My code:
.h
UPROPERTY(EditAnywhere)
AActor *BulletTemplate = nullptr;
.cpp
std::wstring name = std::wstring(L"Bullet_") + std::to_wstring(itemNum++);
UObject *outer = BulletTemplate->GetOuter();
AStaticMeshActor *bullet = DuplicateObject(Cast(BulletTemplate), outer, name.c_str());