>>64116390
>How effective
Slightly worse than a 22LR round out of a rifle at the muzzle. Its going to icepick hard for sure. But consider that icepicking is still a terrible afternoon at that distance.
>>64116404
Based, bring your p320

>>64112452
Shims are primarily to align ports on muzzle devices that have some sort of compensator built in. In some can/latch systems it also can be useful so your release mechanism doesnt get stuck behind your weapon light and be a pita to access.