Increase FPE by 70% with Helium? The AirForce Texan HE Experiment!

[UpNorthAirGunner]

Can you increase foot pounds of energy by 60-70% on your big bore air rifle for $100? Helium may be the answer! I call this the AirForce Texan HE Experiment!



I have been reading about the potential performance increases that helium can have over regular compressed air. I have seen reports of 30% and higher FPS increases which would give significant amount of additional foot pounds of energy at the point of impact on big game. I have also read arguments that the cost of helium isn't worth the performance increase (it cost $100 to fill my 75 Cubic Foot 4500 PSI tank vs. $10 for Compressed Air). So after this test you will see that increased my FPS from 880 to over 1100 FPS! That game me an additional 200 foot pounds of energy! WOW! I had also read that helium can escape past seals and potentially won't hold pressure. I tested this in my AirForce Texan .357 and after 24 hours, the helium pressure only dropped a small amount from 3000 PSI to 2950 PSI on my bottle gauge. Not bad at all.... So here is my take on this topic.

There are people out there dropping $500+ on 4500 PSI carbon fiber on-board bottles with extreme valve and heavy spring set ups to get additional power from their guns. Personally - I like to shoot a ton with my gun and like the option that I can shoot it in stock form and get 6-10 shots per fill on regular compressed air regulated at 2900 PSI. My plan is that I will keep the fill bottle of helium separate for when I want that extra power when hunting deer and just shoot stock equipment and HPA for punching paper (and golf balls). BAM! In a later test I got up to 1143 FPS! Increased FPE by 70% for $100!

[WeeHeavy]

Not sure how you're planning to store the helium long-term. If it is in a vessel intended to store compressed air, I suspect you will be loosing a fair amount past the seals due to the relative size of helium vs air (even assuming 50 PSI per day you observed in the gun, such storage would be wasteful). If you're renting or buying a tank intended to store helium, I would imagine that will get rather more expensive than most folks would find worthwhile, but I won't speculate much on what others find worthwhile. Though it is too rich for me, I'll be curious about your experience here.

[UpNorthAirGunner]

Not sure how you're planning to store the helium long-term. If it is in a vessel intended to store compressed air, I suspect you will be loosing a fair amount past the seals due to the relative size of helium vs air (even assuming 50 PSI per day you observed in the gun, such storage would be wasteful). If you're renting or buying a tank intended to store helium, I would imagine that will get rather more expensive than most folks would find worthwhile, but I won't speculate much on what others find worthwhile. Though it is too rich for me, I'll be curious about your experience here.

The carbon fiber tank I have should hold the pressure for quite a long time based on the feedback from my local Scuba shop.  They have SCBA tanks with the same seals as my carbon fiber that have been on the shelf for over a year and have held the pressure.  The seals on the actual bottle on the Texan seem to be the weakest link.  But again -if you read the post with the video, it fits my particular use case that I would only be airing up with helium during the day(s) of my hunt.  So if it is holding pressure for 24 hours on the actual gun with theoretical indefinite holding capacity on the carbon fiber fill tank - it works for how I will be using this air source for hunting applications.  For all other target shooting, I will be using regular HPA.  I guess the take away from this is you can leave your gun stock and get some pretty amazing increases for $100 (initial cost of tank fill).   I will say that I noticed my shot count went down from 6 to 3 shots per fill with Helium.   

[aluminumfetish]

Mrhollowpoint and crew have been shooting with helium for years. He talks about it in his videos fairly often. At the GTA funshoot 2 years ago a guy brought a 6000psi Nitrogen tank and that was awesome. It performed like HPA but 6000psi on tap, that was cool. He said the performance a touch better with nitrogen but not like the upgrade helium provides. I have looked into about every option of Helium and Nitrogen to fill guns. The talk size to get 6000 psi is enormous and HEAVY. Helium is similar. If you get set up with helium, please share details ?
Stay safe,
Aluminumfetish

[UpNorthAirGunner]

