What’s the most power possible from an Impact?

215 FPE that's only in your dreams.

I think 120 - 140 fpe is possible. 

I think 120 would be pushing the limit.

I will eventually give an idea of the limits for the .25 once I get my rifle back. I am still waiting to get it after several months, won't go into why here but I am having a TJ's un-choked barrel fitted. I have the extra high power Huma and will get all the available power mods, some I already have and waiting. And I run on HELIUM. If that doesn't get me near the threshold of what is possible, I don't know what will.

I run on HELIUM. If that doesn't get me near the threshold of what is possible, I don't know what will.

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How do you get the helium up to 250bar? How do you buy the helium and how much does it cost?

Got 111fpe

after over 1k of testing its more consistent at 101-103 fpe with 25 shots 250-170b fill.

no slugs tested only JSB .30 pellets 

50.1gn at 965fps

44gn at 1015fps

700mm .30 STX

reg at 165b

with alot of mods, there are five 100 FPE impact out for extersive testing.

most suprizing is the 44gn accuracy over 1000fps don’t know if its just my barrel but I can group clover size at 50y about 1” in vary windy conditions at 75y with 50gn is about 1/2” at 50y

if shot over 110fpe shot count drop to 18-20 shots I prefer 2 full mag shot count with OEM mag.

other caliber tested.

.25 700mm 34g 1024fps

.22 700mm 25g 1030fps

18g .22 700mm 1165fps

11gn .22 700mm GTO 1325 fps

40gn .22 700mm slug 895fps, this slug has the accuracy of a pellet.



please don’t ask What/where/when till testing is complete, 

I get the helium from Roberts Oxygen, a welding supply company. Rental on the 6K tank (that's 6,000 psi) is separate from the helium cost. I just paid the annual rental and it was $154 I think. Re filling was $122 the last time filled it. Once the 6K tank gets below 4500 psi I run the helium through a shoe box booster pump into a Great White tank. The 6K tank weighs 290lbs., lets just call it 300. So you can see that moving it around is not going to be something you want to do on a regular basis. I've been toying with the idea of getting a few of those 3,000 psi scuba tanks that I could move around a little easier. That way I could fill the scuba tanks and then use them to fill the 4,500psi carbon fiber tanks. I would need an in line regulator though to supply the shoe box from the scuba since it can only take a 120psi supply pressure. You could of course get one of the party balloon tanks and do the same thing with an in line regulator if the pressure is above 120-125, assuming you could make some adapters for the threads. But my guess is that you would be draining those type of tanks rather quickly and would want to go to the 6K. I made a https://www.youtube.com/watch?v=U7Jf_dlTsS4 last year for someone who PM'd me, I should make it over because of some mistakes I made but it will give you the basics. If you want the follow up video's I can provide a link for those too.

Theoretically with a 700mm barrel and a 30 cal, an fx impact with proper full bore porting could achieve 150 + FPE with a 90 gr projectile at 150 bar....this would ideally have at least 1/2 CC of plenum per FPE (75 cc of plenum) to achieve this...although 1/3rd MAY do the job as well (50~ cc's)...



Take it a step further, and run a highly customized rig that is regulated @ 3k (not sure if its even possible, this is THEORETICAL HERE...)

The same configuration @ 3k would yield around 200 FPE with a 110~ gr projectile...

Theoretically with a 700mm barrel and a 30 cal, an fx impact with proper full bore porting could achieve 150 + FPE with a 90 gr projectile at 150 bar....this would ideally have at least 1/2 CC of plenum per FPE (75 cc of plenum) to achieve this...although 1/3rd MAY do the job as well (50~ cc's)...



Take it a step further, and run a highly customized rig that is regulated @ 3k (not sure if its even possible, this is THEORETICAL HERE...)

The same configuration @ 3k would yield around 200 FPE with a 110~ gr projectile...

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sorry Ackuric. I,m not good at all with calculations on paper to get results, I mostly machine parts or mods the OEM parts to see the actual results and go from there and could takes days or even weeks in trial and error. here is a photos of all the mods parts for the 100FPE + impact using no more then 165b any higher reg pressure than that I have trip the threads on the rod on both ends.

I have dual porting on the pellet probe and barrel and that resulted in 12fps more than the full porting as you stated,

on the plenum tube I started with 90cc then Gradually filled the the tube till the FPS stated to drop at 30cc and that was the finial length instead 90cc that would hang down lower then the butt and pistol grip ---it look really ugly to look at.

please let's team up to get 200 FPE because I dont think its possible, can you show me your custom parts to enlighten me ?

wrong thread *edit*



Ernest, please don't take any thing I say as an insult to your work or the restricted or limited confines the platform may have, as I have never been hands on with it...I assure you the numbers I provided are within the realm of possibility but I also clearly state its just in theory provided few criteria are met...



Making an FX run FULL bore would require lots of customization, from retracting bolt probe, to adequate valve seat and poppet geometry, modified spring/hammer rating, I am in no way saying its easy, but certainly should be possible...Short of making the bolt probe retract during its firing cycle, you can still generally remove enough material from a custom probe to allow upwards of 90% bore porting. A 90% bore ported .30 cal with 700mm barrel at 150 bar should yield roughly 130 FPE off a 68 gr projectile....add in an extra 15 bar and that same configuration SHOULD yield just shy of 150 FPE with 80 gr's flying nearly around 900 FPS.



Now if the valve seat to pellet base distance on the fx impact is extraordinarily large compared to other platforms such as the crown, or streamline, then those platforms would be much better suited for the above theoretical energy outputs. HTH

FWIW anything beyond 80-85% porting should be oblong in the barrel to allow ammo to safely load without damage. The width should never exceed 85% IMO, 80% being even safer. That is why I hold a fairly firm position that 80-85% bore porting should be bare minimum on a regulated actioned rifle, as this will vastly improve its performance. Choking off the flow while going bigger and bigger on bore size is counter intuitive.

