Ammo to use for Breaking In a New Rifle Barrel

Hey Folks,

Just picked up a new .308 rifle, and the instructions give a 100-200 rnd break in procedure. They also recommend Moly Coated rounds for the break in period.

Does the moly really matter? Can I use any available ammo? I would guess that it wouldn't matter due to the cleaning in between shots, but I am not an expert on this topic.

Any help on this would be greatly appreciated.

Thanks,

Q

Anything unusual about it? Make and model? Stainless barrel, strange composite material? I dont know the answer,but it may help someone who does.

Armalite AR-10T

http://www.cabelas.com/cabelas/en/t.../search-box.jsp.form23&_dyncharset=ISO-8859-1

Saw this the other day. Haven't tried it personally, I never knew it existed.

They have reloading supplies also with the same type bullets if you roll your own.

guthook said:

http://www.cabelas.com/cabelas/en/t.../search-box.jsp.form23&_dyncharset=ISO-8859-1

Saw this the other day. Haven't tried it personally, I never knew it existed.

They have reloading supplies also with the same type bullets if you roll your own.

Click to expand...

midway or brownells may have them cheaper than cabelas if you check.

im planning on loading some up one day and shooting a few through my browning A bolt in 7mm rem mag.

I'll have to get a new gun just to try 'em out

The idea behind molycoated bullets is that they leave a thin film of moly inside the barrel that acts as a lubricant to reduce friction, and therefore heat, pressure and fouling are reduced. The benefit being that consistency is maintained after more rounds are fired than with uncoated barrels. Cleaning with something like wipeout will remove the coating, so you have to shoot moly bullets every now and then even after the break in period to maintain the benefits. I tried comparing 10 consecutive 10 shot groups out of my savage 10FP in 308 after being cleaned with wipeout, and sending 20 coated bullets through, boresnaking it and then starting the uncoated strings without cleaning in between, then trying the same with 20 uncoated bullets, boresnaking, and then the 10 strings without cleaning, and then 10 strings while running the boresnake through once in between every 10 shot string. I shot each 100 or 120 round set on different days up at Hap Baker at 200 yards, and basically only counted the 8 best shots of each group, and used the same loads for all, 168gr Nosler HPBT match over 45.5gr of varget with a CCI LR BR primer in fireformed winchester cases, and allowing about 10 minutes in between 10rd groups to let the barrel cool, the wind and temp on all 3 days was about the same, and I shot all rounds from noon to about 4, with the moly coated set fired last. I found the first string of the third group to be the least accurate, basically 10 rounds through a clean, cold bore. There was little diference for groups 2 through 5 across the 3 sets, but from 50 rounds on out the uncoated barrel that wasn't cleaned started to produce incrementally larger groups than the other 2, and by the last string the moly coated bore seemed to have a hair bit better accuracy than the one getting boresnaked every 10 rounds, of course the difference was only about .25" at 200 yards on the 9th group and less than that on the 10th group, both groups were between 2" and 2.5" for just about all the strings except the first, the uncleaned untreated groups ended up spreading out slowly to a little more than 3". Of course this was not a perfect test, there were a lot of variables , lighting, bench position, and while wind and temp were close, they were not exact, and I was shooting off of a bipod, not a fixed benchrest or anything, but the results were about what I expected, moly works, but outside of bench rest competition firing a ton of rounds, it doesn't make much of a difference to those who clean the barrel well after a day shooting 50 rounds, and in a chrome lined barrel, I doubt there would be a difference at all.


I would be interested to see what E.shell has to say about them, he is the go to guy for stuff like this, I'm a tinkerer, he is a expert

barrel break in is a myth

guthook said:

http://www.cabelas.com/cabelas/en/t.../search-box.jsp.form23&_dyncharset=ISO-8859-1

Saw this the other day. Haven't tried it personally, I never knew it existed.

They have reloading supplies also with the same type bullets if you roll your own.

Click to expand...

David Tubb's Final Finish system adds several hundred rounds wear to the throat in just a few shots. While it can fill a niche, IMO it is too aggressive for use with a good quality custom barrel. It can be a potential help for a rough factory barrel that fouls badly and/or delivers mediocre performance, and I know of a few shooters that have used it to reduce fouling, although immediate accuracy was unaffected. You can't get something for nothing, and when the abrasive removes material, the mechanism is much like extra shots, and barrel life will necessarily be affected.

David Tubb is a uniquely talented shooter, head and shoulders above most of his contemporaries, but he is also very much into exploiting his shooting prowess to market various merchandise, some of which are, in my opinion, gimmicks. David's talent could dominate the national matches with a Red Ryder BB gun, and if he thought he could make money at it, he'd endorse them as the ultimate match guns based on his performance with one and sell them like hotcakes.

