Author Topic: Form 1 suppressor build (Read 18343 times)

bkoenig · « **on:** July 04, 2012, 12:32:16 PM »

OK, here we go. For anyone who's not familiar with this process, it is legal to build your own suppressors. The legal requirements are identical to building a short barreled rifle (SBR) or short barreled shotgun (SBS). You fill out ATF Form 1 and pay a one time tax of $200 to Uncle Sam, and send it all off the the ATF. After a LONG wait (mine took 6 months) if everything is in order you will receive your form back with a tax stamp. Once you have the stamp in hand you can legally begin construction. Building any part of the suppressor, even a single baffle or threading a tube, before that time is illegal and will land you in the graybar hotel if you get caught. $200 is a pretty cheap price to avoid having a really friendly guy named Bubba as your room mate. Don't be stupid.

I will be building a .22LR suppressor. It will be built out of 6061 Aluminum, except for the first baffle and the barrel threads which will be 303 Stainless for durability. Aluminum is fine for a rimfire suppressor, but is not strong enough for centerfire. The baffles will be what is known as a "K" baffle, because when they are viewed from the side they look like two K's back to back. This baffle type generally works well for subsonic and low pressure loads, but it is a little more complicated to machine.

Quick disclaimer: I am not a professional machinist. In fact, I'm not even a particularly good hobby machinist. I will most likely make mistakes in this build. Build a suppressor can be dangerous, both from running machine tools and from using the suppressor itself if it's not properly constructed. Don't attempt this without a full knowledge of the risks involved. I'm not responsible for your safety.

With that out of the way, let's start turning metal. I turned down a bar of aluminum to 1.027", which makes for a slip fit inside the tube. I don't want it too tight, as rimfire ammo is very dirty and this will need to be disassembled frequently to clean it out. The bar has been drilled with a .25" drill bit. I may make the final bore slightly bigger, depending on how my tolerances stack up.

6061 machines beautifully. A sharp bit finishes it to a mirror finish. Also, the chips are extremely sharp. I have a sore index finger to prove it.

bkoenig · « **Reply #1 on:** July 04, 2012, 12:35:27 PM »

Next steps - cutting the front "disk" of the baffle. Since I already had the bar chucked up between centers I just left it there for the first one. This was a mistake since I had to then part it off and rechuck it to hollow out the inside of the cone. The next one I'll be smarter.

bkoenig · « **Reply #2 on:** July 04, 2012, 12:36:57 PM »

Cutting the outside of the cone. The compound is set at 30 degrees to create a 60 degree cone. I didn't get any pics while I was machining the inside, but this is where I was dumb and had to part it off and rechuck it.

bkoenig · « **Reply #3 on:** July 04, 2012, 12:42:20 PM »

And here's the (almost) finished baffle. I still need to plunge a 1/4" ball end mill into the face and from the back to create a "scoop" in the face and a vent in the back cone. This will vent gasses to the outside of the cone. It's a little hard to explain but will make sense when I have pics. 6 more baffles to go.

bk09 · « **Reply #4 on:** July 04, 2012, 11:47:18 PM »

How did you learn to make this before you undertook the project? Did you take apart other suppressors and look at them or did you find blueprints somewhere? If/when I get the tools this would be of interest to me.

bkoenig · « **Reply #5 on:** July 05, 2012, 07:28:44 AM »

I did a lot of reading and asking questions on the silencersmithing forum over at www.silencertalk.com. There are a lot of very experienced builders there, so if you're interested that would be the best place to start.

Wesley D · « **Reply #6 on:** July 07, 2012, 04:03:47 PM »

Looking good Brian; keep up the updates and pics!

bkoenig · « **Reply #7 on:** July 07, 2012, 04:57:49 PM »

Ok, all of the baffles are done except for drilling the vent holes. I had to order a 1/4" ball nose end mill for that. A 6 month wait and I didn't get around to ordering a $12 tool until now

The top baffle is the blast baffle, which is closest to the muzzle of the gun. It's stainless steel and is about 50% thicker all around to make it more durable. The face of each baffle has a groove machined into it for the cone of the next one to fit into. I'm not sure if that was really necessary but I figure it should help keep things straight inside the tube. Next up, threading the tube and machining end caps.

gsd · « **Reply #8 on:** July 08, 2012, 09:27:15 PM »

Looking good Brian!

