Is there a general rule regarding bullet/ammo choice for breaking a barrel in? I know the whole break in thing can be debated, but it certainly doesn't hurt. What I'm wondering is whether is considered ideal to use a mild load to break in or to use a Heavy bullet at reasonable velocities. Also, any comments on starting a fresh barrel on Moly coated bullets?

I would use whatever bullet and load you want to shoot with. I don't think that the bullet matters as long as the barrel is kept clean until the bore smooths out. Whether break in is beneficial, I couldn't honestly tell you for sure. I broke in my Rugers barrel and it shoots great, but I have no way of knowing how it would have shot had I not broke it in. I do think that you are right about most break in proceedures being harmless, whether they offer a positive benefit or not, they won't hurt anything either. It's my opinion that factory production grade bores may benefit slightly from a break in proceedure, but I highly doubt that a rigorous break in would have any effect on a match grade barrel that has been completely stress relieved, hand-lapped and polished to a mirror smooth finish.

As far as using moly (molybdenum disulfide) coated bullets, from the research I've done I've decided that I would never use them in a rifle belonging to me. In order to properly treat a barrel with moly it needs to be done with a spray-on or bake on process that evenly plates the bore, and then you are committed to using only moly coated bullets. Once applied, moly is very hard to remove. If you choose to use moly coated bullets in an untreated bore, you wind up with a bore that is very unevenly treated, with a heavy coat of moly near the throat and little to no moly toward the muzzle because the moly rubs off before the bullet gets there. This means inconsistant bore diameter with the bore effectively getting bigger toward the muzzle, which is a highly undesirable condition.

A small percentage of shooters swear by moly, but I for one won't use it. If you take care of your bore then copper fouling shouldn't be too troublesome. And I'd gladly sacrifice maybe 100fps to not have to go through the trouble to apply and maintain a moly coated bore.

Mike

Thanks Mike.

As for the Moly bullets...I had found some of the same overtones in my own research. I was lead to believe if you started with moly (so that your hard-to-remove moly was the base layer or fouling)you would be fine. I had not considered the changing bore diameter. I too will stay away from them...and wish all the more I'd never used them in my 22-250 (only 40) I've not notice anything bad yet, hopefully I stopped soon enough! Youthfull ignorance really sucks sometimes

When I break-in a firearm, I use the heaviest bullet for that caliber I can find due to greater bullet to barrel bearing surface. I use a medium load about three steps below max. I will usually use Hornady Innerlock Bullets. I don't now if it makes any difference in the break-in procedure its just what I do. Good luck.

Usually, I use the cheapest bullets I can find. And usually factory ammo. Seriously. One, when its a new chambering, I get very excited and want to get out quick as possible to break in. Two, I just won't put the time into reloading if not serious load development or serious hunting/target ammo. I have a hard time finding time to wipe myself these days.

But in reality, it would be best to break in with the bullet you plan on using. that way you can get an idea of how they will shoot. It will usually show some potenial or not at this point. If you plan on shooting A-Frames, I understand buying some corelokts to do the break in. I have to take out a second morgage for them myself.