I assume by "large" you mean heavier than the classic 55 grain as opposed to a larger diameter?
Both the AR15 and bolt .223s originally came with a 1-12" barrel twist rate tailored to the original 55-gr FMJ-BT M193 bullet. Starting in the 1980s efforts were made to improve downrange performance and penetration. FN came up with the SS-109 62-gr FMJ-BT bullet and we decided on using it (but called the M855). To shoot this new longer and heavier bullet the 1-12" M16 A1 was phased out and the 1-7" twist M16 A2 and M4 Carbine were phased in.
Match shooters then started to experiment with heavy match bullets since the new 1-7" twist rate would stabilize them and they offered better wind-bucking performance in match shooting with a trajectory matching the .308 Match round. They found that 1-7" would stabilize even 80+ grain bullets. Therefore a whole slew of heavy match bullets are available.
There are also .223 twists of 1-8" and 1-9" besides the old 1-12". The light bullets will stabilize and shoot okay in the quick twist barrels, but the heavier 62+ grain bullets will not stabilize and will keyhole when used in too slow of a twist. This in itself is not dangerous - just inaccurate. For the last decade or two virtually all AR15s come with either a 1-7, 1-8, or 1-9" twist rate - so this range can now be considered normal AR15 barrel twist - so I would say that NO they don't have a different barrel for heavier/longer (or larger?) bullets.
You need to keep in mind that no matter what bullet weight from 40 to 80 is used in commercial .223 loads it is loaded to similar pressures thus making the loads safe - just like in the 30-06 that is loaded with bullets from 110 to 220 grains. So barrel pressure isn't an issue.
What is an issue - and may add some confusion - is that SAAMI .223 Remington chambers (mainly found in bolt-actions) differ from NATO military chamber that virtually all AR15s use. So military ammo, whether 55-gr M193, or 62-gr M855/SS-109 may have the bullet impinge a bit too much in the .223 SAAMI chamber and cause excessive pressures. In addition, M193 and M855 with their new brass and crimped-in primers is loaded hotter than SAAMI .223 and this may cause an issue in non-NATO chambers. However, as mentioned, virtually all AR15s are made for hot military ammo fortunately.