I was shooting Remington Thunderbolt ammo in my SR 22 and I had an excess amount of lead buildup/fowling in the muzzle end of the barrel. The first time I used this ammo I fired 100 rounds and not a problem with fowling or grime and easily clean the gun with hoppes #9 and patches. The next time I fired the gun after only 60 rounds I noticed the buildup. Also this Box of ammo I used had three failure to fire. I ejected the rounds and when I reloaded the Mag. I used the rounds that did not fire. This time they worked fine. I stop firing and returned home to clean the SR 22 and that is when I found the excess lead fowling. I used a brass cleaning brush and CLP spray then used a lot of Hoppes #9 finally the lead deposit came loose and I was able to clean the pistol. After an hour and a half the pistol was cleaned and oiled feed ramp was smooth and all seems well. Has any one ever experinced such bad fowling of the barrel as I have discribed? Did I pick up some bad ammo? I really thought I had damaged the barrel. Any and all help please. Thanks as this has never happen before in any gun I have shot.