.222/223 is the best caliber for bullet shooters on a budget!

[scion19801]

BOb...got some more numbers:
stock gauntlet in .22 (14.3 grain) lead pellets, achieving 60 shots, 900 fps, at 1100 psi. 25.89 FPE
stock gauntlet in .25 (24.35 gr) lead pellets, achieving 24 shots, 890 fps, at 1900 psi. 45 FPE

both as far as i can determine have the same barrel length at 24"
 i know there are formulas out there to figure this out, but can find it for some reason. i know with the barrel swap i don't expect to get the 60 shots off 13 cu. in. bottle filled to 3000 psi. If i could be 30 shots( 3 x 10 shot mags) would be nice. What would my power look like?

[scion19801]

I think I got it now.
.224______________
Barrel volume is 8.921238137 @ 24"
A= .371718255
F= 780.6083355
P= 1,561.216671
.25_______________
Barrel volume is 9.424777961 @ 24"
A= .392699081
F= 824.6680716
P= 1,649.336143

.224 port sizes
.156 =57.63
.172 =63.55
.188 =69.46
.203 =75

.25 port sizes
.156 =64.32
.172 =70.92
.188 =77.52
.203 =83.70

.25 using 1100 psi to shoot 24 shots @45 fpe is 1,080 fpe. Giving 1.0944 fpe/ci.
So my guess is the stock gauntlet has wicked small porting probably. Due to low fpe. Or is there just that much loss in the system. Once mine is back. I'll be looking at the port sizes for a more accurate picture.

Bob how did you make the drop block on your 6mm? It looks like it may be a 2 piece setup? If I increase my plenum using a new lower tube, that would be cool to turn the bottle around to give it better rearward balance.

[Scotchmo]

First time I have seen a mould for CB (conical ball) .22 rimfire ammo....

It is certainly possible to duplicate the performance of a .22LR target load, my .224 Hayabusa does that at 3000 psi.... 1077 fps with a 41.3 gr. swaged RWS bullet....
...

They most often use a 15" twist Hornet barrel....

Bob

For the first barrel I'm making to replace the factory Crossman .22 barrel, I have an FX 700mm x .22 airgun liner with a 1:15 twist.

[rsterne]

Tank block is made in one piece....



Scott, that should be a good choice for a barrel, but you will likely need to size your slugs....

Bob

[Rallyshark]

First time I have seen a mould for CB (conical ball) .22 rimfire ammo....

It is certainly possible to duplicate the performance of a .22LR target load, my .224 Hayabusa does that at 3000 psi.... 1077 fps with a 41.3 gr. swaged RWS bullet....
...

They most often use a 15" twist Hornet barrel....

Bob

For the first barrel I'm making to replace the factory Crossman .22 barrel, I have an FX 700mm x .22 airgun liner with a 1:15 twist.

I just got through building a barrel off a 700mm slug liner.  It will most certainly help in the power department, and the weight will be low too

[scion19801]

Bob that is a Beautiful piece you made. What aluminium spec was used on that?

[rsterne]

6061-T6.... Mounting it offset far enough in the 4-jaw to turn the spigot that fits into the tube was a bit "hairy".... definitely some pucker factor there, especially when you start....

Bob

[darkcharisma]

Scott Did you make that mold? That’s a beautiful mould! I want one.

Dan. if I remember correctly. The gauntlet 25 cal can get up to 95fpe. I haven’t done it myself but SouthernGunner has. And it doesn’t look like he added plenums. So it’s actually 24cc for the gauntlet. I don’t know how many shots he can get off at 95fpe. Or what mods he has done to get there.

I have built a .224 regulated marauder with 80cc plenum. The highest I have tested it to was 1009fps with 39grain slugs at 2700 psi. It has a Cothran valve and super strong hammer springs so its consuming air like no other.

[scion19801]

Duy; That's insane...95 FPE with the gauntlet. thanks for the plenum size. i was sure i read it being 25cc. gonna have to ask what souther gunner did to it.

Bob; reading you articles and doing some calculations. Barrel volume is tripping me up. (c2xPi/4xL )=V barrel volume in cubic inches.
that gives me 9.424777961 for 24" .25 barrel. and 9.47881552 for 25.5" .224 barrel. in you article you mention that a 48".25 barrel is 30cc, as well as a 12" .50 barrel, using 3000psi. How did you figure the cc's out?

so if my math is correct:
using .156 ports at 1900 psi with 24" barrel
.25 cal would get 58.60 FPE
.224 cal would get 52.15 FPE but at 2100 psi its 57.63 FPE
granted theses are theoretical numbers, but just trying to get a better understanding and make sure my numbers are on track.

