocity in a 22 by shortening the barrel, if the original barrel was longer and the gas expansion from the firing cartridge has reached its maximun.
When that happens the longer barrel creates friction and the pressure having peaked has dropped off resulting in a slower bullet.
By shortening the barrel slightly, you catch that gas expansion/friction ratio at its peak, meaning the peak of the gas pressure and then get an increase in velocity.
Now the 45 acp has a very small volume compared to the bore,much like a 22 short capacity, so when that gass has peaked, in lets say 16 inches, but you have 18 inch barrel, you couald in fact gain velocity by cutting the barrel back to where it peaks.
This is a only the case in samll capacityty cases with a large bore area in relation to that small case capacity.
Regards,
Roachcreek
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U.S. Men are used to a 24″ barrel on a rifle so suppose we add 10″ and make it Bullpup with 34″ barrel.
About what increase in FPE would that make ❓
go to a fpe calculator and just type in your pellet weight and your current speed and whatever your fpe is…recalculate by adding 100 fps and you’ll get a rough idea.