Went shooting today to test the Marlin with the "lapped" barrel. Swabbed the bore last night and looked at the bore and it looked exactly the same. I'm a machinist, I know that lapping can't clean up the chatter in the bore, so I'm probably going to call Marlin again and give them an ultimatum: either put a new barrel on this gun or give me a refund.
I shot with the irons today at 25 yards, using the same setup I did last time. I didn't have time to buy sandbags, but I am going to be buying a Caldwell Matrix rest in the next week or two and I'm going to try again after I get it. Also, I'm going to put the scope back on the Marlin and see if shooting with it will help me.
Idk what it is, but I'm just able to shoot the Mossberg better. It could be that the front sight on the Marlin is so far away and just too small and hard to see and I can't get a good picture, so I figure a scope at 25 yards won't hurt.
I started shooting at 15 yards and the Marlin seemed to be doing really well, but it seemed that the more I shot it, the bigger the groups were getting even after letting the barrel cool. I'm thinking it's possible the microgroove's may be so shallow that they foul quickly and degrade accuracy after 50 rounds or so.
Here are some pics. I shot these groups at 25 yards. I tried to do 5 shot groups, but I was loosing light at the end of the day and had trouble making out some of the hits, thought I missed, and took a 6th shot at times. I labled the targets with the rifle and the ammo used. The only supersonic or high velocity load I used was the Winchester White Box the rest was either standard velocity or subsonic ammo.
As you can see the Aguila Sniper Sub Sonic shoots really well out of the Mossberg and crap out of the Marlin. That's okay, SSS is a weird round. Winchester White Box shot okay out of the Marlin, but better from the Mossberg. Same with CCI Subsonic.
Again, the Mossberg just keeps beating the Marlin.
Take a look, take a lookers: