Hi,
As scotchegg and samb have mentioned in so many words
is that there are not any "issues" per say but yes there are some "restrictions" better known as licenses/permits.
You will have to have an exporter in USA complete (with all the supporting documents) a DSP-5(Permanent Exportation) application and submit to the DDTC for review and approval.
Some of the supporting documents the exporter will need will be:
Signed PO
Import Permit from UK and/or an official (On letterhead) statement from UK authorities that an import permit is not allowed.
DSP-83 which the exporter should complete for you and send to you for signature.
And just before the International experts get involved and say, advise, comment, etc about this vs that.....Stocks and chassis fall under Subsection H.
Category I—Firearms, Close Assault Weapons and Combat Shotguns
*(a) Nonautomatic and semi-automatic firearms to caliber .50 inclusive (12.7 mm).
*(b) Fully automatic firearms to .50 caliber inclusive (12.7 mm).
*(c) Firearms or other weapons (e.g. insurgency-counterinsurgency, close assault weapons systems) having a special military application regardless of caliber.
*(d) Combat shotguns. This includes any shotgun with a barrel length less than 18 inches.
*(e) Silencers, mufflers, sound and flash suppressors for the articles in (a) through (d) of this category and their specifically designed, modified or adapted components and parts.
(f) Riflescopes manufactured to military specifications (See category XII(c) for controls on night sighting devices.)
*(g) Barrels, cylinders, receivers (frames) or complete breech mechanisms for the articles in paragraphs (a) through (d) of this category.
(h) Components, parts, accessories and attachments for the articles in paragraphs (a) through (g) of this category.
Sincerely,
Theis