I will throw this out here for S&G...and flame if you like...
One of my Colt Gold Cup 45's had lead fouling when I bought it [used]...Not a lot; just a little...I asked an old shooter how to get it out...he said to just shoot a FMJ slug through it...It sounded like a fairly drastic remedy, but since I shoot FMJ's anyway, I tried it...he was right...It cleaned the lead residue out...
Now, I'm not recommending it for this particular case...or for any case, for that matter...Just passing along an old pistol shooters ramblings...YMMV...