M1A Barrel Break-In

[Cobra]

I just recently bought a "loaded" M1A with the stainless steel national match barrel.  I was wondering if there was any break-in procdures, and if so, what they were.  Any help will be much appreciated

[ErikW]

There are probably more break-in procedures than there are rifles.

Ten pages of Google search results:

http://www.google.com/search?hl=en&ie=...barrel+break-in

[EricW]

[Heresy Mode ON]

Do the "break-in" procedures really accomplish anything?  I understand the end goal, but do they really do anything that just regular shooting and proper cleaning procedures won't?  Why shoot only 3 rounds then clean. (just as an example...) Why not shoot 5, 7, or 13?  Where do the magic numbers come from aside from out of some guru's derriere?

Could someone enlighten me?

E

[jkmccoy]

Back when I was dabbling with the quest for extreme accuracy from centerfire rifles (shooting a little High Power Silhoutte, some informal bench rest) I did some research on the break-in question. Following is the theory at least (I don't have empirical results to prove it). I did very carefully break in one heavy barrelled Rem700 with a PacNor barrel and it is incredibly accurate and cleans up very easily.

The bore of any barrel is not perfectly smooth. Better quality barrels are smoother, but there are still surface imperfections.  The bullets passing down the bore tend to smooth off the high spots and polish the barrel, but there is also the tendency to rub off bits of copper jacket. When the barrel is new there is more copper rubbed off on the bore. Subsequent shots tend to iron the bits of copper into the barrel and result in additional surface imperfections. By shooting a few shots and cleaning you get the maximum polishing effect with a minimum of ironing copper into the bore and wind up with a bore as smooth as possible.

With an M1A I would probably clean frequently for a while (after every 3-5 shots for at least the first 100 rounds). I suspect that it will help barrel life and make it easier to clean.

Cheers,

[EricW]

Thanks jk...

OK, I'm hip to your explanation.  That makes sense.

This isn't meant to seem argumentative here...

But, why not just cut out the middleman and lap the bore with a mild abrasive from the get go?  Or, fire lap the barrel with Tubb's magic grit elixir?  I totally agree that getting the roughness out of a barrel is a good thing - it did WONDERS for my .308, but I guess I question all the voodoo leading up to that end.  Why not slather the bore up with JB Bore paste and shoot it?  (Other than inducing excessive pressure....)  

I guess I'll have to buy 5 rifles and test out the various processes...  

[jkmccoy]

The various methods of lapping the bore are recognized by various of the extreme accuracy experts as useful techniques. The fire lapping procedure especially has many adherents. But most of the experts still recommend some degree of break-in. Apparently, no matter how fine the lapping compound you cannot achieve quite the same degree of surface finish with abrasive that you can with the burnishing action of the bullets.

I'll really be interested to hear the results when you build five identical bench guns and treat the barrels to different break-in procedures. I'll bet there are a lot of other people who would like to hear those results.

I'm not disagreeing with you. My sample size is one barrel, but the results of careful break-in were great (I cleaned after every shot for 25 shots, after every 3 for 100 shots, after every 5 for another 100). The best group that rifle has shot was 0.08" at 100 yards (five shots) and will always put five shots in less than 0.200". That barrel will also fire 50-60 shots with no measurable loss of accuracy and very little copper build up.

Could I have achieved the same result with fire-lapping? I don't know.

Cheers,

[Cobra]

Thanks for all the replies.  All the information provided here will surely help out this Sunday.

[EricW]

Sorry to mutate Cobra's post, but any of the rifle gurus care to chime in?

Kelly?  Patrick?

I'm kind of curious as to how you guys handle break in.  

E

[kellyn]

Derrick martin does not do any break in whatsoever.  "Go shoot it" was his response when I asked this question.  I do think there is a lot of voodoo about barrel break in and very little substantive test data.

I've done the break in thing with super duper quality barrels but to be honest outside of the benchrest world, I don't think it makes a bit of a difference.  Particularly with a semi-auto.  I no longer do it.

[Patrick Sweeney]

I've gone full circle, and have come back to what my Dad taught me: shoot groups and clean as you go.  (He walked across France and Germany in the Fall and Winter of 1944/45.  He knew a few things about rifle accuracy and practical shooting.)

Shoot a group, adjust the sights, clean the bore, shoot a group, repeat, the idea being that if (and IF) there is anything to bore breaking-in, you get some trigger and sight practice while you're doing it.

