I think you meant "as long as the range says you can use NFA items there."as long as the range says you can't use NFA items there.
Don't your forms have personal information on them? Unless its LE asking, I don't see any reason to afford someone like that an answer.
Surprise! An LEO doesn't even have the authority to request a Form 4. By ATF regs, you are only required to show your paperwork to an ATF agent.
If you were shooting at a public or private range and a stranger was firing a NFA item (SBR, Suppressed, SBS, Select Fire Weapon or AOW) would you ask him if he had his Form 4 with him? Would you inform the authorities? or Walk away?
Surprise! In the state of Florida, NFA items are illegal unless properly registered with ATF. Therefore a LEO may request to see proof of your documentation. You can show him at the range or ATF can show him at the station, while you and your NFA items are "detained".
790.221 Possession of short-barreled rifle, short-barreled shotgun, or machine gun; penalty.--
(1) It is unlawful for any person to own or to have in his or her care, custody, possession, or control any short-barreled rifle, short-barreled shotgun, or machine gun which is, or may readily be made, operable; but this section shall not apply to antique firearms.
(2) A person who violates this section commits a felony of the second degree, punishable as provided in s. 775.082, s. 775.083, or s. 775.084.
(3) Firearms in violation hereof which are lawfully owned and possessed under provisions of federal law are excepted.