Overall length & SBR check
A suppressor makes a firearm longer, which is the safe direction. Pinning and welding one makes it count toward barrel length, which is how a 14.5-inch upper becomes legal. This draws where you land against the 16-inch and 26-inch federal thresholds.
Your configuration
Barrel length is measured from the closed bolt or breech face to the muzzle, with the action closed — not from the front of the receiver. Overall length is measured with any folding or collapsing stock in its extended position.
Where you land
Important limits on this tool
This is arithmetic against two federal numbers. It is not legal advice, and we are not lawyers. The federal minimums are 16 inches of barrel for a rifle, 18 for a shotgun, and 26 inches overall for either. Falling below them makes a firearm an NFA item requiring its own separate registration and approval before assembly.
The $0 transfer tax that took effect on 1 January 2026 covers SBRs and SBSs as well as suppressors. The registration requirement did not go anywhere — only the tax did.
What this does not account for
- State law, which is frequently stricter and sometimes prohibits these configurations entirely.
- Pistols and braces, which are a separate and unsettled area. A length calculator is the wrong tool for that question.
- Assembly order. Possessing the parts to build an unregistered short-barreled rifle can itself be a problem, depending on circumstances.
- Measurement disputes. Tenths of an inch matter and methods vary.
If you are within half an inch of any threshold, confirm with your dealer before you assemble anything. This is a category where being approximately right is not good enough.