I feel there is a small segment fo the barrels produced where it helps.  A super smooth custom, hand-lapped bore isn't going to be helped much.  If at all.  A rough as a cob bore made on a Monday with tooling long since worn out and left standing since the previous Friday won't be helped at all.  Too rough.  in between, it may help.

On the other hand, if it makes you feel good.....

[EricW]

Pat and Kelly - Thanks!  I'd never heard of "breaking in" until about 10 years ago.  It never really made a ton of sense then or now.   Lapping, that I can understand...

[tightloop]

to each his own, but it might pay dividends to read what Dan Lilja says about it and also what the guys at Krieger barrels have to say.  

I do all mine like Mr. McCoy, clean every shot for 25, every 3 for the next 75, and every 5 for the next 100.  Now yu have to realize that I am a Townsend Whelen advocate when he says ,  "...only accurate rifles are interesting."  I have a 22PPC that will shoot in the .20's and has a Wiseman barrel, a 7Rem Mag that will shoot in the .30's, a .300 H&H that will shoot in the .20's and a .375H&H that will shoot in the .40's all with Wiseman barrels.  Also have some non-custom stuff that will do minute of angle, but nothing like those 4 custom rifles.

I am a believer in break in, but I used to shoot bench rest...another story.

[Shipster]

Here's my take on this subject.  Both Kelly and Patrick have very good points.  My break in procedure is a little different then Kelly’s.  I will clean after every shot for the first 10 rounds and then after every 3 for the next 90.  After my initial 10, I do what Patrick suggested, that is start my load development.  

My thought is when I'm spending $500 to have a Lilja stainless match grade barrel installed I want the best possible accuracy.  If you feel it's voodoo fine but as for me I'm not risking that kind of money just because I didn't follow the advise of the barrel Mfg. or the advise of a group of people that will probabley fire smaller groups then I will will only dream of (the benchrest shooters).

Good Luck Cobra

(Edited by Shipster at 6:09 pm on Nov. 7, 2002)

[kellyn]

True enough.  Some major barrel makers have very specific break in procedures.  And in the bench rest world, it might make a difference.  On an AR or M1A, really doubt it.  There is too much going on when the rifle goes off for breaking in to make a difference.

My dad and I both built .280 Ackleys.  He used a Shilen barrel and I used a Hart.  I spent a great deal of time breaking my barrel in (as in hours), he did not.  My .280 shoots .3 to .5 in groups and my dad's shoots .4 to .6 in groups.   I challenge any deer, highpower target, antelope, elk, steel plate (whatever the distance) to tell me the difference.  

I don't have anything against breaking in a barrel per se but it is an irrelevency in nearly all rifle sports, particuarly the practical ones.  You're not going to beat Bennie Cooley because you spent three afternoons breaking a barrel in.  You're not going to beat David Tubb  because you broke a barrel in but dropped 10 points offhand.  Spend the time shooting offhand or reading the wind or doing el presidentes.

[jkmccoy]

Kelly N,

I don't mean to disagree with someone with more experience and who would clearly stomp my butt in most any rifle competition, but I'm enjoying this discussion and I'd like to hear more of your thoughts.

Agreed, for the sports we are discussing (probably everything but benchrest) the difference in potential accuracy between a carefully broken in barrel and one that was just shot will NOT likely make the difference between winning and losing. Practice and shooting ability will.

But, my understanding of the break-in process (and desired result) is that breaking in a barrel not only improves the best possible accuracy, but reduces the build up of copper fouling and subsequent degradation of accuracy. That effect might be useful in an AR or M1A.

Many rifle barrels are very sensitive to copper fouling. I have a Win M70 Classic (new one) in .270 Win that is a great example. The first 5 shots from a clean barrel will shoot about a 2" group at 100yds. The next 5 shots will shoot about 3/4". It will keep shooting 3/4" groups for about 25 shots, then the groups will start getting larger (up to about 1.5" ). My guess is that it is a result of copper fouling.

That rifle that I was talking about earlier isn't some 14# bench gun chambered for 6mmPPC. That is my highpower silhoutte rifle (10# 1oz). It's chambered for .280 Rem. The load that reliably shoots .200" (five shots) at 100 yds is a 130 Sierra MK at about 3000fps. The first five shots from a clean barrel will be no more than .200", shots 55-60 will also be no more than .200".  It might last longer than that, I've never tried.

