I'd like to build a can that will work for a 9mm AR pistol/SBR AND for a 9mm Pistol (PPQ Navy).  What is a good set up for this?  Am I right understanding that I will probably want a booster/Nielson device for the handgun, but will not want it for AR?  Struggling to understand what's available out there.

Honestly, I think 2 purpose built cans is the better option. But what you want is doable. Using the Gemtech or Liberty LID/Booster for the pistol and swapping to either a 3 lug or fixed barrel mount for the rifle. You can also remove the piston spring in the booster and replace with a solid spacer when using on rifles. 1/2x28 direct thread on both hosts. DM and SDTA sell tubes and adapters for the boosters, just figure out baffles and spacing and build.

I built a heavy duty Ti 35cal can for the rifles, up to and including .358winchester. Just so happens to work great on 9mm SBR, 357max Handi rifle and any other sub 35caliber host.

Can't I only have one threaded end cap per tube?  Is there an endcap that will work with both a booster and a direct thread adapter?  Pistol is threaded for 1/2-28, AR is threaded for 1/2-36.

So don't quote me but, pretty sure mounts and boosters don't qualify.  The booster adapt sold by them is just like a threaded end cap on any other can, it's accepts a different thread pattern, that just so happens to be made by liberty and Gemtech. Really no different than all of us who use Griffin Armament mounts.

The B tube sold by SDTA is a direct thread, no endcap to the Gemtech and Liberty. I built a dedicated 9mm on it, also wouldn't recommend it over the other options as it is heavy, thick, and smaller volume than the other options. I turned my b tube down to save weight and went long to get volume. For a do it both can, the DM 1.375" tube and ends is the ticket.

The 1.375 tube that DM makes is probably the best choice for what you are looking to do. Gemtech and liberty make boosters and 3 lug adaptors that can be used. The B tube adaptors from SDTA are also the same thread pitch and make good direct thread adaptors. I have the gemtech 3 lug and booster and they are aluminum. I'm pretty sure the Liberty stuff is stainless, if that makes any difference to you.

Diversified has the Titanium 1.375 in stock in 6.75 and 7.75 lengths.

The easiest thing would be to buy a booster and use a solid spacer in place of the spring when shooting the AR; this more or less converts it to a direct thread mount.  Because the barrels are threaded differently you will either need two pistons, or just buy one piston and convert the AR barrel to 1/2-28 by rethreading, using an adaptor or replacing the barrel altogether.  If you plan to use a 3-lug mount on the AR then just order the mount in 1/2-36 and buy whatever adaptor you want.  If you go with the DM 1.375 tube, order the kit with end cap of your choice and the booster bushing.  The Liberty and Gemtech boosters and 3-lug adaptors will screw right into the DM booster bushing so are easy to swap.  There is a lot of interpretation of NFA rules but many contend that mounts are not suppressor parts.  In this case the booster bushing and end cap hold the internals in place so a booster or 3-lug adaptor are just different mounting options.  

Thanks for all the input guys.  I went with a 1.375 tube from DM and the booster bushing.  I am going to order a Gemtech LID when they're back in stock and have a direct thread adapter that is compatible with the DM bushing for the AR.  I'll post pics when I get it all in case anyone else needs easy reference for a 9mm set up.

Legally speaking, you cannot change anything on an F1 can. At all.

If you decide you want a booster to work with tilting barrel pistols, then you cannot swap out for a trilug when you want to shoot it on an AR. Same for the other way around.

Gemtech, SilencerCo, etc can get away with it because they are MANUFACTURERS vs you as a MAKER. Manufacturers get variances from ATF, makers cannot. At least, none have ever been approved, ever. An F1 can is a one shot deal, once it's done, it's done. Having extra parts lying around for your F1 can are considered silencer parts and require stamp, registration, etc.

Two purpose built cans are what you seek. Better that way anyway, Make the AR one shorter and fatter with a 6" D cell trilug (mine is every bit as quiet as an Octane 45HD on my MP5) and a B tube for the boostered pistol one.

I think you're missing how it'll work. Each device would be part of the host, not the can.

I guess the trilug QD mount and piston / nielsen device will be welded to the host then.

Nope, neither are any other muzzle devices unless pinned to make length....

You almost have it right, but if the form 1 can is made to accept adapters it is ok to use those adapters as they are sold as non silencer parts.

So if you make a can that has an endcap threaded to the adapter thread, the adapter is not a silencer part.

Similar to having a silencer threaded to 5/8x24 and using a thread adapter to attach it to a barrel that has 1/2x28 threads.

FWIW, the manufacturers don't "get away with it" because of a variance. They do so by using the system available to them through tech branch that allows them to supply a prototype to determine whether or not it is considered a "silencer" by ATF.

In the cases like the Gemtech Multimount - ATF tech has determined what is the silencer and has allowed the "adapters" to be just that and not silencer parts.

Form 1 "makers" don't have access to this system as they are not able to legally produce a prototype to submit to tech branch.

As others have noted the booster and direct mount are legally just adapters and not silencer parts.  My (basic) understanding is when you Form 1 a can, you may have a tube, two endcaps, and whatever baffle set up.  In this case, I will have an endcap that is 1 3/16-24.  I will then make use of one adapter for the AR and a different adapter(booster) for the PPQ.

Also, you're the second person to tell me "just build two cans."  It's nice of you to be so cavalier with my pocket book.  I don't want to spend the extra money on a separate stamp and can.  I knew there was a way to make the set up I wanted I just wanted some guidance.

Those adapters are sold by gemtech (for example) for use on their multimount and that's what they are sold for.  You buy it and use it on a platform not intended for then it becomes a silencer part.

