Recently I had the opportunity to make a bulk purchase of used gun parts. As I buy and sell parts for old rifles and shotguns, I put the deal on hold as there was a good bit of full auto stuff in it. Mostly trigger kits, bolts etc. No receivers or anything like that. I've read through the NFA and didn't see much pertaining to parts. If I missed it I apologize for the question. IS it legal to buy and sell parts from full auto guns or do you have to be an FFL? Thank you.

I think this is a good question.

I've got several NFA items (Cans and SBRs) but I really don't know the ins and outs on Full Auto.  I mean I have a decent idea, but I'd not consider myself educated on the subject.

Mostly because I've never had the money to get anything full auto, so I didn't put the time in too figure it all out.  
That and you can get truck loads of BS info from not only Know it alls, but the ATF as well...

Super, highly illegal. I will handle this issue. Please forward me the the sellers info.

For the most part, parts are ok unless there’s complete M2 Carbine fire control kits or DIAS’s you’re totally fine.

It is sort of al over the place.

It depdns on the acion design what parts might be different enough to allow full auto operation.

Years ago someone came up with the idea of an 'auto sear' for a number of action designs.
Since each action is different the parts are different.
And what parts must be present are different.

For the most part BATFE ruled that ANY auto-sear is an NFA item.

Transfers require the $200 tax and registration just like a complete machine gun.

Around that time they also realized how easy it is to modify many 'open bolt' designs to full auto.
They pretty much will not approve a new open bolt design.

So long as you don't have certain things (drop-in autosears which convert semi-auto firearms to MGs, M2 carbine 'seven parts' which convert an unmodified M1 to a MG, etc.) then it's no different than any other parts. I have tons and tons of FA parts left from parts kits built into legal, closed-bolt semi-auto firearms over the years, and I simply don't worry about it.

Of course, that's Federally. I think a few states regulate any FA parts, so that may be different for you.

F/A part is parts, as long as it is not a registerable part. M16 as above, or complete HK trigger packs for example can be sold no problem at the Federal Level. Be advised, said parts along with a gun they can go in, could be MG possession.

Complete Wrong.

No they did not, which is why they are for sale everywhere without an NFA form.

https://www.hkparts.net/shop/pc/Trigger-Pack-Sear-Catch-German-Surplus-88p18304.htm

https://www.hkparts.net/shop/pc/HK-Semi-Auto-3-Position-Navy-Trigger-Group-89p155.htm

https://www.gunbroker.com/item/785007360

https://www.armsunlimited.com/Colt-M16-M4-AR15-Auto-Sear-Assembly-p/sp61622.htm

https://www.ftfindustries.com/category/M16FA.html

https://www.brownells.com/rifle-parts/triggers-parts/sear-parts/sears/auto-sear-assembly-a2-prod22435.aspx

eta

Perhaps the source of your confusion is the ruling that AR15 DIAS is a NFA item. THis has nothing to do with all the other sears that are not NFA.

https://www.atf.gov/resource-center/docs/atf-ruling-81-4pdf/download

You are invited to play with them.

Keep in mind how expensive losing is.

Most of the parts were AK47. Full auto bolt carrier groups, triggers and lower parts kits. I don't own an AK47. Like I said most of the stuff I deal in is vintage rifle, shotgun and revolver stuff. The lower parts kits were my main concern.

All AK47 parts kits imported I know of or bought back in the day came with the full F/A parts. Most folks either tossed the ones they could not use or sold them to 07/02 for post samples.

You are fine with those parts in your possession.

FYI:  AK’s only have one receiver. Fire Control Group ((FCG) trigger, hammer, rate reducer, sear, etc.) is a better term than Lower Parts Kit, since there is no upper/lower receiver.