Mrhollowpoint and crew have been shooting with helium for years. He talks about it in his videos fairly often. At the GTA funshoot 2 years ago a guy brought a 6000psi Nitrogen tank and that was awesome. It performed like HPA but 6000psi on tap, that was cool. He said the performance a touch better with nitrogen but not like the upgrade helium provides. I have looked into about every option of Helium and Nitrogen to fill guns. The talk size to get 6000 psi is enormous and HEAVY. Helium is similar. If you get set up with helium, please share details ?
Stay safe,
Aluminumfetish

So I just opened my gun case and I stand corrected.  I thought I had lost about 50 PSI from leakage, but I think it was temperature pressure loss since it was below freezing.  I just checked it and the pressure is still sitting right at 3000 PSI after 4 days of sitting in the case in my basement.  So far the on-board bottle is holding the pressure as is the 4500 PSI 75 Cubic Foot Carbon Fiber storage tank.  What I like about this set up is that I am shooting at the manufactures stock specs of 3000 PSI.  No need for new on-board carbon fiber bottle with extreme valve or upgraded spring or hammer. Its all stock except for the chemistry of the compressed gas.   I am not sure if every air gun would have this same result with the particular seals - but so far so good for me.   In a perfect situation, I would have a small carbon fiber tank just for helium like this one: https://www.pyramydair.com/product/air-venturi-carbon-fiber-air-tank-fill-station-4500-psi-88-cu-in?a=4708 . The cost to fill that would be so cheap compared to the $100 fill for my 75 cubic foot tank.  Since I would only be using it for hunting applications that may be the route I go, but for now I have a larger 75 cubic foot tank holding helium and then I have another 100 cubic foot carbon fiber tank just for regular HPA.   

Crazy my .357 now has the hammer power of a .45 Texan, but with a CRAZY flat trajectory.  Best of both worlds now!  No more rainbow shots out to 100+ yards and a TON of carrying power into the game at impact.  Now I just need to get a buck to stand in front of me to put the smack down with this newly found extra 200 FPE!

[Techie]

Increasing velocity may not be a good thing, especially when it goes up above the speed of sound and negatively affects accuracy.

[rsterne]

Helium is well known for its ability to increase velocity and FPE.... Unfortunately, when you push the velocity beyond about 1000 fps, the drag on the bullet goes up so quickly you lose that extra velocity VERY quickly, and the wind drift actually INCREASES.... The best application is to use the extra power of Helium to drive a heavier bullet, with a superior BC.... but still keep the velocity under about 1000 fps....

Bob

[UpNorthAirGunner]

Helium is well known for its ability to increase velocity and FPE.... Unfortunately, when you push the velocity beyond about 1000 fps, the drag on the bullet goes up so quickly you lose that extra velocity VERY quickly, and the wind drift actually INCREASES.... The best application is to use the extra power of Helium to drive a heavier bullet, with a superior BC.... but still keep the velocity under about 1000 fps....

Bob

Agreed!  Now my next experiment is to match a heavier grain weight of bullet to this new increase in velocity to get it around 1000 FPS and / or use my regulator to find the PSI level to get my preferred ammo choices zipping at around 1000 FPS.  I am really liking the flattened trajectory - but having a heavier bullet in hollow point form that will actually expand at this 900+ FPS velocity is great and I will continue to report my real world findings.

[UpNorthAirGunner]

Increasing velocity may not be a good thing, especially when it goes up above the speed of sound and negatively affects accuracy.

I was thinking the same thing, but in my testing at 1000-1100 FPS-ish I was seeing an actual tightening of my groups.  Not sure if it is because of the 1:16 twist rate and 174 grain longer-ish ammo I was shooting, but this gun seems to be liking this speed increase out to 100 yards.

[cootertwo]

So, why is this? Is it because the helium molecules are smaller, more per cubic inch, or what?

[UpNorthAirGunner]

So, why is this? Is it because the helium molecules are smaller, more per cubic inch, or what?

