The generator matrix

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

generates a code of length 39 over GR(64,4) who´s minimum homogenous weight is 248.

Homogenous weight enumerator: w(x)=1x^0+259x^248+56x^252+798x^256+1176x^260+728x^264+8232x^268+679x^272+19208x^276+546x^280+413x^288+448x^296+189x^304+35x^312

The gray image is a code over GF(8) with n=312, k=5 and d=248.
This code was found by Heurico 1.16 in 0.376 seconds.