Eliminate the ringing, modifing an open tine flash hider

**stahljaeger** · 01-08-16, 17:26

I got tired of my AAC 51t flash hider ringing like a tuning fork (as an engineer it also bothers me that it is lazy design work). So I took 10 minutes to "fix" it.

I drilled a blind hole down the middle of each tine of varying depths (enlarge 2nd picture for depths, they are not critical as long as they are sufficiently different). This makes each tine have a different stiffness and mass so they don't have the same natural frequency, and thus do not resonate. I used a carbide center drill to get them started close to center and chamfer the edge.

AAC_FH1.jpg AAC_FH2.jpg

Really, only 2 of the tines needed to be drilled, but I did all 3 so it looks better as my suppressor is usually on my sbr. Drilling a varying number blind oles in or grinding down some of the outside of the tines would have worked too, but likely look like a Bubba work.

I can still get it to ring a little if I try, but it isn't as loud and dies much quicker. However, the bolt closing no longer makes it ring, so functionally it should be gtg.

**Mars attacks...** · 01-08-16, 18:05

I use Smith Vortex flash hiders. If you hit them the right way there is a slight ring, but when firing I don't hear the ring. Ron Smith told me that was one of the reasons they abandoned the 3 prong configuration in favor of 4.

**SteveL** · 01-08-16, 20:35

I read a report a while back (don't recall which board) of someone drilling a small hole through the end of one of the prongs. They claimed it eliminated the ring.

**Clint** · 01-08-16, 22:37

Nice mod!

Sometimes the perfect symmetry of design causes unwanted side effects like vibration and harmonics.

A little de-tuning takes care of it.

For example, the guts of the newer monocore suppressors are purposely asymmetrical.

Another great example is the tread on truck tires, especially the knobby mud tires.

It used to be that each tread block around the tire was identical, but that caused a lot howling/droning at certain speeds.

Now they design each block to be slightly different. This spreads out the resonant frequencies and greatly quiets things down.

**stahljaeger** · 01-08-16, 23:16

A three prong shouldn't ring if the designer takes it into consideration. I don't see why four tines would be inherently better, but practically it should be a little better. I could be missing something though, I have never had any tuning fork like structures in anything I have designed and so have never gotten deep into those dynamics.

I did check the ringing after drilling one hole. It died out much more quickly than with nothing, but I was pretty sure if all of the tines were different it would be even better and it is. I suppose a bigger hole on one tine might have been good enough, but I didn't want to get the tines too thin, or accidentally change one of the surfaces that directs the gas.

I never thought about suppressor resonances affecting the noise or tone before but it makes sense. That gives me some ideas.

**K1tt3n5** · 01-08-16, 23:21

I'll have to try this out.

**556BlackRifle** · 01-09-16, 12:47

Originally Posted by Mars attacks...

I use Smith Vortex flash hiders. If you hit them the right way there is a slight ring, but when firing I don't hear the ring. Ron Smith told me that was one of the reasons they abandoned the 3 prong configuration in favor of 4.

Interesting. I have two or three rifles with the Smith Vortex attached. They ring. Not super loud / annoying but they do ring. How long ago did you pick up your Vortex? I wonder if there were some design changes between the time I got mine and when you got yours........