You also comment on the importance of practice vs. spending time breaking in a barrel. When I was shooting all those rounds and cleaning in between - I fired every shot at a target. I don't think that careful break-in of a barrel precludes practice. Fire a couple of shots and clean the barrel, but fire the shots at a target so that you get some benefit from it.

The only real disadvantage (that I can see) of frequent cleaning of an M1A or AR barrel is the possibility of wearing the rifling at the muzzle while cleaning. The rifle I was discussing is a bolt gun and it's easy to remove the bolt and insert a cleaning guide to prevent wear on the rifling.

With all due respect, if I had a brand new "loaded" M1A with the stainless national match barrel I would clean it very frequently for the first couple of hundred rounds.

Cheers,

(Edited by jkmccoy at 12:56 am on Nov. 8, 2002)

[Skalkaho Slim]

O.K., let's say for the sake of arguement, that a breaking in period is required.  I've already put about 50 rounds through my M1A w/stainless barrell.  My question is this:  Is it too late to begin the break-in process?  Should I just clean the heck out of it and start over?

Toujours Pret!

Slim

[kurtm]

SLIM:

It is never to late to begin the tedium of the break in. I think Mr. McCoy is about right on this one, just clean it frequently for the first couple of hundred rounds. If you clean it COMPLEATLY, ie no copper left in the barrle each time you clean it you are in fact doing a one round break in the next time you shoot it, you just happen to get more shooting in in between.

AS FOR AN M1A, GUYS, unless it is stage 5 bedded, and many other fine tuning accuracy tricks are done, NO ONE will EVER see any difference in accuracy of a BROKE IN barrle or one that is not!! As for fouling, we are talking STAINLESS here. With the higher sulfer and nickle content to make it machine easier it tends to be "softer" than Chrome Molly. With thurogh cleaning after each shooting session, it will "break in in about 200 rounds and be all it can be!                  KURT

[tightloop]

Kurtm

Softness in barrel steel is a relative thing.  I don't believe that stainless is "softer" than chromolly.  If that were so, stainless barrels would shoot out faster than any other and that is not the case.  In fact, stainless usually lasts 20 to 25% longer, given like calibers, same number of shots and the same cleaning procedures and frequency.

[kurtm]

Tightloop:

Yes barrle hardness is relative, metallurgy is not!! 416 Stainless ( commonly used for barrel making due to the properties I listed above), is usally through hardened to Rockwell 38C BEFOR machining, I.E. making a barrle. The HARDEST this type of "steel" can be through hardened is 40C. DON'T confuse through hardening with surface hardening, wich is hard to do with most ypes of Stainless. 4140, the most common Chrome Moly for barrle making, is through hardened to 40-42C BEFOR machining and can be through hardened to 58C. As a matter of fact the original G.I. spec for M14 barrles was AT LEAST 42C BEFOR machining. That sure sounds ( and in reality is ) harder than " stainless "!!!!!

The blanket statement of 20-25% more wear from stainless sounds VERY optimistic. This sounds like a statement that Blackstar rifle barrles made to sell more barrles!! Caviat Emptor!!!!! In reality it is more like 5-10% more with a really uniform 416 stock. This is now where we should take this to the Technical Forum but here goes.

The reason that Stainless seem to out wear Chrome moly, is two fold first with the high amount of sulfur in the mix it "chips" very uniformly (read this as machines precisely) and finishes very "smooth" compared to most carbon steels. Secondly the steel is protected with a molecular layer of Chromium Oxide, which is very hard ( about 65C) and cryogenically resistent ( can take A LOT of heat and cold). It is this resistence to heat I.E.1600 f, that realy HELPS stainless "live" longer. Also the abration resistence of Chromium Oxide is very high ( 65C). Chromium Oxide happens when the steel ( 416 w/ 12-15% chromium content) comes into contact with free oxygen I.E. air. This is also why scatched stainless doesn't "rust in the scratch. This microscopic coating is a constantly replacing layer due to the Chrome content of the steel, and the availability of air to oxidize it. In a rough LAYMANS terms we are shooting a "sort of chrome lined barrle. All of this info is probably on the "net" If you care to look, but untill Physics change in this universe and metallurgy takes a whole different turn, this should suffice.                                   KURT

[Skalkaho Slim]

I hope this doesn't sound like a stupid question, but here goes:

Does the "interior" (i.e., the surface that comes in contact with the bullet) of a stainless barrel become harder over time?  I guess what I mean to say is if I put 50 rnds (for example's sake) through it at every shooting session, will the heat and friction cause the steel to harden in any way?  I know that tempering involves higher temperatures than that produced by simply firing 50 rds, but I am curious to know if there is any "hardening" of the steel whatsoever over a significant amount of time.