David's custom 6mm Sierra MatchKings, the 115 DTAC and newer 111 DTAC, are great ideas and I use the 115s, but, were we talking about my own AR-10T and it's hand lapped bore, I'd not let those Final Finish bullets near it.

Mdman said:

barrel break in is a myth

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Interesting that you'd be so certain, when even well known experts (barrel makers, precision gunsmiths and world-class shooters) still disagree. How did you arrive at this final conclusion?

IMHO, it IS of limited value and may indeed represent wasted ammo, effort and barrel life.

The theory is that each passing bullet will burnish and slightly smooth rough spots, and cleaning between bullets is necessary to prevent a copper deposit from shielding the rough area from successive bullets. A build-up of copper fouling is often detrimental to accuracy, since minor deformation of bullets occurs as they force their way past the dimensional change the buildup represents.

How much value this break-in process really has, and just how well this works is very much debated, but is has been shown that new barrels often copper foul more severely until they have had some rounds through them.

With a top quality custom barrel, there is very little roughness that can be addressed with a jacketed bullet. These extremely uniform and often hand lapped barrels are typically so smooth, there is little copper fouling even from the onset of shooting.

With a typical factory barrel, there is no amount of bullets going by that will remove the tool marks so commonly seen, and a rifle with a rough bore often shoots better once a little fouling accumulates.

I think that IF one derives any benefit at all from going through the tedious "shoot one/clean, shoot one/clean . . . " break-in process, it will be with a mid-grade custom barrel.

My last few custom barrels, a Broughton, a Bartlein and a Schneider, barely fouled at first, and cleaned up very quickly and easily. I did not bother with the full-blown break in process and it was only a few cleanings before they all nearly stopped copper fouling completely. The last two custom barrels before that were Harts, and I did go through the break in process and they fouled a little at first, but it abated pretty quickly and with relaitvely few rounds fired. All in all, I'd bet the number of rounds was the only difference and the number of cleanings were the entire similarity.

My last two factory barrels were both Remington, an LTR and a VS. The LTR was new, the VS was used. My borescope showed a tremendous amount of roughness in both bores, mostly radial tool marks on the lands, but also radial marks in the grooves, as well as lateral gouges. The LTR didn't seem to care whether it was clean or dirty, and in spite of it's very rough bore, it shoots extremely well, keeping FGMM 168s within 3/8 moa. I keep this rifle clean, and go over it after every shooting session. The VS never truly shot well, and seemed to shoot better with longer periods of shooting between cleanings. I stopped cleaning it - why bother? I eventually changed the barrel out to an ER Shaw short-chambered barrel which I finished with a PTG Palma 95 reamer. The bore on this one was rough as well, and I tried the prescribed break-in process, but it didn't seem to accomplish anything, as the barrel still fouls considerably and is only marginally smoother than the OEM tubes, although accuracy is much improved. I only have a hundred or so through it so far and wonder if/when fouling will abate.

I think that, if anything can be attributed to the process, the amount of fouling reduction in a good barrel is more tied to the number of firing/cleaning cycles than to the actual process by which the first rounds are fired. If you clean after every shot, you'll get a lot of cleaning done pretty quickly. If you shoot a box of ammo through it, then clean it and then shoot another box, I believe the fouling will abate after about the same number of firing/cleaning cycles, which will take place over a longer period of time.

The AR-10T has a decent quality SS lapped barrel, which may or may not benefit from the break in, but I'd suggest not. The bore finish should already be so smooth that there is very little roughness to remove/burnish off. Were it mine, I'd clean it thoroughly, then go shoot it awhile, then clean it thoroughly and just keep it clean by a good solid cleaning regimen after each shooting session.

Alucard 0822 is right about the moly, and in the case of break-in, I'd suggest that moly isn't necessary and also prolongs any smoothing action the bullets would have. For your .308 AR-10T, with it's precision SS barrel, I really doubt you'll be able to tell much difference between coated & uncoated bullets and it will be hard to tell what the extra expense and aggravation is buying you.

Moly was a fad, a big deal highly touted by the sellers of moly coating equipment and supplies, and sellers of moly coated bullets. If one looks back now, to a man, those proclaiming the virtues of moly were all invested in it to some extent. These days, most serious shooters have come to believe that moly adds yet one more variable, one more contaminant to build up in the bore, and is even detrimental, as other fouling becomes trapped under the moly. There are even cases in which moly is said to have promoted corrosion by trapping moisture under the layers and/or promoting electrolysis.

Moly "allows" greater powder charges, but, by the same token of reduced resistance and lowered pressures, more powder must be added to regain lost velocity. It is usually possibly to slightly surpass the velocity of an uncoated bullet, but not by much.