From what I have learned - that is correct.  The time the valve is open I believe a greater volume of air is being released into the chamber since the molecule is smaller than air (which is mostly nitrogen and some oxygen).  I have been reading so much theory and conjecture and arm chair science coming from the forums, I just had to try it myself and see real world results.  All I can say is this video shows significant increase with (come to find out) no leakage so far after 4 days.  In the original post I said there was a small decrease in the bottle pressure on board the rifle, but I think that was from the cold weather and not due to it leaking out.  When I was shooting - both the gun and tank had been inside the house 70 degrees and was then shooting outside in 35 degrees.  So the pressure drop was because of the temperature variance and not leakage (I think).  The rifle has been sitting in the case in my basement now for 4 days and it is sitting right at 3000 psi on the bottle gauge and hasn't moved.  I could report back in a week and then a month, but for me that isn't testing my specific use case in that I want to use this JUST for hunting which means I can air it up that day go to the blind and be assured that it will hold pressure throughout the day.  That was my biggest concern after reading many of the posts about helium on GTA.  I have not experienced that so far - so for me at least with this gun within the first week of this experiment - all is good to go in how I want to use this performance tweak for hunting purposes. 

[rsterne]

It is not the smaller atoms (compared to air molecules) that has much effect, but rather the much lower mass of each Helium atom, compared to air.... You would be shocked at how much mass of air is expelled from the muzzle with each shot, in fact in very high power PCPs, which have long valve dwell, the air can weigh more than the bullet.... At 3000 psi, air weighs 3.68 gr/cc, while Helium only weighs 0.477 gr/cc.... A .357 cal barrel that is 34" long (like the Texan), has a volume of 55.8 cc.... so if the barrel was full of air at 3000 psi, it would contain 205 gr. of air, but only 27 gr. of Helium.... Since the gas has to be accelerated along with the bullet, you can see that more energy can be expended moving the air than the bullet.... Not so with Helium....

Bob

[UpNorthAirGunner]

It is not the smaller atoms (compared to air molecules) that has much effect, but rather the much lower mass of each Helium atom, compared to air.... You would be shocked at how much mass of air is expelled from the muzzle with each shot, in fact in very high power PCPs, which have long valve dwell, the air can weigh more than the bullet.... At 3000 psi, air weighs 3.68 gr/cc, while Helium only weighs 0.477 gr/cc.... A .357 cal barrel that is 34" long (like the Texan), has a volume of 55.8 cc.... so if the barrel was full of air at 3000 psi, it would contain 205 gr. of air, but only 27 gr. of Helium.... Since the gas has to be accelerated along with the bullet, you can see that more energy can be expended moving the air than the bullet.... Not so with Helium....

Bob

Thanks Bob! I knew you'd have a more accurate answer.  Since I am shooting at the normal 3000 PSI level, I am assuming that it isn't having any negative effect or additional strain on the valve or valve seals then - correct?  Would it be safe to say that it isn't apply more PSI within the chamber / barrel vs. normal HPA, but rather helium is just more "efficient" as propellant to move both the air and bullet out of the barrel - correct?  Just trying to get my head wrapped around "why" this is so effective in performance increase.

[aceflier]

Pretty cool! But at 50 shots per fill on my Tex with a 87cuft tank that’s $2 a shot. Ouch! If I had a way to take a Walmart He tank and run that through my altaros and boost it that would be neat!

[UpNorthAirGunner]

Increasing velocity may not be a good thing, especially when it goes up above the speed of sound and negatively affects accuracy.

True - but I am trying to get things moving around 1000fps for a few different reasons.  #1 Increased overall FPE for maximum impact on the game animal and #2 maximum expansion of the hollow point.   Below 900 FPS I have found no matter who's Hollow point I am shooting - there is little expansion.  900+ FPS I start getting some nice mushroom effects. 

Also we went out this week with the 45 Texan to the range and at 100 yards with 350 gr. bullets there was some serious drop / hold over needed to get on bullseye.  So using helium with the 45 could prove to be a winning combo as well (almost goes without saying). 

