That won't work at all. If was cold outside when they tried to shoot it it would have seized up like a hot bearing. If to much is in there it can also create a suction and keep the gun from cycling at all.The weights made the noise for the OP, but the first time I shot an AR and heard the "twaaang!" I said "No way."
I did some research, and found that you can lightly coat the buffer spring with grease to kill the twang. I gave it a light coating of synthetic moly wheel bearing grease, and it worked (and works) great. Less noise, smoother action.
Recommended it to a friend; she packed her receiver extension tube with grease. That didn't work so well.
Her rifle worked fine again after we dug out all the extra grease.
