Finally ready to sight in my new CZ527 American in .204, after the help you guys provided me with caliber selection. Should I run the bore with bore paste and then clean thorougly prior to shooting? or just go ahead and shoot and then clean it afterwards? Thanks.

uplandr, I don't think I would "bore paste" that new barrel! Clean it with Hoppes prior to shooting and if you want to follow a barrel break in procedure, Clean with Hoppes and Sweets after each of 5 shots, then go to 3 shot strings and clean and after 5-6 of the 3 shot strings you can go to 5 shot strings and clean. You should notice the amount of copper fouling getting to be less and less and once you get it to the point where the copper is negligble after the 3 or 5 shot strings, go ahead and shoot as you would any of your other rifles. There are some who say barrel break in is voo doo. That's fine! I don't beleive in voodoo but I do beleive in barrel break in! Will it improve accurracy? Probably not but what it will do is allow you more shots before accurracy falls off for the life of the barrel! GHD

I'm with Varmint Al on break in, cept for the moly bullets. Works for me.
http://www.varmintal.com/ashot.htm#Break

Hey uplander. My breakin is different from GHD's, I use the one posted by Dan Lilga. There is probably no topic on this site that will bring on a wider spread of opinions, but here's mine.
I would indeed clean throughly before firing, you'll be amazed at what all comes out of the bore before firing. I use Shooters Choice, JB Bore Paste, bronze brushes, Sweets, rubbing alchol and of course lots of patches. That's the stuff I use, here's the procedure.

First, don't mix harsh chemicals. That's why I use alchol between em to neutralize one bfore using the next, with the exception of JB's which I use with the others. Sweets and Shooters Choice mixed have been reported to etch barrels, never seen it don't want to.
Here we go.
A number of wet patches of Shooters Choice followed by the bronze brush, wet SC patches again till clean then let it soak for 15minutes. Now take a snug patch and coat it with JB's and short stroke it up and down the barrel 10 or 15 times, wet SC patches till clean then dry. Now this part is important, if you shoot a bullet down a completely dry barrel the minute rough spots in the bore want to tear copper from the jacket and foul the rifling. By shooting and cleaning one round at a time your going to smooth or lap the rough spots before they get a chance to fill up with copper and cause cleaning problems for the life of the barrel.
Now back to the clean dry bore, wet one patch with Shooters Choice and run it down the bore followed by one only dry patch, fire one round.
Now clean again with wet patchs SC brush another lighter go round with JB's dry and the run a patch of alchol down the bore to neutralize the Shooters choice, then dry. Now use patches with sweets and soak with sweets (no longer than 20 minutes) until there is no blue. You are now back to bare metal, dry patch, use the alchol to neutralize the sweets, dry patch again then one patch of SC one dry patch and fire. Do it again.

That's the process, Lilga says do it 10 times. Somewhere around the 7th or 8th round you'll notice that when you use the sweets it doesn't turn blue anymore. Mission accomplished!
Now shoot three and clean to bare metal for about 30 rounds rounds always remembering to one patch wet and one only dry before shooting the first round.

As your undoubtdedly thinking, "Yes this is a pain in the ass"! But I promise if you do it right you'll have one of the easiest cleaning low maintainence barrels you've ever had.
Lilga, Pac-Nor all of em use some version similar to this for breakin, I find it especially important on factory barrels which aren't lapped as smooth as the customs. CZ does a better job than most smoothing them up but too me proper break in is more than worth a nasty day of breakin.
What you've done is to bullet lap the barrel and removed the little rough spots before they fill up with copper, once they do it's too late.
I use JB's and have for years, don't over use it but you will find it a big help in the breakin process and on occasion later after long strings on a p-dog town. That's what works for me, good luck.