Author Topic: 105 FPE TalonP  (Read 302 times)

Bullfrog

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105 FPE TalonP
« on: August 08, 2021, 06:47:29 PM »
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Bob, can you weigh in on the airgun science behind making that much power with a short barrel? The barrel is just a hair over 12".



Alan

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Re: 105 FPE TalonP
« Reply #1 on: August 09, 2021, 04:56:36 AM »
I'm not surprised at the velocity or power developed. After you have a few weeks of use out of the gun, it would be nice to see what groupings look like at the various power levels. Airforce airguns tend to be very accurate when tuned for the load in question.

The other issue, is variability of power. All too often, folks tune their airguns for the max power, rather than best accuracy and efficiency. When you need more power, you do what you did, and increase the caliber.

Good video, by the way!
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Alan

I have a Hill EC-3000 compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your tank as a courtesy (4,250 PSI limit).

rsterne

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Re: 105 FPE TalonP
« Reply #2 on: August 09, 2021, 08:15:49 AM »
I didn't view the full video, but the maximum FPE for a .30 cal with a 12" barrel will depend on the pressure, and using the small gauge on the gun (which may or may not be acccurate) he was "just over 3000 psi".... Using my "lofty goal" formula, at 3000 psi I get the following....

Bore area = (0.30^2 x PI/4) = 0.0707 sq.in.... At 3000 psi that is (0.0707 x 3000) = 212 lbs. force.... Over a 1 foot barrel length, the maximum FPE would be 212 FPE, but that includes the mass of air accelerated and all other losses.... A very good PCP could achieve half that (my lofty goal), which would be 106 FPE.... Short barrels have less air that needs to be accelerated, so can do fractionally better in some cases.... In addition, shooting a heavy (for caliber) pellet at under 950 fps means that the pellet weight is a higher percentage of the total mass, so again will allow that figure to be exceeded a bit....

105 FPE is a great result, depending on the exact pressure used....

Bob
« Last Edit: August 09, 2021, 08:43:33 AM by rsterne »
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steveoh

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Re: 105 FPE TalonP
« Reply #3 on: August 09, 2021, 12:48:59 PM »
That is mighty powerful for such a tiny little carbine.

I looked at these for a long while, but had no idea they'd make that kind of power. Nice.
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Alan

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Re: 105 FPE TalonP
« Reply #4 on: August 09, 2021, 04:38:25 PM »
Power yes! Accuracy? We're still out on that question.
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Alan

I have a Hill EC-3000 compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your tank as a courtesy (4,250 PSI limit).

Bullfrog

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Re: 105 FPE TalonP
« Reply #5 on: August 09, 2021, 07:47:49 PM »
Power yes! Accuracy? We're still out on that question.

A lot of people don’t believe me, but I’m totally convinced most accuracy problems with the Airforce guns come from the spin-loc air tank not being properly tight onto the frame. The design depends on the tank to stiffen the frame where the tank connects, otherwise the frame flexes during the shot cycle. Slightly hand tight isn’t good enough. When I figured this out I turned all of my Airforce guns into tack drivers overnight. A dab of blue loc-tite is a quick, dirty, but effective way to lock the tank down.

Bullfrog

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Re: 105 FPE TalonP
« Reply #6 on: August 09, 2021, 07:51:29 PM »
I didn't view the full video, but the maximum FPE for a .30 cal with a 12" barrel will depend on the pressure, and using the small gauge on the gun (which may or may not be acccurate) he was "just over 3000 psi".... Using my "lofty goal" formula, at 3000 psi I get the following....

Bore area = (0.30^2 x PI/4) = 0.0707 sq.in.... At 3000 psi that is (0.0707 x 3000) = 212 lbs. force.... Over a 1 foot barrel length, the maximum FPE would be 212 FPE, but that includes the mass of air accelerated and all other losses.... A very good PCP could achieve half that (my lofty goal), which would be 106 FPE.... Short barrels have less air that needs to be accelerated, so can do fractionally better in some cases.... In addition, shooting a heavy (for caliber) pellet at under 950 fps means that the pellet weight is a higher percentage of the total mass, so again will allow that figure to be exceeded a bit....

105 FPE is a great result, depending on the exact pressure used....

Bob

Thanks Bob. I can’t give an exact pressure for the 105fpe, it was likely 3100psi.

The gun really loves being set around 72fpe. Towards the end of the video I ran a shot string with 2 oring buffers on the tophat stem and I got several shots that were perfect on the low 850s. That will probably be adequate for most of hunting purposes.