running in barrels.

[bruce moulds]

for quite some time i have believed that running in barrels was best done with light charges, allowing the projectiles to burnish the leade (freebore) with minimal interference from powder gases.
running one in recently using a borescope has altered this view.
the new chambr showed the usual tool marks across the axis of the bore. these are what we want to burnish.
running in removed them bit by bit as expected.
while bullets might have been burnishig them off, but i now suspect it was flame melting them off. after about 60 shots, the area was dead smooth, and i don't think something as soft as bullet jackets can remove steel at that rate.possibly there is some abrasive action of powder fouling as well when you go to 2 and more shots.
there is also no question that a barrel keeps running in for up to 200 shots. not sure what goes on here.
i do believe running in is beneficial to accuracy.
bruce.

[IanP]

If I'm fire-forming cases I will run in with lighter loads as experience has taught me that full loads can result in split case necks. Otherwise I use full competition loads to run the barrel in.

A little story to illustrate...

I made a big mistake running in my 22BR! I got the load data from the usual places on the internet and loaded up some cases with 80gr Amax, (to run barrel in) and some 90gr Berger VLDs to chrono and check initial accuracy.

I put the first 80gr Amax in the chamber and fired it down range at 3260fps, wow I wasn't expecting that! I had great difficulty opening the bolt of my Barnard action attached to a 31", 7.8T, 1.25", new Krieger barrel. I had driven to Para Range to run the barrel in and I wasn't going to let tight bolt lift stop me.

I shot 9 more 80gr Amax bullets down the tube and cleaned vigorously between shots. Bolt lift was tight for all shots fired and the copper kept coming out on the patches. I then changed over to the 90gr Bergers (same powder charge) and discovered incredible accuracy and no more tight bolt lift. I was shooting 3 shot groups at 100m targets and settled on a load that managed to put 3 bullets thru one hole.

Over time I discovered a tight spot just in from the muzzle end when cleaning the barrel I worked on it with some JB paste. The initial loads had obviously been well over what was needed and had left copper in the barrel. The tight spot cleaned out ok and this rifle is one of the most accurate that I have in my possession.

What I learned from this experience is not to put too much faith in internet data as chambers differ considerably. I also discovered that hot loads dont damage barrels if used to run them in, although continued use would certainly shorten barrel life. I also discovered JB paste works well in getting the last bit of copper out if its been allowed to build up a little over time.

My method these days is to check a recommended load in my chamber before loading up too many all the same to perform the barrel run in. I now use JB paste to clean the first few shots (after cleaning out the powder residue with Butch's Boreshine) to polish the throat.

I have quite a few barrels and they have all been run in with (tested) match loads and so far they have all cleaned up pretty well, (zero copper) after 20 shots. I agree with Bruce, about 200 shots needing to be fired before optimum accuracy is achieved.

The reality of barrel run in is that shooters use all sorts of methods and most seem to work, but for me I use match loads and check velocity and accuracy and all my accurate barrels are that way after the first 10 to 20 shots are fired. Dont waste your barrel life thru excessive run in, would be my advice.

PS I eventually got a borescope and can now check to see if my barrel is clean. It really hasn't made any difference to my run-in procedure as what I was doing worked.

Ian

[Woody_rod]

Its not really burnishing, its just erosion. The more you shoot from the first round, the more wear and erosion will occur.