I hope this makes sense.

Toujours Pret!

Slim

[tightloop]

since I am not an engineer, I won't do the research to see if you are correct or not...I will tell you that I have shot more than 50K centerfire rounds in competition and assuming the same caliber, bullet, cleaning procedure and frequency, SS gives you 3 to 4K more rounds of accuracy life than chromolly, per barrel, maybe more than that with the BR rounds like 22 and 6 PPC, I am talking big stuff like 308, 7Mag, 300 mag.  I don't care or give a hoot about the Rockwell scale hardness of the barrel steel blank.  Stainless lasts longer  than chromolly even if it is due to the continual oxidation of the barrel channel shot to shot and the subsequent "shot hardening" of the barrel.

perhaps my phrase-ology was poor, and indeed SS may be softer than chromolly, but it gives superior accuracy for a longer barrel life than conventional chromolly barrel steels.

[kurtm]

Slim:

Great question!! In a quick easy sort of way, there is a SMALL bit of hardening associated with firing. Unfortunatly it occures in the first few inches of the barrle just in front of the case mouth. After this area the thermal conductivity of the metal ( in this case stainless ) disipates heat faster than it can really work to harden the rest of the barrle. Stainless steels in this range are air hardening, in respect to SURFACE hardening, but you have to get them fairly hot, like right in the throat area. The problem here is that as I stated befor It is hard to surface harden stainless, I should have added UNIFORMLY. What happens is that you get some really hard areas, Chrome, and some areas softer, Nickle and Sulpher. This is why when a throat of a stainless barrle finally "goes" it looks like a gravle raod ( at a microscopic level ) as the softer areas are eroded away by the flame front of powder burning. Don't forget this is a VERY rudimentry explaination of what happens.

Tightloop:

I don,t give a hoot about Rockwell ratings eather!! As long as the barrle is hardend enough to machine well, is some what cryognicaly resitent, and is substantially "harder " than guilding material, it should be a good enough barrle.

3-4K more still sound incredibly high to me. The long range rifles we have built (I.E 100yd matches at Perry) in 300 win mag, seem to requier at least a barrle set back, or a new barrle, at right around 5000-6000 rounds( by the way we are talking STAINLESS HERE) to maintain match winning accuracy. The Chrome Moly barrles seem to go out around 4500-5000( yes some folkes still prefer 4140 barrles). Going by the values you quote stainless barrle should be winning matches with AT LEAST 7500-9000 rounds of ammo through them in 300 WIN MAG. I just don't see it.

YES STAINLESS STEEL BARRLE LAST LONGER!!! I AGREE!!! but it doesn't seem to be quite as much as some claim. As for SUPERIOR accuracy attributed to stainless, don't tell the guys that are still winning with chrome moly barrles, it might make them feel bad!!!        KURT

[kurtm]

I'm sure I'll hear about the typo on the 100yd matches at Perry!!! Darn fat fingers!! How about 1000 yds instead.                                          KURT

[kurtm]

Slim:

ERROR!! I goofed up!! the wear pattern in the throat area I attributed to Stainless is actually the wear pattern found in Chrome moly barrles when shot out. ( gravelly ) due to the softer parts of the mix migrating under heat to the surface. The flame front then erodes these softer metals out, hence the gravel look.

Stainless DOES NOT under go as much migration of molecules in the mix, instead "spot hardens" as stated, but pressure erosion and heat causes the throat area to "check", small microscopic cracks. These cracks are in general smoother than the erosin pattern of chrome moly and may account for the slightly extended barrle life of stainless as well.                   OOPS!!!!  KURT

This showes what happens when you try to work off the top of your head instead of doing some quick review, as I should have done and finally did!!

[Scooter]

There's an article by McMillan saying that the whole concept of break-in for a rifle barrel was suggested by barrel makers to increase business.  The idea is to get the person to fire a X number of rounds prior to using it for competition.  Since competition guns have a limited life span for the barrel, they just reduce the number of rounds for the barrel.