Yes, Brahmins performed such rituals which turned non Kshatriyas to Kshatriyas.
One such instance is Hiranya Garbha (literally Golden Womb) ritual performed by Dantidurga, who is the founder of Rashtrakuta dynasty who overthrew Chalukya Dynasty of Karnataka. He was not a kshatriya by birth but turned to a Kshatriya after performing this ritual.
Hiranya Garbha Mahaadaana is one of the sixteen Mahaadaanas.
Tulapurusha
Hiranyagarbha
Brahmanda,
Kalpapadapa,
Gosahasra,
Kamadhenu (or Hiranya-Kamadhenu),
Hiranyasva,
Hiranyashvaratha,
Hemahastiratha,
Panchalañgalaka.
Dhara,
Vishvachakra,
Kalpalata (or Mahdkalpalata),
Saptasagara,
Ratnadhenu and
Mahabhütaghata,
Among these Rulapurusha and Hiranyagarbha maahaadaanas are famous
Dantidurga performed a ritual at Ujjaini named Hiranya Garbha which is believed to give a rebirth to the sacrificer who performed it. It will be considered as a new birth from that moment.
Matsya Purana Chapter 273 and 274 are dedicated to explain these above two rituals in detail.
By performing the ritual, the sacrificer gets a rebirth and the samskaras like Garbhadana, Punsavana and Simanta are done to the Hiranyagarbha. All the sixteen sacraments are performed to the devotee by the brahmins. After this, the brahmanas chant some mantras and that is considered a new birth to the devotee performing the mahaadaana.
O Best of the Devas’ as I was born of you in the mortal world so let me be born again of Divine form on account of my being born again of you.. You have created me virtuous and trut1iuI. Afterwards the Brähmana should
dccorte a blessed cow with the ornaments and bathe her with four Vases. He should sear her on the golden seat and bathe her by reciting these
mantras, viz.•- “Devasya tvá” etc. and say “I shall now bathe all the limbs born of you” [Chapter 274 verses 20-22]
From new world encyclopedia site,
The Sanjan inscriptions tell of King Amoghavarsha I sacrificing a finger from his left hand at the Lakshmi temple at Kolhapur to avert a calamity in his kingdom. King Dantidurga performed the Hiranyagarbha and the Sanjan and Cambay plates of King Govinda IV mention Brahmins performing such rituals as Rajasuya, Vajapeya and Agnishtoma.
Dantidurga performed Hiranyagarbha ritual and it is recorded in the Sanjan inscriptions. After that, other kings also accepted him as a Kshatriya and he became a powerful ruler.