I've used Mpro 7 cleaner since day 1 and no problems at all. It works great and you can use it in the house with no issues. After using Mpro 7, I use q tips to clean out the rails that support the bolt and then use a bore snake (very rarely) and then some Mpro 7 CLP <-- awesome stuff.

I've noticed the same grit problem that was mentioned earlier. Once I switch to Mpro CLP it got much better.