Wingmaster Rifled Barrel Sight Adjustment

[ABL1111]

Bought a used rifled barrel for my late 1950's 12 gauge Wingmaster. The gun looks almost new. The barrel also looks quite new. I use a scope almost always, but this gun will be original iron sights - for now. In order to get her to sight in, I used a drift pin and a ball peen hammer to slide the front sight over quite a bit - noticeably off-center, and I moved the the back sight, the opposite way, a 'smidge.

I ran out of ammo to test at 100 yards. So I did only 50 yards. I was able to get a 4-5 shot grouping within 1" of the bull. I used Winchester BRI rifled slug ( a SABOT ) 2 3/4" ( gun won't accept 3" )

Questions:

Is that a decent shot grouping ? What should I expect ?
Why did I need to move the front, dovetail sight over as much as I did to get accurate ?

Thanks

[Scorpion8]

Your grouping sounds fine. Minute-of-deer kill zone certainly. It might be that you're trying to make too many adjustments at once on your sights.

[Chilly]

How are you resting the gun when shooting for groups? Sometimes the way the gun is supported can impact how it "jumps". When you are satisfied with sight settings shoot a few more offhand, or however you figure on supporting it when you light the wick on a deer. Conform your zero didnt change when your rest changed.

Also, 870 triggers arent benchrest quality. Trigger control can affect groups. A lot. Let another good shooter try a few rounds.

I had an M1 carbine and 1903A3 that required sights to be far to one side. Drove me nuts but thats just how it is sometimes.