ACR X UNABLE TO MEET ALT RESTR AT INTXN BECAUSE OF RADAR VECTORS.

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AT APPROX 57 DME FROM WALET INTXN AT 15000 FT MSL WHILE TRACKING THE 352 DEG RADIAL FROM SQS VOR; WE WERE GIVEN THE XING RESTR OF WALET AT 6000 FT. THE CAPT (PF) THEN INITIATED A SLOW 500 FPM DSCNT. AT THIS TIME; BECAUSE WE WERE SLIGHTLY E OF COURSE; WE WERE GIVEN A HDG OF 340 DEGS TO INTERCEPT THE MEM 225 DEG RADIAL AND CROSS WALET INTXN AT 6000 FT. SOON THEREAFTER; CTR GAVE US A HDG OF 335 DEGS TO INTERCEPT. AFTER COMPANY CALLS AND CHKLIST WERE COMPLETED. I NOTICED THAT THE CAPT DID NOT INCREASE OUR DSCNT RATE. WE WERE AT 11000 FT AND APPROX 12 DME FROM WALET. I VISUALLY LOOKED OUTSIDE AND SAW THAT WE WERE WELL E OF THE VISUAL LANDMARKS THAT ARE EASY TO DEFINE WALET INTXN; THEREFORE WE STILL HAD AT LEAST 20 MI TO INTERCEPT THE 225 DEG RADIAL AND WOULD NEVER CROSS WALET INTXN. THE CAPT INCREASED HIS DSCNT AND CTR THEN TURNED US TO A HDG OF 360 DEGS. WE CROSSED 30 DME SW OF MEM VOR AT 6000 FT; HOWEVER ATC ASKED US OUR ALT AND QUERIED US ABOUT OUR RESTR. NOTHING FURTHER WAS SAID AND THE FLT LANDED UNEVENTFULLY. I SEND THIS SIMPLY BECAUSE I AM PUZZLED BY ATC AND THEIR PERCEIVED IRRITATION WITH OUR RESTR. ALTHOUGH GIVEN 3 HDG CHANGES; NONE OF THE VECTORS GIVEN BROUGHT US NEAR WALET INTXN. OUR ONLY MEANS OF DETERMINING WALET (225 DEG RADIAL MEM; 29.7 DME) WAS USELESS BECAUSE OF BAD VECTORING. OUR ONLY OTHER RESOURCE WAS TO MEET THE DME DISTANCE WHICH WE DID 30 DME SW OF MEM VOR.