Never reloaded for a semi automatic. What dies do you need? I saw Lyman has a three die carbide set. Is that a good choice?

I have RCBS dies and one set has the small base sizer die for semi autos. From what I have loaded, I don't really need the small base die---all of my AR's function just fine with regular sizing dies. I have not tried the carbide dies. I just ordered the caliber conversion and die set to load 223's on my 550B Dillon.

All 6 of my AR's and my AR 10 work just fine with regular dies and my AR 10 is more accurate than most bolt action hunting rifles. I've never tried the Lyman carbide dies for the AR's.

Steve E........

I have small base dies for my 6.8 & 338 fed AR-10. I've never reloaded 556, bought enough when it was $179/case. So now, I have to start with 308. Picked up a 308 Scar last year. I got 308 Lapua brass and going to pick up SSA 762x51 mil spec brass. Got my primers & powder. Now I need dies. I'm going to buy RCBS dies. Should I get carbide? Should I get small base for 308. I figure 308 & 762x51 are the same. Should I get Lee crimp die? All the reloads will be used in ARs of 308 caliber. What do you all suggest?

A quality AR with a good chamber does not need any "special" dies. I load 223, 260, 308 and 300 SAUM ARs using plain old Lee dies and even use the collet neck sizing die for the first three.
This is also true of my R1, SR1 and even M-1 (National Match).
There is more BS about semi-autos as most shooters have ZERO experience with them and just repeat what some gun scribe wrote sometime that has been repeated w/o any questions.

As for RCBS, they can't even make the correct sizing die for a 7.5 Swiss.......

All a small base die is, is a cure for a sloppy out of round chamber. The ONLY rifle I have ever owned that required them was a 1944 built G43 that was at best a crude piece of work (but fun).

X2 I never used the small base dies for my HK91 type or the .223. But I have used them on once-fired Lake City 7.62 cases to prep for running them into a 358 Winchester die. I just thought it an insurance thing to get them to specs before conversion to 358. Just get a set of dies and always use proper lubrication.

If the brass you are using was new and only fired in your gun than you will be able to get by with regular dies.
However if you are using once fired brass (5.56 or 7.62) such as Lake City / military brass than using a small base die is the smart way to go. When using LC brass there is no way of knowing if it was fired in a machine gun like a M240 or M249 with a loose chamber etc. If fired from a machine gun than more than likely the brass will be oversized by the case head and this will need to be resized and the best way is to use a small based die.
I use a small base dies for both my AR 15 and my M1A and never have to worry about one jamming up in the chamber because it won't fully enter the chamber.