The best stuff I have found is CVA BREECH PLUG AND NIPPLE GREASE. I have tried a lot of them and IT IS THE BEST. Another thing to do is, never tighten the breech plug in all the way. Tighten the plug in and then turn it off a 1/4 turn. After about 5-8 shots, take your wrench and give the breech plug a turn. Work it back and fourth. I do this every 10 shots afterward while swabbing and other duties like wiping out the breech/nipple area. This will make sure it is not seizing up. You will have no more problems.

If your at a range and going to have a long drive home, be sure and loosen the breech plug before you start your trip.