[rsterne]

1 CI = 16.4 cc.... Do yourself a favour and don't use so many decimal points.... I don't know where you got your volumes from, 1.18 CI for the 24" .25 cal, and 1.00 CI for the 25.5" .224 cal, are the volumes in CI....

A 48" long .25 cal barrel is 2.36 CI, which is 38.6 cc (don't know where the 30 cc came from)…. and a 12" long .50 cal barrel is exactly the same volume....

Your FPE numbers look OK.... Remember, that method (multiplying the caliber by the smallest port size and then by PI/4) is only for predicting the maximum FPE, and it's only an approximation.... You can multiply that result by the pressure and then by the barrel length / 24 to find your "lofty goal".... Remember, that is almost never achieved, even for a single, maximum power shot.... I have only approached within about 10% of that goal, at a velocity of 950 fps (pellet weight is 1/2 the FPE)…. If you use a heavy pellet at lower velocity, it is easier.... However, once you drop down to a realistic tune (so it's not an air hog), you won't achieve that goal....

Bob

[scion19801]

very true, BOB. yes my numbers were in CI.
i got the 30CC from the article you put out. just before the end out this https://hardairmagazine.com/ham-columns/how-to-obtain-the-maximum-power-from-a-pcp-air-rifle/. last picture in it.
 one last thing. (i hope, lol) is there a way to figure out barrel length?
basically, a 24" .25 cal barrel is 1.18 ci (19.3 cc) using its barrel volume, what would the formulae be to figure out how long a .224 barrel should be to match as closely as possible the .25 cal volume?

MAybe i messed up the barrel volume calculation V=(C2xPI/4xL) v= volume in cu in.
.25 squared x 3.14 / 4 x 24 =
 .5 x 3.14 / 4 x 24 =
 1.57 / 4 x 24 =
 0.3925 x 24 =
 9.42

[Scotchmo]

Scott Did you make that mold? That’s a beautiful mould! I want one.

Dan. if I remember correctly. The gauntlet 25 cal can get up to 95fpe. I haven’t done it myself but SouthernGunner has. And it doesn’t look like he added plenums. So it’s actually 24cc for the gauntlet. I don’t know how many shots he can get off at 95fpe. Or what mods he has done to get there.

I have built a .224 regulated marauder with 80cc plenum. The highest I have tested it to was 1009fps with 39grain slugs at 2700 psi. It has a Cothran valve and super strong hammer springs so its consuming air like no other.

I did not make the mold. And I have not tested these bullets in an airgun. They are designed to fit in a 22lr case. Yhey may not be optimal for an airgun. The middle of the body is .222" OD and the tail is .200" OD.

http://22lrreloader.com/design-details/

[rsterne]

The 30 cc was a goof....  …. I started talking about a .22 cal, 24" which was 15 cc, then I changed horses mid stream for the comparison between .25 cal and .50 cal and forgot to change the caption.... Me bad !!!

.25 squared is 0.0625, not 0.5....  …. That makes us even, no?.... 

To get the same barrel volume in a .224 cal as a 24" barrel in .25 cal you would take 24" x (.25^2 / .224^2) = 29.9"....

Bob

[Scotchmo]

.... Remember, that method (multiplying the caliber by the smallest port size and then by PI/4) is only for predicting the maximum FPE, and it's only an approximation....

Some more to think about:

Port area directly affects power, not energy. If you cut the port area in half, you can get the same FPE by increasing the pellet mass by 16x (assuming sufficient valve dwell , 4x).

For any given pressure:
Port_area determines maximum power (horsepower, ft-lb/s, KW, etc.). Barrel_volume determines FPE (energy, ft-lb). Knowing power, you need a time multiple in order to determine FPE. For any given power, a heavy projectile takes more time to move down the barrel. More time gives more FPE.

A full port .22 caliber at 3000psi can produce about 280 horsepower. A 0.11" diameter port will produce about 70 horsepower. (assuming 100% efficiency).

A .22 caliber with a .11" diameter port should shoot a 160gr projectile with about the the same FPE as a full port .22 with a 10gr projectile.

