The conventional narrative of the air war in Europe, is that the P51 was the fastest and longest ranged fighter of the war, and that we didn't have fighters with the escort range necessary to escort bombers all the way to their targets and back, until the arrival in quantity of the P-51C, and P-51D with the 8th air force at the end of 1943 and into early 1944 (P51s officially started escort missions in January 1944).
This narrative is repeated in countless histories and documentaries... it was even part of the official 8th air force doctrine reference and history.
It's also completely false.
In actual fact, as used in the field, the P47 (particularly the later bubble canopy models) was both faster (higher turbosupercharging boost pressure and better cooling, with higher octane fuel and new props, and new venting systems, plus new understanding of how those interacted and development of optimal settings for them improved speed and fuel economy in the field by more than 20% over official sources), and had longer range than the P51 when both were equipped with drop tanks.
Of course, it took more than twice as much fuel to get there... But with the available drop tanks from late 1942 onward, and the upgraded internal fuel capacity available in early 1943 (upgraded from 305 to 370 gallons internally, and twin 150 gallon wing tanks with a 200 or 210 gallon belly tank), the P47 had a full 770 mile escort radius available to it (and a non escort range of over 1900 miles with optimal fuel management) if the generals in charge of the bombing raids had chosen to use those tanks. And a few months after that, their escort range could be as high as 910 miles.
...(an aside, the later mustangs were upgraded from 180 gallons internal to 269 gallons internal capacity, and had twin 110 drop tanks available to them, and a 168 gallon belly tank which was suitable for ferry use but not for combat. With those tanks they had an official 2,080 mile range...in reality with optimal fuel management that could be extended to something around 2,280-2,340 miles. However, the P47 had available.. though they were rarely used... twin 300 gallon tanks plus a 210 gallon belly tank with which it WAS combat capable... a combined total fuel of 1180 gallons in the configurations used in Europe... and which given optimal fuel management could extend its range... depending on atmospheric conditions at altitude [because they effected turbocharger settings] to between 2,360 and 2,480 miles... though officially it never had more than a 1,990 mile range, because it was politically important that the mustang have the higher official range number.
Further, the P47n used in the pacific, had vastly increased internal fuel capacity... ultimately a total of 810 gallons internal, which combined with twin 150 wing tanks and 210 belly tanks [they couldn't use the 300 gallon wing tanks because most of that new internal fuel capacity was in the wings, and the additional weight would have caused structural problems], gave it an escort radius of over 1100 miles, and an ultimate non-escort range of well over 2,400 miles... the longest documented range ever achieved being appx. 2,700 miles point to point, but with navigational uncertainty and course variations, could have been as much as 2,840 miles actually traveled)...
Instead, from the beginning of the war, until the very end of 1943, use of those large drop tanks was banned. In fact, throughout all of 1942, the 8th air force officially banned the use of drop tanks at all, for anything but ferry flights, though there is ample evidence that by the end of 1942 this ban was being widely ignored... and in early 1943, the use of 75 gallon drop tanks was finally authorized. Later in 1943, they authorized the use of the English 108 gallon drop tanks (made of compressed paper saturated with resin, in a bicycle and fender shop near the air base they were developed at by the by). However drop tanks were in short supply because of the official ban, and it took months and months for the supply of drop tanks to build up to usable levels after the ban was lifted.
This ban, and all that followed from it, was a stubborn insistence on the part of certain bomber mafia generals, to refuse to admit pre-war doctrine (which said that fighters couldn't effectively escort bombers long distances, and therefore the bombers should defend themselves) was false, and a refusal to accept responsibility for the loss of life caused by this doctrine.
They were able to escape this humiliating admission, by falsely claiming that they just didn't have aircraft with the ability to escort the bombers until the P51 was available in large numbers, with its drop tanks.
... So... As the P47 was actually used, by doctrine, the P51 was indeed faster and longer ranged... but in reality, in their combat conditions in the field, the P47 could be faster and longer ranged.
... At least up until the very end of the war, and really until after the active combat in the European war was over, when some final engine and turbocharging changes, and the final drop tank configurations available, finally made the P51 faster than the P47 as used in Europe and with longer ranged than the P47 as used in the European theater... but it was never faster or longer ranged in combat configurations, than the P47N used in the pacific.
... Only after the war, in stripped down configurations used to set records, using special high performance props, and turbocharger settings never allowed during the war (and then later in Korea when further developments in engine management, turbocharging, high octane fuel, and bigger better props made it even faster and more efficient) was the MUCH more aerodynamically efficient P51 actually faster than the fastest of the P47s.
I give Hap Arnold a lot of credit for a lot of things... He more than earned his legion of merit and distinguished flying cross, and he is recognized as the founder of the modern air force for good reason. I will never deny the man was critical to that foundation.
... But on this one issue, he royally screwed the pooch... and at least 10,000 men died, who probably didn't have to die, because of it.