Bull Barrel 10/22
I know this thread is a little old but thought I would toss in my 2c.
I built a couple of these 10/22's into target shooters as well. The one I built for my son has a green mountain stainless bull 18", Fajen stock, Timney trigger, Bushnell Elite 3200 6-12x scope. The barrel was very tight into the stock receiver and is free floated. I really like the Fajen thumbhole stock since it has adjustments for cheek and pull length. I also have a bull 20" installed in another one but have had scope issues with it and never got through a full match with it before the crosshairs jumped. That's a bushnell 4200 8-24x that needs a trip back to the factory.
The Timney was a great addition but the biggest change was from the ammo. I eventually settled on Wolf match ammo. Best I have shot at 22 benchrest is 21x-249 and I've also shot more than a few 20x-250's. Benchrest at my club is indoors at 15 yards. That might not seem like very long but remember the X is about 1/4 the size of a gnat - it's the size of the period at the end of this sentence. And the 10 ring is the size of the 22 round. I've shot the rifle at the 50 yard line too and I can use paintballs as targets at that range. A paintball is about 1/2 MOA so I would suspect with little wind this rifle would be MOA or better at 100 yards.
For those unfamiliar with indoor 22 benchrest: The score sheet is 25 individual bullseyes about 1.75" across, you have 30 minutes to engage all 25, one round per target. They're all on one large 11x17 page (or a bit larger) with a few practice 8 rings around the edges. The scoring targets are usually arranged in a 5 across by 5 down pattern. Shooting is usually from bags or a rest on a table/bench. 20X-250 means 20 x's (hit that period 20 times) and 25-10 rings were hit = 250, of course an x is automatically a 10.
When I use wolf to shoot a match I always use the same lot number for a session. With sight in, 5 to season the barrel, and then settle in, that can be almost a full box so I try to have two boxes of the same lot just in case. And I always shoot a tester when changing the 10 shot magazines.
About barrel break in - the 22 is so slow and the bullets so soft that it takes many hundreds of rounds to have any effect on the barrel. Not sure what the magic number is but it's gotta be high. This is one reason to buy the target barrels. A bit better rifling to begin with and not so long to settle them into that sweet spot. And as I've seen on other posts here, a bit tighter chamber is a must.