The generator matrix

 1  0  1
 0  1 5X
 0  0 5X+1

generates a code of length 3 over Z7[X]/(X^2) who´s minimum homogenous weight is 6.

Homogenous weight enumerator: w(x)=1x^0+126x^6+18x^7+5292x^12+1512x^13+108x^14+74088x^18+31752x^19+4536x^20+216x^21

The gray image is a linear code over GF(7) with n=21, k=6 and d=6.
This code was found by Heurico 1.16 in 0.0229 seconds.