[bluefin556]

I wanted to add the alloy quad rail to my sig 556 scm. Sig told me I had to send it to them for it to get done. They said they have adjust the gas block or somehting. Is this bs? Dont you just take one off and put the other one on?

 

[gospeedracergo]

That is all you should need. Took my fish gills and installed samson.