RobertH · « **Reply #9 on:** July 09, 2012, 02:26:06 PM »

BK, will you get your suppressors done for the NFOA meeting coming up? is there anyway i could put a few rounds in them if you're going to the meeting?

bkoenig · « **Reply #10 on:** July 09, 2012, 04:16:28 PM »

Sure, I should have the .22 done in the next week or so. Is your Mosquito threaded 1/2-28?

RobertH · « **Reply #11 on:** July 09, 2012, 06:46:45 PM »

i have an adapter for it. otherwise, its some weird metric crap.

bkoenig · « **Reply #12 on:** July 09, 2012, 07:15:31 PM »

Sounds good, we'll give it a try.

Got the tube threaded for endcaps tonight. This was the part I was most nervous about, since I had to use a steady rest for the first time. And my steady rest is a home made job. It worked ok, though, so now it's on to the endcaps. My ball mill also showed up, so I can cut the scoops and ports into the baffles. The baffles also may need a slight skim off their outside diameter since they're fitting really tight in the tube right now. Once they're all crudded up there's no way they'll come out when they're this tight.

JimP · « **Reply #13 on:** July 09, 2012, 09:32:33 PM »

bk, have you seen these:

bkoenig · « **Reply #14 on:** July 09, 2012, 10:13:30 PM »

I've seen them and honestly I don't see the point. If I'm going to wait 6 months and pay $200 for a stamp I'm going to do it right. Also, the ATF considers replacing a baffle to be the same as building a new suppressor, which will land you in the pokey. It seems to me that screwing a new filter on would constitute a baffle replacement in the ATF's eyes. NFA regulations are completely arbitrary and subject to the whims of the government so I couldn't say for sure, but that thing seems legally dubious.

bkoenig · « **Reply #15 on:** July 12, 2012, 10:50:34 PM »

More progress over the last couple of days. Got the tube threaded and both endcaps threaded to match. The mounting threads are also done. The end caps still need profiled to match the outside diameter of the tube, and the aluminum one still needs shortened. I still need to do the vent holes in the baffles and do some final fitting on them, make a spacer to hold everything in place inside the tube, engrave it, and apply some sort of finish. I'm kind of tempted to go with a brushed metal finish, maybe by spinning it in the lathe while holding some emory cloth up against it. It's finally looking like a real can:

And yes, I did run around the house tonight with it making "Pew! Pew! Pew!" sounds.

Wesley D · « **Reply #16 on:** July 12, 2012, 11:06:59 PM »

Quote from: bkoenig on July 12, 2012, 10:50:34 PM

And yes, I did run around the house tonight with it making "Pew! Pew! Pew!" sounds.

Yes, but did you hum the 007 theme???

Seriously though, the can's looking pretty. I'm looking forward to a range report once you get the final punch list finished!

jonm · « **Reply #17 on:** July 12, 2012, 11:20:54 PM »

Looks reallly good so far..

Might i suggest getting a longer handguard and tucking the suppressor.

bkoenig · « **Reply #18 on:** July 12, 2012, 11:29:39 PM »

I think I'm going to go the other way - shorten the barrel to 4.5" to keep bulk ammo subsonic. That should put the back end of the can right up next to the front of the rail. I can't decide if I want to do that myself or send it off to Adco. They'll do it for $65.

jonm · « **Reply #19 on:** July 13, 2012, 12:05:12 AM »

My gun is a 4.5" barrel with a 6" suppressor on it.

If you do plan to chop and re-thread, might Isuggest Long Range Precision. I had them do a barrel for me and it cost a whopping $20+shipping.