Found this on a site...
4th Fighter Group
Assigned 8th AAF: 12 Sep 1942
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Combat Aircraft:
Spitfire V: Sep 1942 to 1 April 1943
P-47C 10 Mar 1943 to Feb 1944
P-47D Jun 1943 to Feb 1944
P-51B 25 Feb 1944
P-51D Jun 1944
P-51K Dec 1944
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http://www.usaaf.com/8thaf/fighter/4fg.HTM *
The new P-51B/C was used in 15 fighter groups. The groups were in the
8th and
9th Air Forces in England and in
12th and
15th Air Forces of USAAF* in Italy the European Theater December 1943. They also entered service China-Burma-India (CBI) September March 1943 Mustangs were used as escort fighters to B-17 "Flying Fortress" and B-24 "Liberator" bombers bomb Berlin.
P-51 D/K and the further historyThen, finally, the P-51D/K appeared. It is the most known version of "Mustang". There was an opportunity to improve the disadvantages of the P-51B/C version, for example its limited firepower. Finally three 0.5 inch (12.5 mm) machine guns were installed in each wing. The inboard guns had 400 rounds each and the other guns had 270 rounds each. There was also an option to remove two of the guns, and retain just four with 400 rounds each. There were additional modifications of the landing gear and wing design. The problem with installation of another fuel tank was fixed in some planes too. 7956 planes of this type were produced (6502 in Inglewood and 1454 in Dallas). The difference between K and D versions was in the armies they arrived: P-51K was built for the United Kingdom, while P-51D was built for USAAF. Another minor difference was in the propeller (it did influence the performance, though). The P-51D began to arrive in Europe in March 1944.
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http://www.geocities.com/CapeCanaveral/Hall/3604/chap2/chap2.html *