I've had a Mech-Tech upper (G20 10mm) for 2 decades, and the barrel on mine is over 16". I never heard that there was a requirement to go the Federal tax stamp route with it.
This Mech-Tech topic has been debated for a long time, including a court case involving TC Contenders which are set up to accept rifle length barrel and stocks. The courts ruled That case was decided in 1992 in favor of TC.
This is from a site taking this from the Mech-Tech website in 2011.
"The CCU is not a firearm and will not fire without a pistol lower in place. The CCU is simply an accessory such as a scope or grips. For State and local laws you are advised to become aware of them relative to where you live.
As far as Mech-Tech is aware, the CCU in and of itself is legal in all States. We do know that in the case of California the combination of the CCU and a pistol lower becomes illegal under current law. If and when Mech-Tech becomes aware of any other special circumstances such as California, we will publish this information. Again, the customer has the responsibility to determine the legality of the combination in their circumstance. "
From Mech-Tech website now.
Is it legal to convert to CCU back to the original pistol?
Yes. The BATFE recently published a ruling which clarifies this – here is the link:
https://www.atf.gov/file/55526/download. There has been a lot of misinformation circulating to the effect that once the pistol lower has been assembled to a rifle configuration then converting back to the pistol constitutes ‘making a pistol from a rifle’ and thereby placing the pistol into the SBR (short barreled rifle) class. Not so. Please see our Forum for even further clarification. It is the first post on the Forum so you don’t have to spend time trying to find it.
Here's some excerpts from other sources.
First issue: an SBR is a rifle with a barrel less than 16" long - when using the pistol lower attached to the CCU you do not have an SBR. Secondly, the issue of converting back and forth is addressed by an attorney Stephen Halbrook in the link below:
http://www.stephenhalbrook.com/tc.html
Also is attached a PDF which contains copies of the Halbrook case and a letter from the ATF. Careful reading of both documents may answer your questions.
Before proceeding further, we are not legal experts and cannot officially give any legal advice - the ball is in your court.
Here is our opinion:
1) t
here is no ATF rule against restoring to the original pistol. (
I understand this not to be the case)
2) when installing a barrel equal to or longer than 16" to a pistol, the pistol can now be fitted with a shoulder stock without special licensing.
3) when #2 above has been assembled, you have a shoulder stocked pistol - not a rifle.
4) when switching barrels and stocks on a firearm frame, it matters how the frame began life from the factory - as a pistol or a rifle.
5) if the frame is registered as a pistol, it so remains.
Given the information provided by Stephen Halbrook it seems that everything is OK relative to the CCU. One fact in your favor is that the unaltered CCU cannot be used to assemble an SBR. The shoulder stock does not mount directly to the pistol frame.
I might point out that I am not an officer of Mech-Tech Systems corporation. I am an independent consultant hired on a contract basis for my engineering skills. I have been asked to address this issue because I also maintain the website.
If you are really concerned about switching back and forth, you might consider doing so in a non-public area.
Hope this helps,
Ray G. Herriott
BATFE Ruling
2011 BATFE Ruling
The bottom line is that if the serial numbered part of the firearm starts as a pistol it remains a pistol.
This also relates to the CAA MCK/RONI chassis where the pistol still remains a full pistol but contains within a chassis albeit within the pistol brace requirements, and ATF-defined use.
I have used the CAA MCK chassis and its' slick with Glock pistols.
CAA MCK
All this also pertains to the AR pistol world. When you get a lower as a pistol and build it as such (keeping it within ATF defined length parameters) you can convert the configuration into a rifle and the back to a pistol as long as you swap the appropriate major/key parts out, and go back to ATF defined length parameters.
My Mech-Tech upper (G20 10mm) is OK. It runs fine but is abit bulky in its current configuration. I haven't used it in years because of that, and since I went the CAA MCK chassis route with my G20.
My .02
