Toning AND Tuning Your Airgun with DonnyFL Suppressors - Part II

Toning AND Tuning Your Airgun with DonnyFL Suppressors - Part II

So in my previous post I talked about the difference between decibels and tone of airgun suppressors and the concept of perceived sound or "quietness". If you look through the online forums and FB Groups, you will also hear a lot of airgunners claim DonnyFL suppressors can also help increase accuracy.

Now that is a big claim and throughout the years of airgun technological innovations we have seen those claims made by the use of all different kinds of devices. Air strippers, internal shroud bafflers, etc. My good buddy PJ over at Wisconsin Airgunners even did an entire case study going through all the different DonnyFL suppressors he had on hand. In his results he showed the differing sizes of groups he was getting and there was indeed a difference. I went out this weekend and took his research and sprinkled in some of my own findings.

A little back story first.... I too have seen accuracy changes using DonnyFL suppressors while shooting big bore airguns with my AirForce Texans over the last few years. I did this testing through swapping out the .45 cal Ronin to the Emperor suppressor and then adding the DonnyFL chamber extension to each to see what kind of shot report reduction I was getting, but I was also seeing accuracy differences in these tests.

#1 The Ronin and Emperor and Chamber Extension ALL did a great job making the Texans WAAAAAY quieter
#2 What I stumbled on was something even more interesting that needed to be explored even more. HARMONIC DAMPENING!

With the long 34 inch barrels used in all the full sized Texans, I struggled with the "whippy-ness" for the first year or so shooting with this platform, but when I learned to stop trying to TAME that whip and TIME (TUNE) it instead, I found it much easier to shoot relatively good groups at long range with a gun that was really meant to be a tool for big game hunting. There were a lot of other things I learned to control to get the accuracy I was seeking like constant velocities through external air pressure regulation, but that is an entirely different topic.

So basically what I realized by adding a DonnyFL to the end of ANY barrel of ANY airgun, you are increasing the mass of that barrel and changing the harmonic signature or your airgun. The biggest factors that define the harmonic signature of your barrel are the mass and the stiffness of your barrel. This is why you see PRS and ELR powder burner shooters using large bull barrels. These thick barrels are creating lower amplitudes, but have higher harmonic frequencies which lessons extreme deviations or spread of those "flyers".

Mathematically speaking, you can calculate the frequency of the first accuracy node of your airgun by using the square-root of the barrel stiffness divided by the mass. So by adding a DonnyFL Suppressor, you are lowering the frequency of vibration of the barrel creating a dampening effect.
Why can't we just mathematically calculate how much weight to add to the end of our airguns to find that perfect node through measurement? Because the vibrations and amplitudes / frequencies of those vibrations are so small and unmeasurable, the only way to measure them is literally the "shoot and see" approach.

Even smaller caliber and more precision focused air rifles like the FX Airguns are going to 700mm and even 800mm barrel systems (.35 barrel kit) to eeeeek out every bit of "FREE" velocity gains you can achieve through longer barrels. With that approach we run into that whip-iness that you can either try to TAME or TIME (TUNE) or a little combination of both.

In my testing the last few weeks I have been testing the carbon fiber shroud tensioning approach demonstrated by Earnest Rowe and as far as TAMING the whip of my 700mm barrel on the FX Maverick (or any other FX platform), it does a great job. But what this mod is really doing is lowering the amplitude of the barrel's harmonic signature and at the same time increasing the harmonic frequency (vibrating faster) since it is now stiffer. Much like how the PRS / ELR crowd approach the use of heavy large diameter bull barrels.

What I have found is the carbon fiber tensioning approach is getting rid of some of those flyers or at least minimizing them. To be perfectly honest though, the accuracy of the FX Maverick was great right out of the box without even messing with it. I am just chasing sub MOA groups at 100 yards and will try anything and everything to get there.

This weekend I decided to take this test to the next level and replicate PJ's case study with differing DonnyFL suppressors. Though my testing with the AirForce Texan 34 inch barrels I have found what is creating the actual end result of tighter groups by adding a suppressor has less to do with any kind of air stripping effect (which I do think exists), but has a lot more to do with the fact that you may have stumbled upon a good accuracy node. I have found that by just threading on a DonnyFL suppressor as compared to not shooting with one, all of my airguns start shooting tighter groups.

So yes - just by adding a suppressor to your airgun will increase the mass of the barrel and create the dampening effect giving you tighter groups, but can we even go a step further and even precisely TUNE to a specific projectile by changing which DonnyFL suppressor we use on our airgun. The answer? 100% YES!

In my testing this weekend I took my FX Maverick, still untouched as sent to me from FX USA for testing set at 145 bar and whatever hammer / spring tension they had it set to for the Compact. The only thing I have done with this gun is put on the longer 700mm barrel kit. In my previous video shooting NSA 36.2 grain slugs, I will call this an MOA shooting airgun with slugs straight from the factory.

But I have struggled to get the FX Hybrids to get this level of accuracy at 100 yards. I am slinging these right at 1000 FPS with this reg and hammer spring setting with the 700mm barrel. Without ANY DonnyFL, I am shooting 1.75 to 2 inch groups at 100 yards. I could try harmonically tuning the gun by messing with the power wheel or regulator and hammer spring tension to lower the velocity, but for this test I wanted to show that we can find a harmonic node by just changing the size of DonnyFL I was using.
I shot 5 shot groups using the following DonnyFL Suppressors with their weight specs and the resulting group size at 50 yards:
RONIN - 10.4 oz - 1.45 inch group
KOI - 4.7 oz - .1.3 inch group
TATSU - 4.1 oz - .52 inch group
TANTO - 3.9 oz - .76 inch group
So there it is, for my FX Maverick I now know that the TATSU at 4.1 oz is harmonically TUNING this barrel to MOA accuracy shooting at 1000 FPS with this specific regulated pressure and hammer spring set up with the Powerwheel at 7.
It is quite interesting to see that just by changing the weight by a few ounces or even a fraction of an ounce and length of suppressor you can change the harmonics of your airgun.

It is important to remember the moment I touch ANYTHING in my tune like the regulated pressure or the power wheel or the hammer / spring tension these results will change. That is why you harmonically tune your airgun to how you have it set up by using differing velocities. Changing the velocity of your airgun also changes the harmonic signature at that pressure, hammer spring, power wheel, and resulting velocity.

Furthermore it is important to note that when you change anything on your airgun, this will also change its harmonic signature. This includes bipods, adjustable buttstocks, cheek risers, monopods, rail extenders, even the torque spec of every single bolt has in your airgun. It all makes even the slightest harmonic signature changes which will require that you re-tune your gun. Sometimes you get lucky that you are still at or close to a harmonic accuracy node when you add that stuff and no changes need to be made, but again we are talking about the holy grail of ultimate precision here.

I invite you to go out and run your own tests and discover the wonder of harmonics and proving DonnyFL suppressors aren't just barrel bling. IT IS SCIENCE!
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