Quoted:
I don't think there are enough US parts to make an M1 compliant. There are some parts that
SRM Performance makes that can help get you there. Speed feed also makes a pistol grip stock. I don't think the proceeding parts are enough to get you to the magic number of 10 major US parts. Even if you did the ATF has never made a standardized agreement on what parts make up the 15 major parts in 922R. If you were to ask two ATF examiners you would most likely get two different answers.
WRONG. It is that you cannot have more than 10 imported parts. There is no such thing as "US part count" for compliance. It is only the number of (named) imported parts. Note that is is "more than" - i.e, 10 parts is okay, but 11 is bad.
Also, this is covered by 27 CFR 178, and not 18 USC 922. That is, the "parts count" thing is the expanded definition under the CFR that aids in fully describing that which is prohibited under the USC.
The twenty possible "named parts" under 27 CFR 178:
(1) Frames, receivers, etc
(2) Barrels
(3) Barrel extensions
(4) Mounting blocks (trunions)
(5) Muzzle attachments
(6) Bolts
(7) Bolt carriers
(8) Operating rods
(9) Gas pistons
(10) Trigger housings
(11) Triggers
(12) Hammers
(13) Sears
(14) Disconnectors
(15) Buttstocks
(16) Pistol grips
(17) Forearms, handguards
(18) Magazine bodies
(19) Followers
(20) Floorplates
A standard Benelli M1 or M2 will have - (1), (2), (6), (7), (10), (11), (12), (14), (15), (17), (18), and (20).
12 imported parts.
Slap on a US mag tube (18) and a US follower (19) and you may be good to go, depending on how the BATFE is feeling about stocks right then. They have issued letters that say that pistol-grip stocks where the grip and stock are one unit (like a Benelli) are only considered one countable part; but those letters of course only have any weight for their actual recipient, and do not carry any real force.
Now, if your M1 was imported before November 30, 1990, then it should be exempt, in my understanding.
And there's always the point that they have indeed allowed various Benellis in different "evil feature" configurations to be imported without issue - and 922(r) only applies to firearms that are otherwise disallowed from importation due to "non sporting" reasons.