Home Forums Hunting & Shooting Ask The Gunwriters Barrel Break-in

Yup, that's my rationale, too.

I believe it was an article in American Rifleman. It was only several years back. Last time our cousins got together for a Prairie Dog hunt I brought the subject up. That was three years ago. Sadly this hunt used to be annual. But we're doing again in two weeks. 😊

As I recall the author was a clean fanatic, cleaning after every ten rounds or so. If I recall correctly at least some of but not all was in regards to Ar-15's, M1's and the like. But he also covered bolt action rifles. He may have even brought up bench rifles.

It's not that I'm not a cleanliness freak, it's that I have other things to do. And oh yes, to have complete disclosure both my wives (past and present) think/thought that I'm a slob. But they obviously have/had judgement issues.

The article was news to me and I've not seen another, pro or con.

Guess we gotta double team JB from time to time...

He's a purist, I'm more along the lines of expediency, if a little is good a lot must be better...

DF

Actually, NOT installing DBC in every barrel is all about expediency for me. If I installed DBC in every rifle that came in the door, I wouldn't get much else done. If only one rifle a month showed up it would make sense, but that's not the way it works around here!

So I install it in some to forestall almost certain severe fouling, and decide on the others after shooting them.

JB's day job is to fool with rifles, as where I don't have time to sort out which barrels need help and which don't, so while I didn't always do it this way, now they all get treated right out the gate since I've never seen DBC be detrimental to any barrel yet, so I figure it can't hurt. It doesn't take me long to get brand new barrels clean to bare steel, and I would be running a couple of patches down anyway to clean up any metal shavings, and applying the coating takes an extra 5 minutes.

I'm sure JB doesn't mind us having diverging thoughts when it comes to a preference issue. Now if this was a technical disagreement we'd be in trouble

Ha!

Yeah, I'm at the range quite a bit (last week three times), so it doesn't take long to sort them out.

I've also never seen any negative effects from DBC, and in fact one other reason I sometimes install it is rust prevention. Rifles normally don't rust much here in Montana, but while I don't travel to hunt as much as much as a few years ago, once in a while I end up someplace wet. Which is why my rifles with waterproof exteriors tend to have DBC'd bores as well.

Agreed. It's pretty dry here in AB, too, but I like not having to worry about rust at all, so my rifles either have Cerakote or DGS on the outside and DBC on the inside. I've seen some simply amazing things when it comes to DBC preventing rust.

I see JB's point; it's not a technical issue, a function of logistics.

Makes perfect sense. (Not surprising... )

I don't have that many; it's easy for me to DBC them all.

DF

My "opinion" is the only breaking in of a good custom lapped barrel is the throat. To alleviate this I put a bronze brush in my electric drill, wrap the brush with a little 0000 steel wool and lap the chambering fluff out of the throat. About 5-10 seconds. The bore has been lapped already and the machining fluff from the reamer in the throat is your problem. Now, just go out and shoot it. I don't use factory barrels and would not form any opinion on them.

Taking this to the next logical step (uh-oh ) is there a consequent drop in pressure/speed after application which allows a higher charge to attain the same pressure/speed?

Or is that just crazy talk?

I think that rather than "allowing" a higher charge to achieve the same pressure/speed, it would be "requiring". Using more powder to achieve the same thing wouldn't seem to be a positive to me.

yep yep

That's the point of my question, I guess.

Does that occur and is it a significant difference - fouling aside.

Velocity of the bullet comes from sustained pressure as the bullet is pushed down the bore (bear with me). There are two primary sources of this pressure that is generated- the inertia of the bullet and the tight fit between the bore and bullet, providing resistance against the rapidly expanding, hot gases in the chamber, as well as the coefficient of friction between the bullet and the bore. The bullet's inertia and bullet/bore fit is by far the biggest contributor to resistance, and therefore pressure generation, with coeff. of friction between the bullet and bore being a very minor portion. An analogy would be you trying to push a 10,000 lbs boulder through a doorway in your living room (don't ask me how it got there) on carpet versus linoleum. The difference in resistance the boulder gives you when pushed on carpet versus linoleum is pretty insignificant, considering the amount of force required to overcome the inertia of the boulder and squeeze it through the doorway. This can be seen when we modify the friction between the bullet and the bore by either changing the bullet material or the bore surface. In this case, the coating fills in pores and reduces friction, but the change in overall pressure is minimal.

But the reduction in the coefficient of friction is enough to prevent the bullet's jacket from scraping off and being deposited in the pores and crevices of the bore.

Here's a couple of 1000 words to show you what I mean: