Re: Barrel breakin
Barrel Break-in and the use of Moly Coated Bullets
Before I begin, this post has been on many boards throughout the years and has been modified from time to time as I uncover more information, so you may have seen an older version at some time or another. What prompted me to research this subject was the fact that I destroyed a brand new Shilen Stainless Steel match barrel in less than 400 rounds shooting moly coated bullets and following some not so good advice to break the barrel in with the shoot and clean every round method.
Iíve spent a lot of time on this board, the BR board and other shooting boards listening to members and what works for them. Conclusion, what works for some, doesnít work for others. Being an engineer, when itís broke or you donít understand something you go back to specs and/or you analyze the problem or process with equipment capable of offering hard facts and not assumptions. So thatís what I did on this subject.
Do any of you know exactly what happens when you pull the trigger and your gun goes bang and the bullet goes down and out the barrel? Chances are you arenít even close and the same thing goes for barrel break-in, the use of moly coated bullets and fire-lapping a barrel. BTW, what I thought and what actually happens astounded me. I talked with 4 metallurgist and 8 barrel manufactures four of which really understood internal ballistics (Rock Creek, McMillan, Hart and Shilen), one hall of frame benchrest shooter/gun builder on the subject. These individuals have the knowledge, means and equipment to back up there claims and not just offers their opinions. From an engineering point of view, they all said and agreed to pretty much the same thing.
I also talked with some well known barrel builders who build great barrels, but in the big picture didnít know squat about what really happens when the trigger gets pulled and internal ballistics, this was scary because they build great barrels.
First, Gale McMillan was right in his statement, ďThis barrel break-in processes keep us in businessĒ!
This shoot and clean, shoot and clean every round or few rounds break-in process only damages your brand new match grade or factory barrel. Think of a car engine for a moment. Why do we use oil in the engine? To prevent metal-to-metal contact and reduce friction between two metal surfaces. A metal-to-metal contact will create friction and allow the two baring surfaces to sheer away layers metal creating rough porous surfaces which will only further the damage as time goes on. Your barrel is no different from the engine and the same results will happen if you clean so well you take it back down to a bare steel surface.
Mike Rock at Rock Creek barrels and Speedy Gonzales of SSG guns gave me the most detailed explanations on barrels and ballistics. Mike has his degree in metallurgy; he was also the chief ballistics engineer for the Army for many years at the Aberdeen Proving grounds. Also Stan Rivenbark was one of the top ballistic engineers for Raytheon before he retired in the late 70ís and also has a degree in metallurgy. These folks understand internal and external ballistics better than most of us ever hope to. I also talked with two local metallurgists here in North TX. I confirmed my findings with each person to see if they agreed or disagreed. Conclusion, they all agreed with each otherís assessments.
When Mike worked at Aberdeen proving grounds, the Army used high speed bore videos with mirrors, thermal imaging and computers to analyze any and everything that happens when the firing pin hits the primer and the round goes off. BTW this is the part where what you thought happens meets what really happens when you pull the trigger. When the primer ignites there is enough pressure to move the bullet forward into the lands. The bullet then stops. As the primer ignites the powder, more pressure builds moving the bullet forward where it can stop again. Once there is enough pressure from the round going off, the bullet is moved down out the barrel. All of this happens in nanoseconds (billionths of a second). Your bullet actually starts and stops at least twice and sometimes three times before it leaves the barrel. This is a proven fact.
If you clean every round or every few rounds during your barrel break-in process or clean your rifle so well after shooting that you take it down to the bare metal, youíve created a metal-to-metal contact surface for the next time you shoot the gun. So whatís the problem with this you ask? Just like your car engine, metal-to-metal contact will create friction and sheer away layers of metal from each surface. So if your bullet is starting and stopping two or three times as it leaves the barrel, thatís two or three places for metal-to-metal contact to happen as well as the rest of your bore.
According to Mike Rock and the other barrel manufactures agreed, all you need to avoid this metal-to-metal contact is a good burnish in the barrel. A good burnish in the barrel will eliminate any metal-to-metal contact, thus preventing premature damage to a barrel. More on this later. The use of JBís and Flitz and products such as those can and will clean so well that it will take you down to a bare metal-to-metal contact for the next time you pull the trigger. For all intents and purposes, JBís and Flitz type products are not the most ideal products for cleaning your rifle, but they do serve a purpose and have there place when needed.
Yes, I know what some of you are thinking, copper is a very soft gilding metal howís it possible for it to damage a steel barrel. Just as water is now used to cut steel, add enough pressure and water cuts through steel like a hot knife through butter. Add 50,000 + PSIís of pressure from your round going off and that those soft copper jacketed bullets can easily sheer layers of steel out of your barrel with a metal-to-metal contact, easily damaging and creating more rough spots in your barrel for fouling to occur.
