benelli m2 20ga question

[jeubank3]

Went out today to test out the Sumtoy 562-5 choke I got for my Benelli M2 20ga.  I got the M2 for 35% off right after last turkey season when Gander Mountain went under.  All I've done with it until today is shoot a half round of clays, but it's a sweet shooting little shotgun. 

So, I set up some poster board targets at 40yds with a 10" circle drawn on.  I shot a couple of light loads just to check my POA/POI.  My POI was off a bit high, but I'm chalking that up to inexperience with the weapon, higher powered loads, and to the fact that I default to shooting high when I mess up my form.  Next I put 4 rounds of FHW 7s 3" 1-1/2oz down range on the poster boards.  First two shots impressed me a lot.  Circling the highest density area of the board, the 1st shot had 218 in the circle, and the next had 211.  After that, the 3rd shot only put 169 in the circle, and the 4th dropped even lower to 114.  No strings showing up, just a much looser pattern.  No way the highest density was off the board, it was just looser everywhere. 

Being as I'm inexperienced with all 3 parts of this shooting equation (new gun, new choke, and 1st time using this ammo) I'm wondering about the drop in the pattern density.  For those who have shot this combo, or at least the m2 20ga, do they fall off quickly without cleaning?  I would have run the bore snake through and tried another shot if I had taken it with me and had another poster board .  If not that, I know some folks commented on here about some issues with certain production periods of the FHW shells having issues, could that cause that inconsistency?  My instinct tells me I just need to make sure to keep that barrel super clean all the time. 

Thanks,
James

[SumToy]

I would brush the barrel to see.  Plus I dont know with the heat how much it hurts them if you shot very fast.  I know normal Bird shot will go crazy if barrel heats up.   Plus was all shells out the same box.

[davisd9]

Probably just need to keep barrel clean.  My 835 was that way, after 4-5 shots the pattern would not be as even and the high part of the pattern is where the shot was.  Would clean and she would even back out. I would clean it after every third bird or third shot.  Those wads leave a lot of residue in the barrel.

Benelli is known for not shooting POA.

[jeubank3]

Thanks guys. All shells out of the same box. I took enough time between shoys to walk the 40yds, eyeball results a bit, take it down, staple a new one up and walk back. I don't think overheating would have been the issue. Gave it a good cleaning, so we'll see this weekend.  I was really surprised at how fouled the barrel was. Looked to me like more in the barrel from those 4 shells than from 60 or so target loads on the other outing.