Class III firearms, NFA, AOW's, Destructive Devices

[CleverNickname]

Drilling a semi-auto AR lower now for a RDIAS is so illegal. Not familiar with the FNCs though.

I'm not talking about drilling a hole for a factory M16 style autosear. That's not kosher. I'm talking about milling the shelf on a lower so that an RDIAS will fit. Some makes of AR15s are forged at the factory with a low shelf and don't need to be milled, some have a high shelf and do need to be milled. Either way, milling a shelf doesn't affect the lower's ability to accept a factory M16 style autosear.

That's why the ATF lets S&H drill the autosear hole to convert semi-auto FNCs with a registered sear, because the S&H style autosear is in a slightly different location than the factory FN autosear.

The key is you can't modify a firearm so that it accepts factory full-auto parts, even if you don't actually install those parts in the gun.