It's inside your F1 can, its part of your F1 can, and CAN NOT be swapped. As stated before, makers do not have access to the submittal system that manufacturers have to determine what IS and IS NOT a silencer part. ATF has blanket statemented ALL F1 silencer components are silencer parts. Feel free to write technical branch. Or bend the words however you see fit to get the results you want, see what ATF thinks of that.

With that argument, everything could be considered a silencer part. If I design a can to mount to A2 flash hiders, then all A2 flash hiders become silencer parts. Same with Griffin mounts and the plethora of other muzzle devices. If I thread my hunting rifle for 1/2x28 does that make the barrel a supressor part?

Call it a grey area if you want.

The ATF tried to pull this crap with YHM, back in '09. It didn't fly then and it doesn't apply today. Show me otherwise.


I'm not sure where you're getting your information, but it's incorrect. Yes, Mfr's can apply for an official determination on a part. However, the decision applies to the part and not a single use. Unless the end user were to modify it (from its original design), the Gemtech LID is NOT a silencer part, regardless of who uses it.

Yes, the SiCo endcaps can be put on a blast shield, as the Mfr has proven (and ATF confirmed) the existence of a dual use. No, I can't do the same w/ my homemade parts. This is not the same as me swapping a LID from one can to another. Or any other mount declared not to be a silencer part.

Please, please, please, show me this blanket statement from the ATF. There is not a single open letter or official ruling that covers this. Anything else would hold the same weight as an opinion letter, zilch.

Use a little common sense here.  Anything you can buy on Gemtech's site without providing a tax stamp....   Is not a suppressor.

I've had this discussion before and have researched it myself. Here's what I found.

Per the NFA handbook:
“2.1.7 Silencer. A firearm silencer...includes any combination of parts, designed or redesigned, and intended for use in assembling...a firearm silencer.”

Modular silencers are commercially available, ie. they contain multiple end caps to fit different threads & calibers. This is legal because they have a unique design that allows the end caps to not be a “silencer part.” With monocore designs, the baffle stack is usually a single piece that includes the end cap that screws into the muzzle end. The barrel end cap is not needed to keep the baffles in place. Thus, it is not integral to the assembly of the silencer. The extra end caps in this scenario are treated as barrel adapters and are not regulated as silencer parts.

With Form 1 builds, people use freeze plugs, battery storage cups, or other things for baffles that do not retain themselves in the silencer tube without BOTH end caps. In this scenario, the threaded end cap is necessary for the assembly of the silencer and it IS treated as a silencer part. If you have a LID for the pistol, AND a tri-lug adapter for your SBR, and these are necessary to keep your baffles in place, then you have what the BATFE has defined as a “spare silencer part.”  Now, whether it's easily discoverable that you have a lid at home while you're on the range with your tri-lug adapter is a point some folks bring up to argue that these types of determinations are "arbitrary and capricious." I can't say I'd disagree, but it's still illegal non-the-less.

There are ways you could make a Form 1 silencer that wouldn’t need the 2nd end cap, such as welding the front baffle or something. Form 1’s can be modular, it just has to be done very particularly. It really isn’t a grey area, it’s just misunderstood because the ATF doesn't make this information easily available or interpretable.

I hope this helps clarify things.

Geez, I'm not sure where to begin. Your quote on the definition of a silencer is about the only thing you got right.
I never found out who started the rumor about holding in baffles, but this has nothing to do with whether an end cap is a silencer part or not.
If you use a snap ring (or other device) to hold your baffles, so as not to rely on the end cap, all you've done is made another silencer part. Your end cap is still a silencer part as well.
The real reason the SiCo (and several other) end caps are able to be purchase OTC and swapped out is due to time and money being spent on behalf of the Mfr to make it so. They've proven to the ATF that these parts are not designed, intended, or made solely for the use as a silencer part. They sell muzzle brake, flash cans which also use these end caps. A Form1 builder does not have a manufacturing license and, therefore, is unable to go about this same process.

As for LIDS/Nielsen devices:
Retails purchasable boosters are not silencer parts, because their Mfr's have, again, spent time and money to have the ATF deem them as such. They provide no sound reduction or enhancement of the silencer. They simply allow the firearm to function properly. Without the booster, the silencer will still muffle a shot just as it did w/ it on. You can research the BS YHM went through in '09, I believe I referenced this in an above post, and get more info there. Not to mention the fact that they are sold at retail, on a daily basis.

You would not be able to, legally, remove the booster from an Octane and continue using the same silencer w/o having an illegal spare, silencer part in your possession. This is because of the Octane's design. It adds volume to and serves as an initial chamber for the silencer.

As for adapters:
If it is a simple thread adapter (ie: going from 5/8-24 to 1/2-28) than it is not a silencer part. It is not a part designed to be used for the muffling of a gunshot. It does not enhance nor provide any properties to which a silencer would benefit. It merely facilitate the mounting to a firearm by which the silencer may be used. If it is an end cap (specifically the rear) than it is indeed a silencer part. Not because it holds in the baffles, but because it holds in the gas and muzzle report. If you remove your rear end cap, to facilitate mounting a LID/Booster, you can be found in violation of NFA law. Once you've mounted the LID, your silencer no longer needs the end cap to properly function, as designed, and you are in possession of an illegal spare part.


Please, stop spreading misinformation. There is plenty to be had and it helps none of us.

I don't understand the need for the snarky and self-righteous response. However, I won't dispute the possibility that I'm misinterpreting NFA laws and ATF determinations - It's really not that hard to do.

My issue is that you don't provide any references or sources for your own positions. Forgive me for being skeptical on the internet, but that doesn't give them any greater weight than my own position, even though I do base mine on ATF publications.

I''m happy to recant my position and embrace your understanding if you can provide sources and/or references that substantiate it. Otherwise this is simply two opinions that don't help the OP.