I think we're talking about a bit of gunnie mythology here. There's no inherent fragility in modern semiauto designs, especially not in AR pattern rifles. They are very robust.
The only way you would have a problem with commercial SAAMI spec 308 Winchester ammo in a semiauto rifle in terms of pressure is if the manufacturer fucked up and overgassed the gun (not uncommon in budget brand ARs). That would batter the gun and eventually damage it if not remedied. But any gun sold as a 308 Winchester should be able to handle commercial 308 Winchester ammunition or the manufacturer would be risking a major lawsuit.
If we were talking about military surplus 7.62x51mm rifles,
a lot more caution would be warranted. But we're talking new commercial guns here. They don't have military spec 7.62mm NATO chambers, they have SAAMI spec 308 Winchester chambers.
The real concern is bullet geometry, not power. A blunt round nose 308 round like you got on the old Remington Core-Lokt bullets might not feed well in any semiauto rifle that doesn't use a single feed magazine.
![[Image: 249807.jpg]](https://media.midwayusa.com/productimages/880x660/Primary/249/249807.jpg)
Old vs new
Certain soft point designs can also get mangled on the feed ramp; my AR-180B was terrible about chewing up the Black Hills 223 Remington soft points I used for varmint hunting, for example. The exposed lead tips would get totally chowdered on the feed ramp every time. No big deal as long as I shot them once I chambered them. They were just ruined for feeding from the magazine again.
There is other stuff to worry about if you reload for a semiauto rifle, but that's outside the scope of this discussion.
So yes, I agree you do have to take a bit more care in selecting ammo but it's not because the ammo is too powerful for the gun. 308 Winchester is 308 Winchester, this isn't like the 45-70 Gov't or 45 Colt situation where there are two tiers of ammo power available, and if you pick the wrong one you're going to blow up your gun.
For what it's worth I've owned three semiauto 308 Winchester rifles, two Springfield M1A Scouts and a DPMS LR-308, which all saw significant round counts. The only problems I ever had in those guns were with shitty berdan primed surplus 7.62x51mm that was underpowered, which often short cycled the guns. Commercial 308, Lake City surplus, Lithuanian surplus, reloads at commercial velocities... the guns all ran like sewing machines.