I was given some .308 "small base" dies and some sized and primed brass. I have a new .308 bolt gun and understand the small bass dies are for semi-autos and lever actions.
I plan to get a Lee Collect die and a FL die for future reloading.

Is the "small base" sized brass safe to load and shoot once? I think it probably is safe but thought I'd ask.

Thanks
SH

Safe but not ideal.

Depending on your chamber it could over work the brass. You might contact RCBS and see what they can do. They could modify the small base FL to fit your chamber which would be better than an off the shelf die. If you notice a bulge near the web or rim then check for any incipient head separation, scratch test with a paper clip. If there is much of a bulge or any sign of separation get new brass. It may fire form itself to your chamber and be good to go.

Yes, it's safe to load and shoot them once, no problem there. I wouldn't continue to load with that small base die, but you already addressed that.

For a better understanding of the situation:

"Small base" dies size to a smaller diameter near the case head, as the name implies. The common "knowledge" that these are for semi-autos and lever actions is incorrect; in reality they are needed for a few very tight chambers (tight match chambers or just worn out factory reamers) and not much else. Normal FL dies are adequate and better for most rifles, with proper die adjustment.

If you do run across a rifle that genuinely needs a small base die, it's relatively simple most of the time to just open up the chamber with a normal reamer so that normal ammo and FL dies work fine.

Get a Redding Body Die (instead of a "FL" die) to go with the LCD. A match made in heaven.

+1 on MM suggestion

You can also turn the small base die into a body die by polishing out the neck portion to match the Lee collet along with opening up the base portion. This is the way I would go but a bump die is pretty inexpensive and even the Forester FL bushing die is not too bad. Where you want to spend your money is on the seater die. If I buy just the lee and then get a Forster competition seater than I am way ahead of buying multiple die sets and incrementally upgrading.