Harmonic Dampener question

**wboggs** · April 15th, 2008, 08:39 PM

Can someone tell me just what a harmonic dampener does and how it works? I know it has to do with accuracy but after seeing a cutaway view of one, I am clueless as to how it works.

**rwilson452** · April 15th, 2008, 10:43 PM

Being a little over simplistic, when you fire a gun the barrel vibrates. a dampener reduces the vibration. if the barrel vibrates less it will be more accurate.

Originally Posted by wboggs

Can someone tell me just what a harmonic dampener does and how it works? I know it has to do with accuracy but after seeing a cutaway view of one, I am clueless as to how it works.

**Tomcat088** · April 15th, 2008, 10:49 PM

rwilson gave a pretty simple and accurate explanation. You will hear people refer to "barrel harmonics" and it just has to deal with how the barrel vibrates as the bullet travels down and the moment it exits the barrel. Something that is related that you will hear reloaders talk about is, "tuning the load to the next node". Vibrations move in sine waves, up and down. You will never completely stop the vibrations of the barrel, so what you want to do is make it so that the end of the barrel is on a "node". If you remember physics, a node is the still area (almost still) right where a sine wave begins or ends. When you tune the load, or adjust the vibrations of the barrel (by weight distribution etc), you help make sure that the very end of the barrel (the last part that touches the bullet) is completely still. So you can't make the entire barrel be still, but you can make it so that the very end of the barrel is still. I hope that makes sense.

Edit:
Here's a link that might help you picture it http://www.acoustics.salford.ac.uk/f...ves/string.htm

Look at the 3 and 4 animations FROM THE BOTTOM. Do you see how there is a node area where there is no wave. That is what you want the end of the barrel to be at, a node, so that it isn't jumping up and down. This is the purpose of a harmonic dampener or people "tuning loads to nodes". Hope this helps the visually learners picture the concept.

**Warners Surplus** · April 15th, 2008, 10:52 PM

Originally Posted by wboggs

Can someone tell me just what a harmonic dampener does and how it works? I know it has to do with accuracy but after seeing a cutaway view of one, I am clueless as to how it works.

There are so many different Harmonic Dampeners on the market. Without knowing which one you mean it is hard to explain how it works but I can tell you.

Barrel harmonics play a major part in precision accuracy. Even tho it is unseen to the human eye. A barrel actualy vibrates when a bullet passes thru it. Do to MANY different factors the Harmonics may change over the length of the barrel. High Barrel harmonics causes the bullet to vibrate with the barrel and if the vibration,harmonics is bad enough then the bullet can leave the barrel with a slight wobble which plays hell on accuracy.

Precision rifles tend to use a Heavy and Straight contoured barrel which cuts way down on harmonics because of the thickness of the barrel and the straight contour helps keep harmonics consistent over the length of the barrel.

Std. hunting contour barrels tend to vibrate more because of the light contour and tapered contour. If you could actually watch a std barrel vibrate you would also see varying degrees of vibration caused by several different reasons including metalergy. You could have a denser area that has higher carbon or iron content and will vibrate less and you could have areas of high coke content that vibrate more. That is all on a microscopic level ofcourse from the original mixing done at the foundry and the inabilty to get an EXACT mix.

Alot of the dampeners that are on the market are small and designed to be moved up and down the barrel to find the ideal location that it works best in dampening the barrel harmonics. That style dampener calms a wild and high harmonic vibration area in the barrel. Some of the do it by adding weight and some of them are made from rubber and help but dont do a whole lot. I have seen some guys shoot better after installing the rubber ones but in my opinion it is more of a placebo effect than anything.

another thing that causes a big variation in barrel harmonics is if the barrel is free floated in the barrel channel or not. A barrel that is not free floated tends to vibrate slightly from the chamber to the end of the stock where it is contacting the barrel and then starts to vibrate again within 1 or 2 inches ahead of the contact area. This big variation in barrel harmonics has adverse affects on the bullet stabalizing and ofcourse hurts accuracy.

I hope that helps.

LOL as usual I type WAY too slow!! There were ZERO replies when I started typing! LOL

Rich W.

**Tomcat088** · April 15th, 2008, 10:59 PM

lol, that's alright Warner, that's a very nice reply. I covered it from a slightly different area than you, and I think overall between the 3 of us we seem to have it pegged down pretty well.

**justashooter** · April 16th, 2008, 12:25 AM

this concept dates back to the 20's. the application that sees greatest advantage is large caliber artillery, due to the extreme effecive range and the expressed energy in scale. modern tanks and artillery guns have been dampened since WW2.

**BenningBoy** · April 16th, 2008, 01:01 AM

I believe this applies to bayonets on old surplus rifles as well. Something about actually fixing the bayonet to the rifle greatly effected accuracy. So in case of an assault weapons ban, it's not a bayonet lug, it's a harmonic dampener mount.

**netw0rkpenguin** · April 16th, 2008, 02:49 AM

Originally Posted by BenningBoy

I believe this applies to bayonets on old surplus rifles as well. Something about actually fixing the bayonet to the rifle greatly effected accuracy. So in case of an assault weapons ban, it's not a bayonet lug, it's a harmonic dampener mount.

Yes, the M44 mosin nagant needs the freaking bayonet deployed to shoot within 1 minute of peasant. If its folded you're shooting way left and low. You get great looks at indoor ranges deploying a bayonet and shooting a fireball out of a mosin :-)

The 91/30 the point of impact seems to be the same with and without the bayonet.

**wboggs** · April 16th, 2008, 07:18 AM

Excellent, excellent replies; thank you all!!

SO, hence the name HARMONIC Dampener. Whoda guessed harmony would relate to a gun? That's what confused me about the name.

Funny just yesterday I went to Sportsman's Warehouse to lust over 223's and was handed a Ruger M77 that weighed a ton. Now I understand completely why that barrel is so heavy.

I'm also a 35+ year, anal as hell re-loader and for the first time know about and understand this facet of how reloading is such a valuable tool to accuracy. (Incidentally I just nailed my Kimber, Gold Match load to a 1 1/8 inch 5 shot group at 50'. You cant even identify 5 shots as 1 went through an open hole)

Thank you, thank you all. EXCELENT!!

**BenningBoy** · April 16th, 2008, 12:17 PM

As an aside, this all presented itself to me watching a tactical shoot on TV. At one station, a guy had to shoot through a hole cut in a steel plate. He fired one round with no problem, but on the second rested the barrel against the steel as support, and was WAY off. Though supported, the plate interupted the harmonics. Weird, but also makes sense.