odd "ping" sound when bolt closes in AR-15

[cardiackid]

I just finished transitioning my AR-15 from a hobby shooter to one optimized for 3-gun and have noticed an odd sound when I charge the weapon (unloaded). All parts have been assembled as directed, torqued, etc. to the various manufacturers recommendations. Here is what the two builds are comprised of from muzzle to buffer tube for reference on where this new sound may be coming from:

Previously:

14.5" Sabre Defence barrel (blued, chrome lined)

Phantom Flash Hider

Daniel Defense Aluminum low-profile gas block

Daniel Defense 10" Lite Rail

Colt Auto-style Bolt and Carrier Group

Carbine "H" Buffer

Standard Carbine Buffer Spring

Mil Carbine Buffer Tube

Now:

18" Stainless RLGS Bravo Company

JP Tactical Comp (stainless)

JP Adjustable .750 Gas Block

JP Extra Length (15") Hand Guard

Young NM Light Bolt/BCG

JP Low-Mass Buffer

Standard Rifle Buffer Spring (waiting for Tubbs CS flatwire to arrive)

Rifle Length buffer tube

I have never noticed this metallic "ping" noise with other weapons when the bolt goes into battery - just wondering what this could be caused by and if anyone else has experienced anything like this. My ear is more tuned to our work guns (M4s with usually thousands of rounds put through them, thus the metal parts have worn against each other) and they have a distinctly different sound when the bolt goes into battery with an unloaded chamber. The only thing I can compare this new sound to is that of an aluminum baseball bat hitting a ball.

My only WAGs are:

The different metal qualities in new parts (stainless steel now vs. the previous)

The possibility of the Young MFG bolt being machined slightly oversized for tighter tolerances (simply a guess based on "stuff I've read on the internet" which I tend to take with a grain of salt 50% of the time)

The lower mass of the lightened bolt carrier and buffer vs. the heavier Colt FA-style bolt/carrier and carbine H buffer

The bolt possibly hitting the face/throat of barrel when it goes into battery (IE, new weapon - new parts, new sound).

Any input would be appreciated.

[Graham Smith]

Does it make the same sound with the muzzle pointed up as with the muzzle strait or down? Possibly from the weight inside the buffer shifting?

[cardiackid]

No - the sound did not change regardless of where I pointed the muzzle.

- However -

Your suggestion did let me dial in on it as I repositioned the weapon and listened for it each way. As a right handed shooter, I had my right hand on the grip and my left hand on the charging handle. When I charged it with my right hand and used my left to grab the handguard, I noticed the sound was distinctly muffled and different. It has something to do with the sound of the bolt going into battery being amplified by the way the JP hanguard mounts to the barrel and receiver. I found that if I charged the weapon and let the "ping" ring loudly, I could instantly dampen it by putting my hand around the JP handguard. Thanks for your help - looks like the source is identified and not anything wrong with the weapon assembly.

[lynn jones]

shoot it with out ear plugs, you won't notice it any more. just kidding

[Powder Finger]

Carrier key hitting and moving the gas tube?

Edited February 16, 2011 by Powder Finger

[carharttfarmer]

Carrier key hitting and moving the gas tube?

thats my quess to i just put together an 18inch upper to and the gas key hitting the gastube was making it ping and rattle aginst the hand guard a slight bend and the noise went away

if you take the handguard off you can watch as the bolt closes and see if thats the problem

[Bryan 45]

It's probably the handguard. I have a couple aluminum tube handguards that make a similar noise. Kind of like a tuning fork, right?

It's never bothered me, I don't hear it when the rifle goes off.

[Alpha]

With new barrels and new bcg's, there can be head space issues. I've never heard of a head space issues causing a ping though. You might check the gas tube and gas key. There are many AR nuts on the forum that can tell you exactly where to look. If nothing works, take it to a local gunsmith.

[cardiackid]

It's definitely the handguard. Just like Bryan45 said - the ping sounds exactly like a tuning fork and it's muted out entirely as soon as I grab the handguard. I double checked the gas tube as well and it's good to go. Thanks everyone.

[want2race]

You can use cut rubber inner tube and wrap somewhere around the tube. Acts to dampen the tuning fork. Or, just keep your off hand on the tube.

I have a long browning type flash hider on my FAL and I use a high temp O-ring on the end to reduce the PING I get with every shot.

[DocMcG]

JP Low Mass Buffer and Handguard combination makes that cool "PING!" Great, Isn't It?