u/ChileRelleno414

I need some suggestions/recommendations for either buying or improvising a decent barrel clamp.

I need to time a couple of muzzle devices, on an AR15 and an AR9 barrel, preferably while still in the upper receiver sans handguard. I don't want to simply use an upper receiver vise block/clamp and risk any damage to the uppers.

I know an upper receiver rod is the best option for the AR15, but...