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Tuning Harmonic barrel aftermarket.

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Funny that FX showed new insights by “inventing” the Harmonic Barrel on the M3 with a weight that can be adjusted by fractions of an inch where as they also sell a chronometer to be attached on to the barrel end with elastic bands without any concern about harmonics. I do see a very big improvement in the harmonic tuning of airguns with this new feature though. It remains to be checked in tests amongst us users but the idea and principe appeals to me. I sincerely hope that for other FXmodels and brands aftermarket shrouds with this feature will come to the market. I challenge barrel and moderator producers to pick the idea up and start developing with this principe. Just dial in your reg + hammerspring for desired speed with a specific pellet or slug and fine tune your grouping with the ( micro) shiftable weight...... A lot of frustration will turn into a very satisfying tuning process I think. Your thoughts ?
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Thanks for chiming in on this topic. First off, FX, nor myself, have made any claims to inventing the concept of barrel harmonic tuning or barrel harmonics in general. As a matter of fact, that claim to fame goes to the first time someone realized that if they fired their gun while resting the barrel on something (or even touching their barrel) their point of impact changed and learned not to do that. So that prize goes to someone from hundreds of years ago and is now dead and gone. Now with that said, I can fill you in on some of the background of THIS specific application and our approach. 

My history with barrel harmonics and droop and even thermal effects on barrels goes back to my time as an M1 Abrams Tank Gunner 1995-2004. I had the privilege of serving with one of the greatest Master Gunners to ever serve in the Army. - SFC John Koch I learned so much from that guy from how barrels move and shift and vibrate and all the things we would do as a crew to control those movements. Lucky for us most of it was baked in the fire control system (computer), but there were human elements we had to check to ensure our 120mm gun was spot on accurate as it was from the last time we bore sighted it and shot confirmation groups. For instance, throughout the day as the sun warmed the barrel we would have to do a Muzzle Reference System (MRS) update to bring the reticle back to the known muzzle accuracy point. The concept of barrel / platform vibrations and affecting POI shift were also a big part of our training through our tank gunnery exercises where we had our driver find a speed where the tank track would become smooth and wouldn't "chatter" for when we were engaging targets while on the move. But the physics and interest of this topic is what nudged me in this directions with airgun applications once I got into this sport. 

I dove head first into this with Big Bore Airguns and the AirForce Texan .35 cal when it came out a few years ago and was my first big step into PCPs. Everyone on the forums complained about "horrible harmonics" which went counter to what I had been taught. There is no such thing as BAD harmonics, but just harmonics that haven't been controlled yet. I just knew there had to be a way to tame and control (tune) those wild harmonics being generated from a beast of a big bore airgun. So I created a shroud with rubber damping parts at both ends with a collar weight on the barrel to slide up and down to try and find a harmonic accuracy node. That device (which interestingly ended up looking like the SS shroud they came out with a few years later) really did help with the harmonics, but the sliding collar weight was a total crap shoot to find a spot that allowed me to control group size. I knew there needed to be something more adjustable and repeatable. 

When the Browning BOSS system let their patent expire, there have been dozens of companies who have adopted a rotating weight at the muzzle approach to tuning. This is no different except for some specific things we have baked into this integrated shroud based on specific testing with the FX platform and barrel system. The other big goal in the design I worked with FX to develop was to NOT make it look like you went down the isle of Home Depot and grabbed a bunch of plumbing parts to throw on your barrel. My design was both focused on form and function. But in oder to get the barrel tuner to have the mass it needed to make changes during rotation, we tested a few different alloys and found one that worked amazingly well. There is also quite a bit of damping technology we have baked into this accessory that minimizes the smaller vibrations and longitudinal vibrations to make the harmonic frequency "cleaner". Here is another video I posted to day with some deeper conversations on this topic:

https://youtu.be/5e30KOsuylk
 
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