Long story, short answer.....here goes.....
As many of you know, when M-bars are installed, you get a bit more bar vibration. I common solution is to put lead shot (or bar-snakes) in your bars. Unfortunately for some of us, lead shot is not all that easy to come buy.
You see, while I was born on the south side of Chicago, I grew up in Iowa. So I'm used to walking into a Wal-Mart with a drivers license and walking out with a shotgun. Did I mention I also lived in Texas (Dallas and Garland)? Yeah....not hard to get shells there either.
Well, in Illinois, things are run a bit differently. First, no one sales lead shot by the pound. The closest case I found was a 25 pound bag of lead shot for $25.....that was not going to work.....being that I only needed an ounce at the most. Second, you have to have a FOID card to even handle ammo here. I had thought about buying a whole box of shells just to cut open one shell for the lead...but I could not even do that. Bummer. I bought a pistol years ago in Iowa, and the process was pretty easy. In Illinois, I felt like I was trying to get another passport to get a FOID card....I really didn't feel like going through all of that hassle and expense just to get an ounce of lead shot. Plus, I've heard mixed reviews on liquid bar-snake, and I didn't want to waste 50 bucks on a chance that it would not work.
OK, with that said, here is a half-dollar, easily reversible, so simple it's stupid, remedy to bar vibrations.
Washers on the inside of the bar end caps. It's like "duh"...
At Home Depot, the regular 1/4 inch cut/flat washers are six cents each. They fit inside the M-Bars almost perfectly. Eight of these washers (4 for each side), and some tiny bits of rubber (I used an old inter-tube I got at a bike shop for free), will give you a decent amount of extra weight at the end of the bars. Install time is all of 4 minutes.
To easily get a hole in the rubber, use a hole puncher. (or you could just buy a couple of rubber washers also)
This quick fix has helped reduce my vibrations big time. Heck, I might even be able to squeeze 5 washers on each side....it's only twelve more cents to find out.
Here is the bar-end screw (without the bar end obviously) with the washers and my rubber "resistance" to keep the washers from vibrating. You can probably place a piece of rubber between the first washer and the bar-end cap itself to help reduce vibrations even more. When you use and old inter-tube, you can cut the rubber to fit the inside diameter of the bars perfectly.
Just my "fifty" cents....
:-D