Installed Troy MRF FF Rail - Issues

[BuffCyclist]

I recently bought Opie011's Troy MRF 10" free float rail and installed it yesterday on my M&P15OR(T). I installed this per several tutorials I found online (albeit VERY straight forward) and used a Magpul AFG across the top rail gap between the upper and MRF rail to get it to line up. I used blue loctite on all 5 rail screws and let them dry about 5 hours before finding my problem out. I installed a Troy low profile gas block, dimpled and red loctited it after ensuring the BCG would fully seat on the gas tube without interference. Additionally, I installed a Smith Enterprises Vortex flash eliminator and a BCM Gunfighter Mod4 (medium) charging handle.

Now, onto the problem. Whenever I pull back on the charging handle and let the bolt slam forward (like normal) I hear a high pitched noise resonating from the entire rifle. The rifle seems to have turned into a tuning fork, that resonates for 4-6 seconds before fading away. I'm inclined to think it has something to do with the rail, but am thinking it could be due to the BCM GF charging handle, since this is the first time I've used one.

I asked Opie011 about it, and he was not aware of any high pitched resonance, but admitted he never really paid attention to the noises his rifle makes when charging it.

Has anyone else ever experienced this? Am I the only one that listens closely enough to the noises his rifle makes to pick up on it? Is it the spring for the latch on the BCM GF CH?

I'll be taking it to the range either this weekend or next to make sure everything is working properly. If everything is working fine, I may just ignore the whine, or at least attempt to!

[SA Friday]

Sounds normal to me. I had the same effect when I floated my hbar. I bet the AR you modified wasn't floated before and that's why it sounds weird. Try this, hold the ar by the front handguard and then charge the bolt by letting it slingshot forward. Does the sound not happen? Then its harmonics from the floated handguard.

[BuffCyclist]

Hm, I guess now that I think about it, it does make sense that the FF handguard is acting as the tuning fork. I'll test it when I get home and see if it does it when I hold the handguard and then report back.

[Fromk]

It's the Vortex flash hider. Give it a little ping and you'll hear it loud and clear. They have a very distinctive sound.

[BuffCyclist]

It's the Vortex flash hider. Give it a little ping and you'll hear it loud and clear. They have a very distinctive sound.

Hm, well I heard they had a ping when shot but didn't think about THAT being the cause. I guess in theory it is just a 4-prong tuning fork. I'll try that when I get home. I can always remove it quickly too and see if the rifle makes the resonance without the vortex.

Thanks for the tip!

[opie011]

I hope you get it all figured out.

[BuffCyclist]

I hope you get it all figured out.

Thanks, I'm sure I'll get it figured out. It's nothing with the quality of the rails or the fit, just something new I observed and was wondering if it was common. But if this is normal with all Vortex FE's or free float handguards, then I'll just accept it and attempt to tune my guitar!

If nothing else, I'll just wear a second set of ear plugs while shooting!

[SA Friday]

Doubt you'll hear this when shooting. Different wavelength of sound, different type of energy transfer into the part causing the sound.

[BuffCyclist]

Ha, yea I know I won't hear it while shooting. I'm excited to take it to the range though, it's been a while since I've gone and I want to get my BUIS zeroed!

[BuffCyclist]

Well what do ya know?! It's the Vortex Flash Eliminator!

Just got home, pulled back on the charging handle, let her fly and heard that resonance. Immediately touched the Vortex and it dampened out VERY quickly! Glad it wasn't anything that it wasn't supposed to be doing.