ROME (AP) _ The man who shot Pope John Paul II today refrained from the irrational outbursts that marked his previous testimony in the trial of seven men accused of conspiring with him, and calmly told a court how he became a terrorist.

''My terrorist activity never provoked an innocent death ... I never killed anyone,'' said convicted gunman Mehmet Ali Agca, now being tried on a charge of smuggling into Italy the gun he used to shoot the pope.

The 27-year-old Turk, speaking in slow, concise Italian, also began detailing an alleged international plot to kill the pontiff and other terrorist activities in which he took part.

The prosecutor has charged that Bulgaria, possibly with Soviet support, masterminded the assassination attempt because of John Paul's support for the Solidarity free trade union in his native Poland.

Agca had been called to the stand twice before in his joint trial with four other Turks and three Bulgarians, who are charged with complicity in the May 13, 1981, shooting of John Paul in St. Peter's Square.

Both times Agca refused to testify, instead making irrational outbursts, claiming to be Jesus Christ.

Agca sat calmly today, clutching a tiny Italian-Turkish dictionary.

In response to questioning by Judge Severino Santiapichi, Agca said he bought the Browning pistol used to shoot the pope from two Vienna, Austria arms dealers named Otto Tinter and Horst Grillmayer.

Agca said he was accompanied by Oral Celik, also Turkish, who is being tried in absentia on the conspiracy charge. Agca said Celik bought four identical Browning 9mm pistols.

Asked why they bought the guns, Agca replied, ''Because we wanted to resume our terroristic life.''

Agca said he became interested in right-wing ideology while still in his hometown of Malatya in eastern Turkey. He said he made contacts with the right-wing Gray Wolves organization in the Turkish capital of Ankara.

The judge asked Agca if he shared the Gray Wolves' right-wing philosophy.

''Not really,'' he said. ''It was an organization of extreme rightists, nationalists and anti-Communists, but also adventurers and criminals.''

He denied killing a liberal Istanbul newspaper editor, Abdi Ipekci, on Feb. 1, 1979. Agca was convicted and sentenced to death in Turkey in absentia for the murder, to which he originally confessed. He later retracted his testimony in Turkey before he escaped from a military prison and fled the country.

Pressed to say who was behind the killing, Agca replied, ''I cannot say anything more because some hidden power is involved.''

''What do you mean by hidden power?'' the judge asked.

''Hidden power means linked with the state,'' Agca replied, refusing to give more information.

Agca said his escape on Nov. 23, 1979, from a top security prison in Turkey was arranged by Celik.

Today's session adjourned with Agca still on the stand. Agca first insisted that he acted alone in the papal shooting but then turned state's evidence, and told prosecutors about a plot he said involved Bulgarians and other Turks.

He took the stand after another Turkish defendant, Omer Bagci, ended his fifth day of confused and contradictory testimony. Bagci admitted taking the pistol used to shoot the pope from Switzerland to Milan at Agca's request, but inisted he did not know Agca's plans.

Agca and another Turkish defendant, Musa Serdar Celebi, were kept out of the courtroom during Bagci's testimony.

The only Bulgarian defendant in custody, Sergei Ivanov Antonov, looked on passively from his metal defendant's cage as Agca spoke. Two other Bulgarians are being tried in their absence.