I tried running moly in a 6.5-300 Wby, a 6.5-284 and a .223 and gave up. The best results were with the .223, due to less powder fouling keeping my cleaning frequency down enough to really benefit by the moly coating. Even at that, cleaning with enough intensity to remove carbon fouling also disrupted the moly coating and a "seasoning" time was necessary after each cleaning. Even cleaning with a mixture of Kroil and Shooter's Choice, purported to remove powder fouling while not unduly disturbing the moly, still fostered problems. My CCBS were often nowhere near the dirty group.

The 6.5-300Wby was a disaster, since the moly does nothing to reduce or prevent carbon fouling. This extremely overbore cartridge is in a tight-neck chamber and this, coupled with mass quantities of H-870, required cleaning every 20 rounds or so to prevent pressure excursions due to a hard carbon ring in the throat. After this cleaning, it took 3-5 shots to settle back in, then I had @15 good rounds before cases got sticky again.

The 6.5-284 was a little better, and I could shoot a two day 150 round tactical match w/o cleaning with only minor accuracy degradation. Then once cleaned, I had a very predictable CCBS at -1 moa, then shot #2 was -3/4 moa, then successive shots kept climbing until they were back up into the same POI as my fouled groups at shot #5. This cost me several match points, when I at first did not realize the extent of the error,, then later when I forgot to add to my come ups. 1 moa doesn't sound like much, but when your CCBS is at a 2" tile at 400 yards, it's a huge miss. Finished off that 6.5-284 barrel shooting moly for a total of 2,037 rounds, then rebarreled it and now run all uncoated bullets. My CCBS is centered in my dirty group and is one less thing to think about and/or screw up. If my barrel life is affected at all, I'll probably make that up not firing five fouling shots and trying to get out layers and layers of sandwiched fouling types. No on hates to clean a rifle more than me, and coming home with three or four precision rifles is no small matter. If moly actually helped at all, I'd use it, but, it doesn't and I don't.

Even David Tubb, once one of the most vocal early proponents of the wonders of molybdenum disulphide, has discontinued moly coating his 115 DTACs. He is now *selling* Boron Nitride (BN) as the miracle coating du`jour, and it's supposed to have all of the benefits of moly with none of the problems. We'll see. . .

I think that the single potential benefit of moly, BN and other coatings that add lubricity is the reduction of retained in-bore yaw. The coated bullet yaws as much as an uncoated bullet when throat vs bullet geometry permits, but is not forced to slump as badly in the yawed position upon encountering the rifling. The lubricity enables it to slightly straighten as it enters the throat, reducing yaw and nutation in the early stages of flight. Nutation is what one sees when they speak of certain bullets shapes needing to "go to sleep" and exhibit less accuracy at closer ranges, and this same nutation causes a degradation of ballistic coefficient during early stages of flight, when BC is most critical. With the wide selection of bullet shapes these days, it is usually possible to skip coatings and just go to another ogive shape and reduce in-bore yaw when one's throat is a little big and long.

For the added steps, mess and expense, I'll be sticking to uncoated bullets until the jury comes back in on BN, but even then I suspect I'll just continue to shoot them nekid.

I cannot rember where I read this but Gale Mcmillan talked about how barrel break in is realy about selling more barrels. about how the people who will bother with these custom high quaility barrels will notice when accuracy degrades and will buy a new barrel, and if you waste a 100 shots on a barrel with a break in procedure, on a barrel that has roughly a life of 1000 shots. you sell 10% more barrels.

that and there have been barrels that have not been broken in yet they produce 3/8 inch groups,

E. Shell and Alucard and everyone else,

Thanks for the information. I've got a bunch of surplus 146 grain .308 that I can use for pseudo break in, and some 168 grain Match Grade stuff. I think the barrel is in decent shape, and Armalite contradicts themselves in the data sheets by saying you MUST break the barrel in with the following procedure, and two pages later state that the President of the company (a competitive shooter) justs shoots and cleans which is supported by a barrel manufacturer, and E. Shell. As an engineer, I don't think that the break in would benefit the rifle much due to it being "triple lapped" already, and the amount of smoothing/lapping from the rigorous break in period with moly would be a minimal accuracy gain at best as brought up by Alucard.

I'll shoot it this weekend, and let you know what the groups look like with the pseudo break in.

Thanks again,

Q

Mdman said:

I cannot rember where I read this but Gale Mcmillan talked about how barrel break in is realy about selling more barrels. . .

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Probably here:http://www.6mmbr.com/GailMcMbreakin.html

Qbeam, I think you'll be just fine.

So now, exactly how do you plan to clean it (LOL): http://www.6mmbr.com/borebrushing.html