The Umarex air saber is my favorite arrow slinging device of any kind with or without a string, but due to its propulsion method it comes with some challenges I did not anticipate, like arrow tuning. In the following paragraphs I will do my best to explain to you how to do it and help you get those groups as tight as possible with ANY broadhead.
First thing you need to do when tuning an arrow shot from an airgun is to forget everything you know about tuning an arrow from a bow.
An arrow shot from a bow is pushed, the force created against the arrow by the string and the amount of resistance that arrow provides is what gives the arrow its speed and accuracy. Too much flex in the arrow and you’ll get erratic flight due to lack of stabilization and too stiff of an arrow will cause clearance issues on the bow also resulting in erratic flight but with an air gun the arrow isn’t pushed, it’s “pulled”.
Pulled may not be the right word but think of the arrow as a trailer and the point is the truck. When the air is forced inside the arrow the arrow takes flight from pressure directly behind the insert at the front of the arrow, this eliminates all the laws of standard archery. Archers paradox no longer exists because the arrow isn’t flexing at all, there’s no force from the back of the arrow therefore no flex.
When I realized this it started me down the path of how to tune these arrows and why we need too.
If everything we know about tuning string shot arrows is applied here it shouldn’t even work. An extremely stiff arrow with no way to shorten or lengthen it yet it will shoot any weight head without much change other than some elevation. How does that work? The answer is fletchings.
Yes all arrows have fletchings but on air propelled arrows the key is faster spin. Because the arrow isn’t flexing as it goes down range and it’s being pulled not pushed the broadhead is in full command of the arrow unless the fletchings can correct the flight. This is the case on standard arrows also but the difference is the force from the string is centered directly behind the arrow which means the force is transferred through the arrow to the head and as the arrow flexes the broad head wants to go the way of the force but in air shot arrows the arrow isn’t persuading the head in any way, it tends to go one direction and continue that direction with no consistency of the direction at all. The only way to fully stabilize an air shot arrow is with faster spin from the fletchings because lengthening or shortening the arrow does not affect the flight characteristics much at all because the spine of the arrow doesn’t matter, there’s no force behind the arrow. The arrow shaft itself is simply along for the ride, it’s not really helping or hindering the flight, so what we need is a very aggressive set of fletchings that will spin this arrow as fast as possible as soon as possible.
The speeds of these arrows from air guns is comparable to that of high end crossbows today so getting an arrow tuned to shoot at 450 fps isn’t all that difficult IF you can change the length and stiffness of the arrow but that’s not an option here so our only way to “tune” is with the fletchings.
As you likely know the arrow is fed down a shroud over the “barrel” of the gun and the arrow is propelled when the air is released inside. This makes it very fast and very accurate IF the fletchings have the time and the stiffness to stabilize the arrow flight. The reason stiffness of the vane is so important is because the resistance against the air is what stabilizes the arrow and if the vane is weak then the broad head will steer the arrow and we don’t want that.
From the best video I have taken, the average arrow from a compound bow starts fully spinning about 4-5 feet from when the arrow leaves the string. In the Air Saber that distance went to 10’ due to speed and lower profile fletching. At a speed of 450+/- FPS that leaves very little time for correction room at 20 yards. I realized this when testing and I had better groups at 40 yards than at 20 yards. Explain that? Here’s the explanation. The arrow needed more time to correct. The arrow was not stabilized well at 20 yards but by the time it got to 40 yards the vanes had done their job. What I needed was to get that spin going sooner and faster.
The fletchings of the arrow touch the inside of the barrel shroud as it leaves the shroud. This creates friction which in turn creates heat which weakens the fletchings over time. As the fletchings heat up tiny pieces will stick to the insides of the barrel shroud, just look down it you’ll see the marks, each time you shoot your vanes get a little weaker. This is not a problem really for the average guy shooting in the back yard honestly because I didn’t notice changes until around 100+ shots from each arrow.
The weakening of the vanes through loss of material and heat makes them slowly start to lose their effectiveness in correcting flight. Weak vanes taking longer to stabilize arrows explains my 40 yard groups being better than my 20 yard groups. You don’t really notice this change on the vane itself by appearance but bend it over compared to a new factory one and you’ll feel the difference.
The solution is obviously to refletch the arrows but let’s beef them up a little and see what happens. My first try was with standard 4” vanes but a little stiffer, they helped but they did weaken and eventually the same result happened. My next attempt was with stiffer Quick Spin vanes and this is when I knew I was on the right track. Even though these were a bit taller and did rub the shroud more as they left they were much stiffer and corrected flight nicely. I could see through video that the arrow was starting its spin sooner, I’d like to add here that the arrow can actually start spinning some while still in the gun, whereas a string shot arrow must be clear of the bow and string to start its spin.
Knowing that I could likely get even more spin I continued my experiments. The goal was to be able to shoot a fixed blade head at the fastest speed possible without losing the accuracy of the gun. These guns are very accurate and shooting groups usually results in broken arrows and I wanted this performance but with a heavier arrow and fixed blade head.
My next try was with extra stiff crossbow vanes and right hand helical and man did I discover something here. I was shooting my same groups at all distances with field points but when I screwed on a fixed blade head the results were surprising. I was still getting very good groups but would occasionally get a group that started to open up with certain heads. All these heads are tuned and straight and flew true and I used the same heads for each trial for consistency.
I went to a local archery shop and told the guy behind the counter what I was working on and asked if he had any extra stiff crossbow vanes but long enough that I could put a lot of helical in them. He said yes but then asked why not use lower profile extra stiff vanes and four fletch them? This was what I needed! So I went home and busted out the old Blitzenberger arrow fletcher and set it to 90 degrees and started working. It didn’t take long to realize this would be the way forward.
