Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.
A good mate just bought an hmr so I`m making him a silencer as a gift as he`s always sorting my electrical problems in my garage and never charges me.
Core mostly done and in the white. Just anodising it now so it will be black shortly. Still to do sort out the carbon tube and back cap . Its going to be reflex with a thin carbon tube covering the barrel to keep it clean. The core is just over 5" long and there will be 5" of reflex volume when its done.
Last edited by nutshot on Sat May 18, 2013 1:27 pm, edited 1 time in total.
I`ll try and take some readings on my decibel meter Historian . Decibel readings are hard to go by though as when Ive tried before back ground noise and even cars passing a few hundred yards away ruin the results. Best decibel meter I have found so far is my ears
The hole in the side SRM is a grub screw to keep the tube in place . Nothing will vent from it I can`t thread carbon so its the easiest way to secure the tube to the core. The tube is such a tight fit that I doubt it would move without it though.
I have a 1.125" x 7" can for my 17 hmr with cone baffles. The muzzle blast is nearly gone and the sonic boom of the 20 grain bullet is less than a 223 or 308.
Ranb
SilencerTalk was a place I could disccuss making registered silencers without being told I was a criminal. That is no longer true. http://www.silencertalk.com/forum/viewtopic.php?f=132&t=99273
Tried it today and pretty pleased . couldn`t do a decibel test as I didn`t have the time to travel to somewhere quiet an open but I did a video of a couple of shots Muzzle blast was well tamed but can`t do much about the supersonic bullet.
I`ll be trying it on his gun at some point this week and let you know if its works good or is just a fancy barrel weight 
Muzzle blast was well tamed but can`t do much about the supersonic bullet.
I don`t use it on here as most forums think its porn and remove it 