Thank you Ernest. I much prefer actual testing and results like you're giving us.

It's a great time to own and shoot an FX!

FWIW anything beyond 80-85% porting should be oblong in the barrel to allow ammo to safely load without damage. The width should never exceed 85% IMO, 80% being even safer. That is why I hold a fairly firm position that 80-85% bore porting should be bare minimum on a regulated actioned rifle, as this will vastly improve its performance. Choking off the flow while going bigger and bigger on bore size is counter intuitive.

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FWIW anything beyond 80-85% porting should be oblong in the barrel to allow ammo to safely load without damage. The width should never exceed 85% IMO, 80% being even safer. That is why I hold a fairly firm position that 80-85% bore porting should be bare minimum on a regulated actioned rifle, as this will vastly improve its performance. Choking off the flow while going bigger and bigger on bore size is counter intuitive.

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Ackuric, to get more speed beyond 85% single oblong porting is to have dual porting with same size hole the OD of the porting is 3-4mm smaller to channel the air flow to the 2nd porting on the barrel while the 2nd porting on the probe is controlled by the size of the hole -- I start out with a 3mm porting and slowly enlarge the porting till I get the max speed till the next larger porting reduce the speed, now I get a new prod and drill the proper size 2nd porting, this way it won't be counter intuitive as you stated.

your theory / calculations are so misleading me and others, I'm not learning anything without actual testing, please PM me so we can talk and have a clear understanding to help this forum. 

Ackuric, to get more speed beyond 85% single oblong porting is to have dual porting with same size hole the OD of the porting is 3-4mm smaller to channel the air flow to the 2nd porting on the barrel while the 2nd porting on the probe is controlled by the size of the hole -- I start out with a 3mm porting and slowly enlarge the porting till I get the max speed till the next larger porting reduce the speed, now I get a new prod and drill the proper size 2nd porting, this way it won't be counter intuitive as you stated.

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The barrel transfer port on a .30 Impact measures 7.1mm right out of the box so that would be 92% would it not? The valve seat and pellet probe are much smaller so it seems they would be the greatest restriction.

Thank you for your advise.

My calculations are just physics based, Energy output = X Pressure along Y Barrel length and Bore diameter, with Z Pellet weight is in a nutshell how I theorize or calculate performance of an air rifle. Physics isn't biased to brand names like some believe, rifle configuration and other variables do come into play...To be absolutely precise you need to consider other variables such as Valve seat to Pellet base volume, Mass of air ejected, Pellet break force, Pellet friction, but all the latter variables are not as important as the former, so I generally deduct a standard amount to simplify the formula as many people wouldn't know how to calculate all the micro variables I just mentioned...among many others.



In a pressurized system, one big intake/exhaust is better than 2 smaller ones of equal size, its not like a car engine where you potentially have 2 heads and its better for each head to have separate exhaust systems due to the nature of the design and their pulses not being equalized, a pcp system has 1 valve and is best suited to have 1 intake/exhaust port. The highest powered air rifles (3000 fpe+ 20mm air rifle..) that I have ever learned about abide by this concept and generally port their system with 1 intake and 1 exhaust that is larger than the bores porting. 



Its a tried and true system, allow the pathway for air to flow as close to equivalent to bore diameter or greater, and you'll achieve maximum energy output in that configuration provided you have enough plenum and air to shove down the barrel...anything under than bore size porting is a 'choked' system that limits potential energy output.



The squarest pressure wave possible is provided by a single outlet equal or greater than bore diameter...there is no argument that this configuration provides the highest energy output. The shortest distance traveled from valve seat to pellet base will increase this marginally, thats why Air force direct valves out perform many other competitors in energy output side by side with similar configurations other than valve placement. HTH..



-Matt

Ackuric, to get more speed beyond 85% single oblong porting is to have dual porting with same size hole the OD of the porting is 3-4mm smaller to channel the air flow to the 2nd porting on the barrel while the 2nd porting on the probe is controlled by the size of the hole -- I start out with a 3mm porting and slowly enlarge the porting till I get the max speed till the next larger porting reduce the speed, now I get a new prod and drill the proper size 2nd porting, this way it won't be counter intuitive as you stated.

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The barrel transfer port on a .30 Impact measures 7.1mm right out of the box so that would be 92% would it not? The valve seat and pellet probe are much smaller so it seems they would be the greatest restriction.

Thank you for your advise.

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If thats correct then that is correct, I was mistaken and mislead by assuming their valve seats were all the same...if thats the case I apologize...theres no way they are only making that much power @ 92% bore porting though...something doesn't add up and is restricting airflow?


The valve seat/throat to flow that much would need to be 8mm with a 3mm valve stem, and the bolt probe's area would have to be equal to 2.54 mm in diameter of a circle...if that criteria is currently met right out of the box, then I retract a lot of what I said in regards to fx's .30 cals....but if the above is NOT true then what I said before basically stands, because the above configuration should yield roughly 150 fpe no questions asked at 150-155 bar..

https://www.pyramydair.com/s/m/AirForce_Texan_Big_Bore_Air_Rifle/3575#7497



.30 cal Air force texan @ 34" barrel and 3000 psi can make 300 fpe. What do my calculations estimate this configuration to do you ask? 290 FPE is what I calculate...and thats with a conventional valve not knowing how the direct valve effects efficiency of power output. 290/300 is 96.666% accuracy. Not shabby huh? That is without knowing all the micro variables of this particular gun!!! That is how close I can theorize power output of a configuration without knowing every variable..



My calculations are always conservative, its the same formula I used above for the 150~ fpe estimate with an impact @ 700mm barrel ect...and I guessed UNDER not over.