I actually built the first one with the stiff vanes in a three fletch configuration and a hard right helical and it worked but after 1000s of shots with all the combinations of fletchings I could find I found that the 4 fletch 4” extra stiff crossbow vanes with 1 degree of helical would control 95% of the broadheads I screwed on.
So why go to all this trouble when you can simply screw on a mechanical head and go shoot and it will be fine? Because I needed that arrow to penetrate a very large critter and failure was not an option. In fact, failure of the arrow could mean death to me or anybody in my hunting party. We were going to kill a Cape buffalo and I had to get this right.
The next obstacle was weight, again due to the arrow being pulled not pushed, adding weight was not gonna change the spine of the arrow. Adding weight to an arrow will weaken its spine because the resistance is greater against the force of the string but in this case again that doesn’t matter. The only thing we needed to worry about was our elevation and speed. What is the balance to get the greatest speed but also enough weight to carry a broadhead through a 2000 pound critter?
I started adding weight, first in the form of heavier heads but that adds surface area which adds to the job required by the vanes so I settled on arrow weights instead. Now traditionally these would be added inside the arrow in the form of an insert or something attached to the insert. That was not an option for us as we needed the back of our insert to sit against the air tube. I finally settled on a 100 grain screw in insert and a 100 grain head that screws into that. I felt the double connection points did add a point of weakness that I didn’t like but I needed to test it and see.
The heads were premium single bevel heads of 100 grains and small profile. The smaller profile will help the vanes correct sooner and the straighter the arrow enters the deeper the penetration. The combination of the Iron Will head and insert along with the stiff four fletch vanes with right helical came out to just over 500 grains. That’s a pretty respectable weight for big critters but is it enough for the biggest and toughest of critters? Most archers would say that’s not enough for buffalo and at bow speeds I’d agree but we have more power than a standard bow and therefore more speed.
I think the answer will be in our final kinetic energy measurements so we needed to check the speeds.
Now in my experience, and I’ve had 4 Air Sabers, they run about 420ish FPS from the factory with factory arrows and 100 grain mechanical heads. I’ve taken countless whitetails and hogs with this factory set up and would encourage anybody wanting to hunt deer to simply do that. The energy of the arrow more than makes up for the energy robbed by the mechanical head expanding for deer size and smaller critters. That said I’m not a fan at all of mechanical heads from standard bows and honestly not really a fan at all but having that extra power and whitetail being medium bodied animals I have no problem hunting whitetail with the air saber and mechanical heads. The standard factory arrows and vanes will give you several 100s of shots before needing reflection.
Back to our energy! The arrows came in at just over 500 grains and moving at 370-380 FPS. That’s over 100 pounds of KE which is plenty for most any critter on earth with a razor sharp fixed blade head.
So we had 200 grains up front, we had four 4” right helical vanes and we had a dead sharp cut on contact head. How does it perform?
The groups were back to “factory” size groups! I shot almost two dozen different broad heads with this arrow and the groups were outstanding. Admittedly some were better but all were very good. The vented heads were actually the worst of the groups. I have no explanation for this but it was consistent. All solid bodied heads shot great groups that I would hunt with.
The vanes of these arrows are taller and they do rub the shroud more so they didn’t last as long. I had no issue with this as I needed them for a special hunt and still was getting several dozens of shots before the groups would open up with big fixed blade heads. One thing you can do to help with this issue is use some powdered graphite in the shroud. It reduces the friction and thus the heat which both weaken vanes.
How did they perform in real life? I'd like to say flawless but what I suspected was the weak point was in fact the weakest point. My first shot with this set up was on a Rio grande turkey, I know over kill but I needed a test and he was there in season so I sent it. 34 yards and I 10 ringed him but he ran off with the arrow 20 yards before he went down. How is that even possible? How did it not pass through? How is he even walking away? It did pass through and went into the ground until only the fletching remained in the turkey. As he took flight the arrow broke at the insert threads, right where I knew the weak point was. Not happy about that at all I went back to the bench to fix this issue. I tested all kinds of things and when all was said and done after 5 more kills of hogs and deer with this set up I didn’t have a single other failure. I suspect that the arrow stuck in the dirt and the fact the turkey took off straight up put way more force on that insert than would normally occur.
The results on the buffalo were nothing less than impressive. The shot was 33 yards, the arrow entered high on the edge of the shoulder blade and stuck out the opposite side also high in the shoulder. The broadhead was just the point out of the skin and the arrow broke at the insert again. The damage was done as both lungs had holes in them but I would rather not have the insert break there. The arrow had done its job and the broad head was still in one piece after passing through two Cape buffalo shoulders, that’s very impressive.
The initial opinion of the South Africans I told about what I was doing was, “you’ll be lucky if you don’t die!!”. At the end of the week there was a whole camp full of believers. When I shot completely through their archery target and the arrow was last seen headed toward the Indian Ocean they started to pay attention.
As of right now I will say the best performing arrows from the Air Saber for the biggest of big game are 4 fletched, extra stiff 4” crossbow vanes and 200 grains up front. Try it out but fair warning, your standard archery target will not stop that arrow in most cases.
I have since shot completely through a zebra and never seen the arrow again and also through a blesbok (comparable to whitetail) with the same result.
In my opinion the best test for arrow flight on super fast arrows is at close range, you’ll learn more in 20 yards than you will at 40 or 50 because given time the fletchings will correct the flight.