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[Grainchaser]

Below previously posted on de-pinger material thread on April 20. I have since opened the air tube (after 100+ shots) to see if the pyramid depinger moved or anything else, and after inspection there was no movement or change to the material.

Also new to the Marauder, I got my M-25 in mid-February. After putting several hundred pellets down the tube I found the ping somewhat annoying and decided to proceed with a depinger. I read many posts on this and other threads regarding the theory, that the pinging noise is a result of harmonics/echo within the tube, and that one only needs to disrupt the sound waves to eliminate the ping. I also saw the posts regarding the potential for vinyl or other materials to break down in the air chamber environment, and decided that I would try a more inert substance, like silicone. (I do not have the ability to turn or shape a depinger out of a hard substance like delrin or teflon.
So, began my search for a suitable silicone tubing. After visiting local marinas, auto and hobby shops with no success, I went to Bed Bath and Beyond with one of those ubiquitous discount coupons that never expire, just to look and see.
And there it was, the the "Pyramid Pan Fat-Reducing Silicone Cooking Mat". List $14.99 for a 16.25" X 11.5" mat of little silicone pyramids. Reminded me of some acoustic tiles I had ever seen. I cut a section 8 x 2 pyramids (1.125 by 4.625 inches), cut open the apex of each pyramid, rolled it up to fit in the air chamber with the apexes facing in, and placed it about 6.5 inches down the tube after applying silicone grease. The fit was snug enough so it is not likely to move, but not at all difficult to insert.

http://s1344.photobucket.com/user/Grain ... b.jpg.html

I cut off the apex of each pyramid so that there would be no chance of the hollow pyramids sealing against the inside of the air tube when it was pressurized and thus causing them to flatten. The total volume of material being inserted into the air chamber was minimal.

http://i1344.photobucket.com/albums/p65 ... f605d5.jpg

http://i1344.photobucket.com/albums/p65 ... daf6a1.jpg

This next photo was taken when doing the after installation and use inspection. It appears that cutting the apexes was not necessary as there are gaps between the bases and the air tube wall.

http://s1344.photobucket.com/user/Grain ... sort=3&o=0

When tested after recharging, it appears to my naked ear that the ping was completely gone. I must note, however, that using the Performance Audio app on my iPhone there was no change in the decibel reading from before to after. Holding the phone in my left hand by the forward sling mount, I got consistent maximum readings of 101 to 103 dB both before and after inserting the depinger. Just no ping.
While the price for this depinger was relatively high, you can either create many depingers or actually use the remaining portion of the Pyramid cooking mat for its designed purpose, reduced fat cooking.
GC

[Sendler2112]

"Pyramid Pan Fat-Reducing Silicone Cooking Mat"

That looks too restricive. Did it change your tune?

[Grainchaser]

The tune did not change that I am aware of. However, I have not run a full string through the chronograph since the installation. Also, I am still using the factory tune rather than a higher power tune. Not sure if that would make any difference.
I will do a before and after comparison and post results when I get the chance. This material and location has proven to be very easy to remove, just grab with a hemostat and pull.
I did remove it (to inspect) and take a few shots, just to remind myself of what the ping sounds like, and then reinstalled it at 3.5 inches. New location seemed to work just as well as 6.5 inches to dampen ping. I am thinking that because it is a softer material, it will absorb sound wave and not reflect it.
GC

[DrS]

The tune did not change that I am aware of. However, I have not run a full string through the chronograph since the installation. Also, I am still using the factory tune rather than a higher power tune. Not sure if that would make any difference.
I will do a before and after comparison and post results when I get the chance. This material and location has proven to be very easy to remove, just grab with a hemostat and pull.
I did remove it (to inspect) and take a few shots, just to remind myself of what the ping sounds like, and then reinstalled it at 3.5 inches. New location seemed to work just as well as 6.5 inches to dampen ping. I am thinking that because it is a softer material, it will absorb sound wave and not reflect it.
GC

I tried your design after a visit to BBaB. It works like a charm, no ping. I inserted it at 5.5".
-Dale

[Wasatch]

the "Pyramid Pan Fat-Reducing Silicone Cooking Mat"

The pyramid mat worked great in my 177 where the ping was louder than the hammer (on my 25 the hammer/valve is louder than the ping so I can still hear tuning variations w/o depinging). Now i can hear the hammer and burping and changes while tuning.

The pyramid mat is also very easy to install and remove. The bent head of a bicycle spoke is a nice hook to push/pull the pyramid mat depinger in/out.

[jake37]

I installed 2 depingers as mentioned early in this post, here is a link to my video of My 25 Cal. Marauder with and without a depinger. look in the video description for the instructions and the size of the tubing i used, you can get the tubing at Lowe's. Video Link to YouTube... http://youtu.be/IxbxM7P-Vpo