View Full Version : Break in new barrel with moly

February 27, 1999, 03:20 PM
Is anyone familar with the steps to breaking in a new rifle barrel with molybdenum disulfide?

March 17, 1999, 10:26 PM
This is how I do it, there are other ways.
Clean your bore thoroughly. (I'm assuming you're familiar with stuff like bore guides, Shooter's Choice/Kroil, JB compound, etc.) This includes a scrub with solvent and brush. Dry, and using an undersize brush/boremop&patch/or wrapped patch that's fairly snug, scrub some more with JB. About 25 back'n'forth. Wetpatch again a few times, and dry. Fire one round, clean thoroughly, for 10 rounds, then fire three and clean for 30 rounds. If you have a factory barrel, go to 5 shots and clean until you have 100 total. That should break it in. After breakin, use Midway's Molybore Prep after cleaning (flush bore with lighter fluid on a couple patches to get the oils out after cleaning...) then wet patch the MBP through with short strokes. Give it a few minutes, and run 2 dry patches through to get the excess out before firing. Hope this is of help.

Shoot carefully, swifter...

Jeff Thomas
March 18, 1999, 02:37 AM
Swifter, I respect your experience, but I honestly get more confused about this issue than almost any other.

For example, on Bushmaster's web site, they discuss breaking in their chrome-lined AR barrels. The essence of their advice, as I recall, is to not excessively clean before you've put 200 rounds through the barrel. Others will say they just start shooting, and forget the age of the gun. Then I read posts like yours, which makes the whole process sound much, much more complicated.

What is the scientific truth and logic for breaking in a barrel with molybdenum disulfide? And, why does barrel break-in seem to generate such fervent and varied responses? Does / should it vary with barrel material, twist, etc?

Honestly somewhat perplexed. With the investments required in fine firearms, this seems a very important topic to me.

March 18, 1999, 12:15 PM
The complete answer requires a lot better typing skills than I have, 'cause its long. I'll refer you to Precision Shooting magazine, they have had most of the info I use.
To make it short, basically, the two schools of thought are: 1) Use non-moly'd bullets, they will help remove the microscopic burrs in a new barrel better; and 2) Break it in with what you plan to shoot, those are less burrs than microscopic scratches, better to fill them with moly than gilding metal.
Break-in, generally, is a process of starting with a clean barrel, and keeping it clean for the first series of shots. Almost invariably, a custom barrel will show signs of being broken in in a very few shots (10-20), while a factory bore will need many more. This is almost certainly due to the custom having been handlapped, and given greater attention.
"Just shooting" the rifle means, to me, that you will put one layer of fouling on top of another...
Finally, the rifles that I've broken in properly are much easier to clean than the others. And don't lose sight of the fact that this technique was developed by shooters to whom a 1MOA group is not a triumph, but a disaster!{;0))

March 18, 1999, 11:56 PM
Had a random thought - or a senior moment...
If you are interested in moly, and in the science, etc., try: www.xtremeaccuracy.com/
They have a large amount of data. :D

Shoot carefully, swifter...

Jeff Thomas
March 19, 1999, 01:50 PM
swifter, thanks for your help. And, I like that 'senior moment' comment. ;)

xtremeaccuracy.com looks interesting, and I'll check out Precision Shooting magazine as well. [BTW, do you have any contact info on Precision Shooting?]

Have a good weekend.

Dennis Glover
March 19, 1999, 08:48 PM
What is the real truth about moly'd and stainless steel. Seems there may be a problem when shooting moy'd bullets in these barrels.
One of the hand gun barrel makers report excessive wear after testing 3 of their barrels with bullets coated with moly'd. I think the barrel maker was scheman or some thing like that it is at their web site.

March 20, 1999, 12:30 AM
Jeff, I can't seem to turn up the web address of Precision Shooting, I know the had one at one time... Phone Number is: 860-645-8776. Mail: 222McKee St./Manchester, CT, 06040. You also might check out : www.benchrest.com/, might be a link to PS over there. Lots of data, anyway :)

Shoot carefully, swifter...