[rsterne]

While that analysis may be correct, my "lofty goal" formula is intended to give some indication of what the maximum FPE you might expect when the projectile is moving at 950 fps (and hence FPE = twice the projectile weight in grains)…. The correlation to transfer port size (and hence flow rate) was only to give a rough idea of how it affects "normal" PCP operation, again with that velocity in mind....

At the limit, the maximum possible FPE is still dependent on bore volume and pressure.... The percentage of that you can achieve will depend on the ratio of projectile mass to the air mass (and other losses).... For a given barrel length and pressure, the air mass is approximately constant (though the length of time to move that mass through the port may vary with projectile mass)…. For a 24" barrel of .224 cal, full of air at 3000 psi, that is about 57 gr.... So, in fact, a 160 gr. projectile should end up with significantly more FPE than a 10 gr. one, in the real world.... How that works out if the 160 gr. projectile is operating with a 0.11" port at 3000 psi in a .22 cal, 24" barrel is beyond my ability to calculate.... and so far away from what I might actually try and build, is beyond my interest as well....

Bob

[scion19801]

The 30 cc was a goof....  …. I started talking about a .22 cal, 24" which was 15 cc, then I changed horses mid stream for the comparison between .25 cal and .50 cal and forgot to change the caption.... Me bad !!!

.25 squared is 0.0625, not 0.5....  …. That makes us even, no?.... 

To get the same barrel volume in a .224 cal as a 24" barrel in .25 cal you would take 24" x (.25^2 / .224^2) = 29.9"....

Bob

Got it now Bob. No harm no foul. Plus I was using square root vs square. Numbers look way better now. Lol

[Scotchmo]

".... Remember, that method (multiplying the caliber by the smallest port size and then by PI/4) is only for predicting the maximum FPE, and it's only an approximation...."

...formula is intended to give some indication of what the maximum FPE you might expect when the projectile is moving at 950 fps...

OK - for a constant (or relatively constant) velocity (950fps in your case), that is true.

Each of these gets total FPE:
FPE = pressure x barrel_volume (this is NOT affected by port size or pellet mass)
FPE = mass_flow_rate x time (this is affected by port size and pellet mass)

Typically, my design parameters are based on desired projectile and desired velocity. With that I can design (on paper/computer) what is needed to achieve that before actually building it.

It works well with PCP powerplants.

I tried it with piston guns but it is more complicated.

[rsterne]

Scott, please forgive my post above, I did not mean to sound condescending.... Chalk it up to being tired.... You obviously have spent a fair amount of time working out a formula for horsepower based on port area, and the relationship to projectile weight.... We know from empirical data that the FPE is roughly proportional to the smallest port diameter (not area)…. but this should be applied at about 950 fps (ie constant velocity)…. If the velocity is constant, then the projectile weight must be proportional to the FPE, and at 950 fps, it would be 1/2 gr. per FPE.... Further, if the pressure, barrel length and caliber are all constant, then the average velocity, and hence the acceleration, must be virtually constant as well.... and since we are talking about a maximum power shot, the valve is open until the projectile leaves the barrel.... For simplicity, let us assume an infinite reservoir, so constant pressure at the valve seat....

You state that the horsepower is proportional to the port area, which is the square of the diameter.... If the air is accelerating a projectile whose weight is proportional to the port diameter, can you mathematically prove that the muzzle velocity should remain a constant?.... If you can do that, then we have our answer as to why the FPE is proportional to the port diameter, rather than the port area.... ie the math to back up the observations....

Bob

[scion19801]

Awesome. thanks for helping get this straight Bob. Spreadsheet looks way better now. And i reduced the decimals.

Scotchmo

FPE = mass_flow_rate x time (this is affected by port size and pellet mass)

do you have a formula for your findings with this?

[Scotchmo]

Awesome. thanks for helping get this straight Bob. Spreadsheet looks way better now. And i reduced the decimals.

Scotchmo

FPE = mass_flow_rate x time (this is affected by port size and pellet mass)

do you have a formula for your findings with this?

That's a poor example on my part. It's not "findings". This is all at a preset pressure. Maybe I should have said "proportional to" and not "=".

Knowing the pressure, you can find the density of the HPA. If you know the mass flow rate, and the density of the HPA, you can calculate the volumetric flow rate. Knowing the volumetric flow rate and pressure, you get power:
http://www.metaris.com/hp-calculator.php

Multiply power x time and you get energy, which should translate into kinetic energy of the pellet+air.