They were extremely useful and much in demand. Deployed primarily in the ETO with paratroopers fighting on the ground as elite infrantry they had great success vs both enemy armor and fortifications. Also deployed in the PAC with marines...
To set the record straight, the recoiless rifle used by the paratroopers in the ETO were
shoulder fired 57mm versions, not larger ones mounted on jeeps. During the battle for Okinawa, the Marines used the 75mm M20, which was designed to be used on a tripod mount.
Whether the Marines used a
jeep mounted RCL has been debated in a couple of other threads. The closest anyone has come to offering anything in the way of proof was Hornet33 (iirc), who posted a personal pic he got from an uncle I believe. Unfortunately, it does not have any context as to exactly when and where it was taken. The closest I personally had come through web-browsing was a picture of jeep mounted M20 recoiless on a French-owned jeep -- taken in 1947.
I would love to be wrong, but I just don't believe a jeep mounted RCL was used in WWII.
