https://www.luckygunner.com/lounge/short-barreled-rifles-vs-pistol-brace/
The “Secret Rules”
Unfortunately, the ATF has not been forthcoming about what other indicators they’re considering. We’re basically back to where we were before 2015. Again, individuals and companies are getting arbitrary and sometimes contradictory advice from various ATF personnel. Some sources have said that the ATF expects your brace-equipped pistol to have a length of pull under 13.5 inches. Some have said the ATF frowns on braced pistols with magnified optics unless it’s a forward-mounted long eye-relief optic. There are rumors that they don’t like braces on pistols weighing less than 40 ounces. So, something like a Glock with a brace attached to a stock adapter.”
The “Secret Rules”
Unfortunately, the ATF has not been forthcoming about what other indicators they’re considering. We’re basically back to where we were before 2015. Again, individuals and companies are getting arbitrary and sometimes contradictory advice from various ATF personnel. Some sources have said that the ATF expects your brace-equipped pistol to have a length of pull under 13.5 inches. Some have said the ATF frowns on braced pistols with magnified optics unless it’s a forward-mounted long eye-relief optic. There are rumors that they don’t like braces on pistols weighing less than 40 ounces. So, something like a Glock with a brace attached to a stock adapter.”
