MLT MADE 270 DEGREE TURN WHILE DEVIATING FOR WX AND NEARLY CAUSED LOSS OF SEPARATION WITH FOLLOWING MLT.

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MLT X; SID DEP NBND; LEVEL 10000'; REQUESTED CLB FOR WX. I WAS UNABLE TO ISSUE CLB; BUT APPROVED A DEVIATION FOR WX; LEFT OR RIGHT. MLT X WAS SUBSEQUENTLY TRANSFERRED (COMS AND RADAR) TO CENTER; LEVEL 10000'. MLT Y; SAME SID DEP; NBND; LEVEL 10000'; 6-7 MI; INTRAIL OF MLT X. MLT Y REQUESTED CLB FOR WX. AGAIN I WAS UNABLE TO CLB BUT APPROVED A DEVIATION TO THE LEFT ONLY. MLT X STARTED A RIGHT TURN TOWARDS AN ENRTE FIX (CEW) AS FILED; BUT CONTINUED A RIGHT TURN TO A 270 DEG TURN COMING BEHIND MLT Y WITHIN 2.5 MI; BOTH AT 10000'. PLT OF MLT X TOLD CENTER CTLR THAT APCH HAD APPROVED A DEVIATION TO THE S. I ADVISED CENTER CTLR TO ISSUE MLT X A TURN SW (240 DEGS) AT 10000' AND RADAR CONTACT. MLT Y WAS TURNED RIGHT DIRECT CEW AND SWITCHED TO CENTER. MLT X WAS GIVE SAME INSTRUCTIONS AND SWITCHED TO CENTER ALSO. RECOMMEND: CTLR SHOULD BE MORE SPECIFIC WHEN ISSUING DEVIATION APPROVAL; IE; ONLY SO MANY DEGS LEFT OR RIGHT FOR SET AMOUNT OF TIME; ETC. ALSO ENSURE ACFT IS ON COURSE BEFORE CHANGING RADIO TO ANOTHER FAC; OR ADVISE OF DEVIATION. FLT CREWS SHOULD NOT EXPECT THAT THEY CAN DEVIATE GREATER THAN 30-60 DEGS W/O FURTHER CLRNC TO DO SO. SURELY NOT A COURSE REVERSAL OR 270/360 DEGS! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: WHEN RPTR ADVISED HIS SUPVR THAT THERE HAD BEEN A PROB WITH SEP BTWN MLT X AND MLT Y; THE FAC REMOVED RPTR FROM OPERATIONAL DUTIES AND STARTED AN INVESTIGATION. AN NTAP SHOWED THAT THE SEP BTWN THE 2 ACFT WAS 2.5 MI AT THE SAME ALT. THE FAC DETERMINED THAT AN OPERROR DID NOT OCCUR; HOWEVER BECAUSE THE SECOND MLT WAS ON APCH CTL FREQ AND THERE WAS LEGAL COURSE DIVERGENCE SEP; RPTR WAS COUNSELED BY FAC MGT FOR NOT BEING MORE SPECIFIC IN HIS INSTRUCTIONS TO MLT X AND MLT Y WHEN ALLOWING THE WX DEVIATIONS. THE CTLR; IN EFFECT; GAVE THE 2 FLT CREWS CARTE BLANCHE BY ALLOWING A NON SPECIFIC DEVIATION FOR WX. DURING THIS INCIDENT; BOTH ACFT REMAINED IN PNS AIRSPACE WHILE MLT X WENT TO ZJX FREQ AND BACK TO PNS FREQ DURING THE TURN FOR WX. MLT Y STAYED ON PNS FREQ FOR THE DURATION OF THE INCIDENT. RPTR IS CORRECT WHEN HE SAYS CTLRS SHOULD BE SPECIFIC WHEN THEY ALLOW DEVIATIONS FOR WX WHEN MORE THAN 1 ACFT IS INVOLVED.