Barrel Break-In

Break-in vs Chrome bore

Hi,

I used to be the quality manager for cut rifle high end barrel making outfit and am very familiar with the wide and varied opinions and processes for barrel break in - I won't try and tell you whats righ and what's wrong (there is a lot of dissagreement by even the best informed people).

But consider this for what it is worth:

High end stainless and chromoly barrels (really high end) are lapped (pollished) by hand with lead slug cast inside each barrel and coated with a fine abrassive. When you start lapping it feals irregular (tight spots and rough spots) and then slowly gets better until you can 'bump the slug" (block the end of the barrel and ram the lead slug into the end to increase its size slight - you do this several time while lapping) and the enlarged lap while tighter will feel smooth and drag free from one end to the other.

A barrel like this will last a few thousand round depeending on caliber and maintanence (care and feeding). A chrome barrel (like on the P90) will last tens of thousands of rounds and will show virtualy know wear only acknoledging severe abuse for thousands of rounds. These barrels are expensive judged harshly on the degre of sub MOA accuracy the achive and can maintain and are discarded at the first sign of degredation. A few rounds and an hour of ones time the first time at the range seems a small price to pay to the alter of extreme accuracy and one hole bragging rights.

Chroming a barrels smooths over some of the manufacturing imperfections but the rest our captured and preserved for the very long life of that barrels.

I highly recomend if you have high end custom barrel to call the manufacturer for their recomendations and enjoy going through a little extra grief in the interest of making the most of your investment. I say call the barrel manufacture in question because each shop is different and may lap at different times and in different way with different compounds. We lapped after drilling, after reaming and after rifling but we specialized in accuracy test barrells for R&D.

Hope that is in some way useful you have made my lapping arm sore just thinking about those days...

TB