Rough spots in barrels will easily sheer away and collect copper fouling. Depending on the severity and how rough that spot is, it may be smoothed out over time by shooting a lot of rounds, or it may need to be lapped out. This is the problem faced with factory barrels as they may have some rough spots to start out with from the machining process. Most match grade barrels are hand-lapped and most if not all rough spots and machining marks have been removed. A lot of barrels foul like hell and still shoot great, probably not benchrest accurate, but a lot will shoot in the under a 1 MOA or even .5 moa or better. So the real question is what the hell is cleaning every round or every other round going to do to improve this? Nothing, but give you a new bare metal-to-metal contact surface to start with again and a lot of wasted time and effort.
A lot of barrel manufactures such as Rock Creek, Hart and Shilen at the time of this original writing will all void your barrel warranty if you shoot moly bullets and for good reason. This is not to say that moly is necessarily bad for a barrel, but it is when applied to bullets. There is no way possible to coat a bore with moly bullets.
The bullet contact surface in the barrel is only so big. It's like trying to wax your entire car with just a tinny dab of wax and starting over at the exact same place each time you apply more wax to applicator. You just can't cover the entire car, but you get a nice wax build up at the starting point. Same thing with shooting moly coated bullets. You get a nice moly build up right in the throat area and not much moly beyond that.
When your round goes off, moly comes off the contact surface of the bullet in the throat area of the rifle and is bonded to the barrel do to the excessive heat and pressure. Were not talking coated or adhered to, weíre talking bonded to. In addition, add carbon fouling and some of the copper jacket from the bullet to the mix. Follow this up with another round and youíve now embedded the carbon fouling and copper jacket between layers of bonded moly. This is the beginning of the black moly ring, which ruins countless barrels and is so hard; it can hardly be scraped off with a screwdrivers corner edge. This is what happened to a brand new Shilen SS select match barrel I had to have replaced with less than 400 rounds through it. I was shocked when I looked through Speedy Gonzalezís $3000.00 video borescope at the damage to my new Shilen SS select match barrel. Speedy wasnít amazed at all, he sees it day in and day out with barrels that have less than 50 rounds of moly coated bullets through them.
For those of you who think youíll clean the black moly ring out of your barrel with a solvent, youíre kidding yourself. Name one gun cleaning solvent that will dissolve Molybdenum Disulfide (MoS2). Youíre not going to find one. I understand some cleaning products will remove loose moly from the barrel, but Iím unaware of any product that will dissolve bonded on Molybdenum Disulfide from a barrel and not destroy the barrel steel in the process. Some moly users say they brush it out when they clean their rifles. Without looking through a borescope, how would you know? Doug Shilen at Shilen barrels cut the throat section out of my ruined barrel to see the specific damage once he determined it was toast. He could barely scrape the black moly ring out with the sharp edge of a screwdriver on the barrel I ruined. I could have scrubbed with a bronze brush for days on end and I wouldnít have touched it.
Fire-lapping is one way of removing rough spots and smoothing out a barrel, if you canít have your barrel hand lapped. But just like using moly coated bullets, lapping compound coated bullets have there own built in problems. As with moly coated bullets, the bullet contact surface to the barrel is very small. Most of the lapping compound on the bullets will be focused in the throat area. Your throat will get a great polish job, but you might lengthen the throat the in the process, but it can help to remove rough spots in barrels.
When I talked to Mike Rock about my new barrel and the barrel break-in process, this is what he had to say. He first hand laps each barrel with a lead lap. He then uses two products from Sentry Solutions, a product called Smooth Coat, which is an alcohol and moly based product. He applies wet patches of Smooth Coats until the bore is good and saturated and lets it sit until the alcohol evaporates. The barrel now has loose moly in it. Next he uses a product called BP-2000, which is a very fine moly powder. Applied to a patch wrapped around a bore brush, he makes a hundred passes or so through the barrel very rapidly before having to rest. He repeats this process with fresh patches containing the moly powder a few more times. What he is doing is burnishing the barrel surface with moly and filling in any fine micro lines left by the hand lapping. He then uses a couple of clean patches to knock out any remaining moly left in the bore.
With the barrel burnished with moly, this will prevent any metal-to-metal contact during the barrel break in process. My instructions for barrel break-in were quite simple. Shoot 20 rounds (non-moly bullets) with no cleaning, as this will further burnish the barrel. Done! Now shoot and clean using your regular regiment of cleaning and if you have to use JBís or flitz type products, go very easy with them, or better yet avoid them. Never clean down to bare metal.
He said most of the cleaning products do a great job, donít be afraid to use a brush and go easy on the ammonia-based products for removing copper fouling. Basically donít let the ammonia-based products remain in the barrel for long lengths of time.
Well thatís the long a skinny from the engineering point of view on the subject. If you're ever in doubt about the real condition of your barrel, take it someone who has a bore scope and even better if someone has a bore scope that can magnify the view. You may be surprised at what is really going on in your barrel.
I'm sure this will spark a debate here and there, but that's good thing. The more information we have, the better off we'll be.
Distance is not an issue, but the wind will make it interesting!