I've seen some discussion lately about converting pre ban uppers to use on post ban lowers. In reference to the bayonet lug. Must it be ground off completely or just made non functional by grinding off the teeth that lock the bayonet in place? If a bayonet lug won't hold a bayonet is it still a bayonet lug or is it just a piece of steel that has no function?

Just grind off the sides, if it doesn't hold a bayonet, it's no longer a bayonet lug.

Remove the whole "stud", bayonet no longer has a place to "index".

I faced much the same decision not too long ago.
I am a civil attorney, so I checked the statutes and the regulations, as well as some courts cases dealing with illegal firearms in general.
I concluded there is no answer in the law and regs to that question, but given the crazy BS decisions the federal judges (aka liberal overmaster kings) just make up to bust gun owners, with no logic or justification, I cut the entire lug off.
Do you you want, but better to be safe than sorry.
A really good idea would be to check with a local federal level criminal defense attorney in your federal district. (there are not many people who who do mostly federal criminal defense for long term living).
It may cost a few hundred, but he may give you a much better answer for your area, since the federal 'circuits' can all invent a lot of their own caselaw.

There is no answer to this one.  You can pay any lawyer hundreds of $ more than the gun cost and still not have any better answer than your own question.  This isn't the kind of thing that's going to get you in trouble all by itself.  It would be a "pile on" charge.

Do what you think is best.  Me?  The one I've removed, I took it all off.  I prefer the way it looked.  It's off, not pretending to be there.

Either way, no big deal.  If some butthead cop is going to charge you with something, he'll make something up.  Just read oneshotonekill's tale of woe.

Grind it off.

I'm a civil attorney, but know how prosecutors can be. Picture yourself in court... the prosecutor takes a bayonet... slips it on the lug... is careful not to tip the rifle forward so that it doesn't fall off... and then, in an overly-animated way, runs the bayonet into a life-size dummy while making some grunting noice.

"Now ladies and gentlemen of the jury... you decide whether this evil black massive killing weapon has a bayonet lug... I submit that it certainly does!"

Guilty - ten years of being Bruno's bitch.

Just grind it off.

Rather than hire a lawyer to do legal research which provides no guarantee of correctness, contact the ATF's tehnicial services branch and ask for an opinion.  A ruling would be sufficient to negate any criminal prosecution and would be free to boot.

I oringinally just removed the ears/teeth on mine. I posted asking if this was OK. My post illicited no response, so I soon thereafter decided to just cut the rest off and not risk it.

There is no legal definition in 18 USC 44 Section 921 of a Bayonet Lug, Folding Stock, Flash Suppressor, etc...so there is no legal definition of what constitutes a bayonet lug. Some (NSFJoJo and McUzi if I remember correctly) first stated that removing the earsa was fine, but others suggested removing it all.

As there is no definition, what constitutes a lug may vary by case, judge, etc. While one may say that one with the ears removed is fine, one may also say it still accepts a bayonet and therefore is still a bayonet lug.

Without a legal defintion I really doubt there will be any final determination. So, I just say remove it for your own sake. I have heard of no charges for violations of 922(v) (1994 AW Ban)or 922(r) (1989 AW Import Ban) on their own, so you might be OK. Then again, the ATF might make an example of you.