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  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  7  1  1  1  7  1  1  1  1  7  1  1  1
 0  7  0  0  0  7  7 28  0 21  7 42 14 42  0 28  7 42  7 28 28 35 28  7 14 14 28 35 28 42 42  7 14 42  0  0 35 28  7 42 42 14 14 14  7  7  7 28  7  7 42 28 28 21  7 21  0  0
 0  0  7  0  0 35 28 35  7 28 35 35  7  7  7 21 42 21 21 35  0 28  0  7  7  0  0 42 21 14 42  7  0  7 35 35 21  7 28 14 35  0 28 35 35 35 28 21  7 28  0  7  0 14 42 42 21  0
 0  0  0  7  0 35 21 21 35 35  7 42  0 14 42 21  7 21 21  7  7  0  7 14 35 35 21 42 35 28 21  0  0 35  0 14  0 42 21 21 35 14 35  0  7  7 42  0 28  7 14 42 14  0  7 28 14  0
 0  0  0  0  7 35 42  7 42  7  7  0 14  7  7 42 28  0 28 14 21 35 42 35  7  0 14 21 28  7  7  0 14  0 42 21 14 42 21  0 28 21 35  7 21  0 21 35 14  0 42  0 35 28 21  7 21 21

generates a code of length 58 over Z49 who´s minimum homogenous weight is 308.

Homogenous weight enumerator: w(x)=1x^0+78x^308+762x^315+1476x^322+1596x^329+294x^330+1746x^336+5292x^337+2220x^343+31752x^344+2226x^350+63504x^351+2178x^357+1764x^364+1446x^371+798x^378+414x^385+90x^392+12x^399

The gray image is a code over GF(7) with n=406, k=6 and d=308.
This code was found by Heurico 1.16 in 12.9 seconds.