How to use 762-SD SUPPRESSOR

[mmff]

I would like to install the 762-SD SUPPRESSOR on my M700, but I am told that there is no space so I cannot install it. I can attach it by removing the scope, but how can I attach both?
GUNNY's rank is still 1, so do I need to rank it up?

[Cryptic]

Its telling you to move it to a bigger space in your inventory locker. The slots required go from 5 to 6 when adding the suppressor

[Sir Fitzgerald]

You need the M700 Picatinny rail from Banshee in order to attach the scope to the m700. You can also get the rail from M700 snipers you loot from crates. In order to attach the suppressor to an m700 you need to use SRD762-QD FLASH HIDER in conjunction with the 762-SD Suppressor and the m700 Barrel - 22".
The M700 suppressed Barrel - 20" and the M700 VTR - 22" barrel don't seem compatible with barrel attachments. All purchasable from Banshee level 2 and the Rail is also purchasable from gunny level 2