Yes, everything I've been told over the years says that you shouldn't shoot with any obstruction in the barrel, including oil, lead etc, but I wonder to what extent this applies. I too have heard of people shooting the lead fouling out of rifles with copper projectiles, but I don't know how bad the fouling was. (I also have seen and heard of people shooting the oil out of their barrel, I wouldn't try this, without damage but less that ideal accuracy for this shot, if fact a 6.5x55 projectile hit the target completely sideways in one instance.)

Some say that shooting the oil out will "ring" the barrel and it probably has done, as will a patch left in the barrel (actually, I've got a copy of Hatcher's Notebook at home and I recall he did some barrel obstruction experiments - I'll have to have a look at it on the weekend).

The only "ringed" barrel I've seen was in a 22 semi-auto that must have had a projectile stuck there from a previous mis-fire (ruptured case event, somehow went off before the bolt was fully home). The next round blew the stuck projectile out and created the ring. It wasn't evident until later when we noticed the new external profile of the barrel. It didn't affect accuracy after that - lucky I guess, nice symetrical ring.

I've seen stainless steel bore brushes for sale but would be nervous about using one of these and damaging the barrel.

I was hoping to avoid manual labour - lazy but also want to minimise the risk of causing any damage while doing so. I've got an ex-mil Mauser that had the muzzle end of the rifling removed by over-zealous and incorrect use of a pull-through (apparantly). Carbon on cloth is a killer.

On the other hand, mercury is supposed to dissolve lead - anyone willing to "lend" me a recoil reducer for a little while, I'll give it back when I'm finished