So if I can turn my .357 Texan into a 400 FPE gun and have a nice flat trajectory to target - that may be my goal through either lowering the regulated PSI with these 174 gr. Raptors or moving up to a 200+ gr. bullet and keep shooting at the full 3000 PSI.  Accuracy is first priority though as even at these increased FPE ratings - your not going to get massive hydrostatic shock like you would with a powder burner.  Just more punch through power just in case you hit a shoulder blade and need that carrying power to get through to the boiler room for swift dispatching of the animal.  So you are correct - I need to tinker with this a bit to get it from going super sonic and get it into that 1000 FPS range. 

[UpNorthAirGunner]

Pretty cool! But at 50 shots per fill on my Tex with a 87cuft tank that’s $2 a shot. Ouch! If I had a way to take a Walmart He tank and run that through my altaros and boost it that would be neat!

That is why I wish I had one of those small 90 cubic inch paintball bottles instead of this 75 Cubic Foot CF tanks.  It would be so cheap to take it to the scuba shop to be filled and it would be just for my hunting propellant.  Basically a few shots to check / adjust zero and go out to the woods for that one shot / one kill moment on a big buck / bear / elk / Chupacabra / Sasquatch - etc.  Basically not having to fill such a large volume of a tank for a shooting situation where I plan to shoot just a handful of times at best while hunting. 

If I am wanting to go out and blast away at paper or exploding AirGunDepot.com Golf Balls - I am going with cheap HPA at $10 a fill for my 75 / 100 Cubic Foot tank.  I think where this conversation gets lost in the weeds of math / and $$$ per shot is the context of intended use. 

If the use case is just a few shots for maximum impact and power on a game animal then it makes total sense - going to the range for a day of shooting - not so much.   Same scenario in the powder burner world.  I can drop $20 on a box of 5 count top shelf sabot shotgun shells for my rifled 12 gauge shotgun or 20 cents per round for cheap target shotgun shells.  After planning / obsessing / studying / dreaming about deer season opening day for 12 months every year - I will drop a little coin to make that one shot count and have the maximum impact and chance of harvesting a huge buck. 

[rsterne]

Pressure is pressure.... I see no reason that 3000 psi of Helium should be a safety concern in a PCP intended for that pressure.... In fact, you can probably dial back the hammer strike to save Helium without losing velocity.... That would be my first step in tuning it, to see how low you could dial the setting before the velocity dropped.... No sense in keeping the valve open after Elvis has left the building, you are just blowing $$$$ out the barrel doing that....

Bob

[MJP]

Well we have been shooting He for some years now, I got about 589J out of my 357 af style platform on 18" barrel, it did 387J on air. 200bar fill.
So yes the energy increase is pretty substantial.
We are in a different opinion with Bob on the speed, I'll take flatter trajectory over wind drift any day. If you can read the wind and have your holdover correct you are golden.

I have seen the same effect on couple of guns where the higher speed results tighter groups. But they have all been on tight twist rates. My 357 on 16:1 likes to shoot fast can't remember the velocity but 156gr at 589J you can do the math if you like.

No problem on gas leaking what so ever, but delrin / pom popets wil deteriorate on helium faster than on air.
Have fun shooting and do post more of your results!

Marko

Edit: checked the velocity, it was around 1119fps and 430fpe

[Randrinaz]

I appreciate the info. You guys make doing the homework so much raised. Thanks!

[VeryStableGenius]

Hey guys, I know it's an old post but just for the sake of posterity, and if I'm not mistaken, I believe the increased velocity with helium has more to do with the faster speed of sound in helium versus in HPA.

Think about it, the gas can't travel down the barrel faster than its speed of sound. If you're wondering why can we get projectiles moving faster than the speed of sound at sea level with plain old air, it's because the speed of sound increases at heightened pressures and temperatures. For the conditions seen in airguns I've seen the figure of about 1800 FPS, which makes sense to me.