This is a gray area. Generally the "constructive possession" to create a machine gun rules wouldn't apply, since owning machine gun parts is illegal, but owning uppers with bayonet lugs is not illegal.
As long as you've got a legal way to assemble everything in your safe, I wouldn't sweat it, but that's just my personal opinion and tolerance for risk.
To be absolutely safe, you should leave them assembled (buy a bigger safe), and all in legal configuration, with no spare pre-ban parts, or even get rid of all your post-bans or pre-bans, but I think that'd be excessive.
locktite isn't enough to "cover" the threads, according to ATF - you have to use blind pin and weld, or high temp silver solder to permanently affix a legal muzzle brake to have it be post-ban legal.