View Full Version : Dirty Barrel

April 9, 2008, 11:58 AM
I have A 20ga. Thompson Center Encore shotgun. It seems that after I clean the barrel it takes A couple of shots before it starts to shoot A nice pattern. It seems to shoot better with A dirty barrel. Is this normal and what causes this?

April 9, 2008, 12:45 PM
This is caused by barrel fouling. Most guns will shoot better with a couple shots run thru them first. Basically, the rounds fired cause the imperfections in the bore to be filled with residue thus making a barrel more accurate. I myself tend to always fire a couple fouling shots thru my rifle and slug gun before going hunting to ensure the poi is the same as when I left the bench.(never noticed a difference with birdshot) Sometimes I wont clean the bore at all depending how bad it is fouled. Also, a big help with accuracy for a rifle is to follow a good break in procedure for a bore. Typically, 100 rounds will do the trick with clean patches run thru between every other shot. Try a couple different brands and sizes to see if it improves the pattern.

nutty ned
April 9, 2008, 07:33 PM
I find this strange in the day of shot cups. I do not notice any difference in my shotguns.

April 9, 2008, 11:04 PM
Interesting. Our routine is to usually shoot about 25 rounds at the practice traps before moving on to the sporting clays course. I am going on a patterning expedition this Sunday, and I will try to pay attention to this. I am patterning 4 shotguns with 3 different loads, and 3 choke tubes each, so there will be plenty of opportunity to test out the theory.

Just from a logical perspective, I must say that unless the bore is in poor shape, I can't really buy into the concept. The bores on my shotguns are pretty much "mirror like", and that doesn't leave many places for residue to build up. That doesn't mean it isn't right, it just doesn't make logical sense to me.

April 10, 2008, 06:47 PM
What kind of barrel?:confused:


Scattergun Bob
April 10, 2008, 10:14 PM
Truly, your gun is one of the few shot throwers I have no experience with. I am somewhat interested in this as a sideline player, with no knowledge to help.

Question: have you gathered this info from patterning you gun or is it just not knocking hell out of stuff first couple of rounds. It would be interesting to do some pattern boards on this issue and describe the difference.

Good Luck & Be Safe

April 11, 2008, 08:29 AM
Just an fyi. My friend has the same gun and we went to shoot it again last night. We cleaned it good and shot a box rounds and found for some reason it did pattern better dirty. I have patterned many shotguns with birdshot and never noticed a difference except with this one. It wasnt a major difference but it was a little better dirty. I know with rifles and slug guns this is common and they shoot better with a few rounds thru them. Im going to try a few other shotguns today and see what happens. I will post later to let you know what I come up with. I am going to pattern with a Rem. 870 (new), Mossberg 500 (old), Browning Gold 3.5(newer), and an Ithaca 37(oldest). I am going to use #6,#4, and 00 buck.

April 11, 2008, 12:11 PM
Just thinking out loud here. Is the issue really whether it is dirty, or is it that it is warmed up? Be interesting to not clean it between sessions, and see if it improves with a few rounds. that would indicate warm up rather than dirt. All interesting conjecture, but really of no real value. Just run a couple of practice rounds through it and go to town.