The generator matrix

 1  0  0  1  1  1  1  1  1  1  1  1  1  1 2a^2+2  1  1  1  1  1  1  1  1 2a  1  1  1  1  1  1  1  1  1  1  1 2a+2  1  2  1  1  1  1  1 2a^2+2  1 2a^2+2a+2  1
 0  1  0  1  a a^2 3a+3 a^2+3a a^2+3a+3 a^2+2a+1 2a^2+2 2a^2+3 a+2 a^2+2  1 3a^2+3a+2  2 a+3 a^2+a+2 2a^2+a+2 2a^2+2a+3 a^2+2a+2 2a^2+3a+1  1 a^2+a a+1 2a^2+a a^2+3a+1 2a+2 3a^2+2a 3a 2a^2+1 3a^2+2a a^2 3a^2+3a+2  1 2a^2+2a+2  1 2a^2+a+2 2a^2+a+1 2a^2+2a+2 2a^2+2a+1 3a^2+a+2  1 a^2+2a+3  1 2a^2
 0  0  1 a^2+2a+1  a 3a^2+3a+2  1 a^2+3a+3 2a^2+3a+1 a^2  3 a^2+a+3 2a^2+2 3a^2+2 a^2+2a+3 2a+1 2a^2+a+1 3a^2+a+2 2a^2+3a a^2+a+2 3a 3a^2+1 2a^2 2a^2+1 3a^2+a 3a^2+3 3a^2+3a+1 2a 3a^2+a+1 2a^2+2a+3 3a^2+2a+1 3a+2 3a^2+2a 2a^2+3a+2 a^2+3a+2 a^2+1 a^2+2a+3 3a 3a^2+2a+1 2a+2 a^2+a+1 3a^2+a 3a+2 a^2+3a+1 2a^2+1 a^2+2a 2a+1

generates a code of length 47 over GR(64,4) who´s minimum homogenous weight is 312.

Homogenous weight enumerator: w(x)=1x^0+4074x^312+2968x^313+56x^315+1904x^316+2800x^317+2128x^318+5432x^319+18487x^320+12600x^321+784x^323+12320x^324+10528x^325+4704x^326+7952x^327+29897x^328+19656x^329+2744x^331+28784x^332+18928x^333+7504x^334+11704x^335+37492x^336+18536x^337+63x^344+84x^352+7x^360+7x^376

The gray image is a code over GF(8) with n=376, k=6 and d=312.
This code was found by Heurico 1.16 in 9 seconds.