I don't clean my rifle much, but always hate having to use a brush to scrub carbon off bolt and carrier. I just shoot,  relube the BCG, and put the rifle away for the next outing. I try to make an effert to do a detail cleaning about every 1000 rds. Been doing it like this for almost 20 years without issues.

I do a lot of mountain biking and have been soaking dirty bike chains in Simple Green overnight to get all the gunk and grim off it. I've had great success with it. Again, I hate having to use a brush. The chain is nice and clean the next morning. I just hit it with brake cleaner, apply lube, and I am off to the trails.

I was wondering if I can just soak the bcg overnight. If not Simple Green, are there other solvents that I can just soak it in that would take the carbon off without having to srub it?

Simple green aircraft formulation is better for aluminum, but should work fine.

don't use Purple Power !!! It took the bluing off a mod 39 marlin of mine..  If you watch the gunsmithing DVD's  that guy uses Simple Green on everything

Mineral Spirits from Home Cheapo. Just remember to dry and relube it.

It'll be fine on the bolt and carrier. Just make sure to completely rinse it off so it doesn't break down your lube or cause issues with the receiver. Simple Green is bad for aluminum so don't use it on the upper or lower.
My only fear is that since it has so much water it might rust.
I'd rather just get some mineral spirits or kerosene and mix it with alcohol and soak use that for an overnight soak.

I use a lab cleaner for cleaning fired brass etc., here in the UK called Micro Clean . Its been around for sometime - 30 years or and made here .Its a concentrate which you add to warm water .A few hours later job done ! Simply dry parts in cooling oven or hot sun.It made tumblers redundant .No noise ,no power ,no smell and leaves the sink spotlessly clean . It has no harmful products and uses a decomposing lifting action to remove grime to surgically clean standards with only occasional agitation .It has no detergents but does feel soapy and produces a few bubbles when agitated . A capful of concentrate is all thats needed.
I think it is exported as 'Micro 90' and should be available in the US .

Wow thanks for the Micro 90 recommendation. I will buy some to try.

I tried Simple Green but it is not safe for aluminum. It messed up the anodizing on a test part.

I had some Purple Power and tried that stuff and it did nothing except ruin the anodizing on aluminum. The stuff did not do anything to carbon, well it made it wet.

I found the Simple Green HD works pretty good at making carbon removable from BCGs. This stuff.

I usually break my guns down to clean after each range trip or at least every other. I disassemble the BCG, clean it then inspect everything. I know this is overkill but I actually enjoy cleaning my guns as much as shooting them.

We have a cleaning station that contains Simple Green; everything gets cleaned with it.

When I was in the military, we would give everything a good coat of CLP and put it back in the rack. Then next day everything came off quick and easy.