Bore polishing (NOT firelapping)

[Molly]

I stumbled across another neat little trick that may interest the PP crowd. It's a take-off from something I wrote up for the CBA a while back, but here's the whole story:

Some time back I bought one of the unfired Yugo 8x57 Mausers because they were such bargains. But when I got the cosmoline off of it, the bore was pretty rough. Not rusted, not pitted, but it looked like it had been finished with sandpaper.

I didn't want to throw it away, and at the same time, I didn't want to pour coarse abrasives down a new barrel as was recomended for conventional firelapping. I decided to try something a bit less radical, and used JB Compound on a bore mop the coat the bore of the rifle. Then I fired a light jacketed bullet load, used the mop again, fired another light load, etc. When I was done, the bore looked like a mirror, and without any noticable enlargement. I wrote it up, and several people have tried it with excellent results.

A recent discussion of various grades of paper for PPing and various PP lubes brought the experience back to mind, because I wondered if anyone appreciated the fact that TiO2 - added to make paper whiter - is also a very, very fine abrasive. You can get the idea if you just walk over to the wall of your room and rub it with a nickle. It'll generally look like you wrote on it with a pencil, becaue of the metal polished off by the TiO2 (& other pigments). I'm a retired paint chemist, and I knew about this, but just didn't make the connection before.

Anyhow, my first thought was to wonder if anyone had noticed any polishing effect from ordinary PP lead bullets. Then I put two and two together, and wondered what would happen if I 'lubricated' PP cast bullets with JB compound! Just finger rub it into the PP after wrapping, drying and sizing. Works great, and without all the trouble of the bore mop approach.

I wasn't trying to develop a more accurate load, and didn't test for accuracy (I shold have, but didn't.) I was trying to test another approach for polishing bores, and I got that in spades. FYI, I used a moderate load with wheelweight alloy in a 30-06. Nothing fancy, but it worked fast, easily and well.

So if you've got a rifle (or pistol for that matter) that's prone to fouling or leading, you might want to give this a try. If you happen to have a bore that has been rusted, it MAY be possible to salvage it like this, using an appropriate grade of very fine abrasive polish. I'd recommend that you steer well clear of the coarser abrasives often recomended for fire lapping. For some reason, the very fine abrasives like JB compound seem quite effective here, and polished the bore of the Yugo M48 in about 5 or 6 shots. I see no advantage to coarser abrasives, and I can see numerous potential problems they could cause.

Of course, the usual caveats apply: These results were obtained using components, equipment and techniques that will differ from yours, so approach this experimental procedure with great caution if you decide to evaluate it yourself. NEVER use experimental procedures of this nature - or any nature - with maximum loads unless you work up very gradually because the interactive effects could produce dangerous pressure levels. Since you are the only person controling most of the variables involved, you will have to accept full responsibility for the results of your judgement and practices.

Regards,
Molly

[bcp477]

Interesting. I also shoot an M48, but one which I rebarreled recently, with a pristine, unmounted military surplus Yugo barrel. On my previous M48 barrel, I carefully "lapped" the bore with JB bore paste, after cleaning out all of the visible crud, as it was quite rough in the beginning. This was much more than simply cleaning the barrel with the JB - I really worked it over. This definitely made an improvement in the appearance, as well as the accuracy of the barrel. The process made a well-pitted barrel into a pretty good one.

As for my "new" M48 barrel, I have not followed the same procedure, as this barrel is in marvelous condition, especially for it's age (and thus, doesn't need it). But, I have noticed that, after shooting my paper-patched bullets, the bore is remarkably clean. I patch with white, lined notebook paper....and lube with Lee Liquid Alox. Perhaps the white paper is having a polishing effect on the bore, I do not know. In any case, I certainly do not object to the clean bore after shooting, as it just makes things easier.

[Molly]

Interesting. I also shoot an M48, ... On my previous M48 barrel, I carefully "lapped" the bore with JB bore paste, ... This definitely made an improvement in the appearance, as well as the accuracy of the barrel. The process made a well-pitted barrel into a pretty good one.

As for my "new" M48 barrel, I have not followed the same procedure, as ... after shooting my paper-patched bullets, the bore is remarkably clean. ... Perhaps the white paper is having a polishing effect on the bore, ...

The results with your first barrel are no surprise. But it's a shame you had to do it all by hand. Believe me, I've been down that road, pouring laps, etc. It's a BUNCH of work. Half a dozen shots of light loads using JB compound is the easy way to do it.

It wouldn't surprise me a bit if you aren't getting some slight polishing effect from the PP in the second barrel. The TiO2 levels in various grades of paper will vary considerably from grade to grade, and there are other pigments (clays, etc) that probably make a contribution as well. I can see several explanations off the top of my head: First, the PP helps clean the fouling residue from each shot, and 2nd, each shot polishes the bore a trifle more, making it less likely to foul, and 3rd, paper simply doesn't have the fouling potential that cupronickle has. Any combination of these could be at work, and who knows what else? Hmmm. Anyone out there work in the paper industry that might be able to comment on levels of additives in different grades of papers?

Regards,
Molly

[Digital Dan]

You can achieve the same result by firing mild loads with an unlubed paper patch, or dry paper. Half a dozen or so shots will turn a gray bore shiny.

Glossy papers are generally so due to the inclusion of kaolin in the mix. It is a clay like material commonly used in paints and other pigments....and cat litter. It is very abrasive, use at your own risk.

[405]

Is there any real difference? Seems like relative matter of degree. Kinda like- Is it sanding with 60 grit sandpaper but polishing with 2000 grit sandpaper?

[Molly]

Is there any real difference? Seems like relative matter of degree. Kinda like- Is it sanding with 60 grit sandpaper but polishing with 2000 grit sandpaper?

Actually, they ARE the same process, differing only in degree. But that difference is important: It's the difference between someone using a rock to scar up your windshield, or using some polish to clean the windshield, or make the paint gleam. Both are fundamentaly abrasion, but I know which I'd rather have done to MY car.

Molly

[Baron von Trollwhack]

Some hold that a barrel can be too smooth, thus suffering from lube failure and fouling, to the degradation of ACCURACY. BvT

[sagamore-one]

I used a similar approach on a Blackhawk in 45 colt . The barrel was sooo rough that even jacketed bullets leaded the bore... well almost that rough. I destroyed my Lewis lead remover trying to get the lead out. The good people at Ruger examined it and told me there was "heavy duty machine marks" in the bore and that my cast linotype alloy boolits were too soft, that I should use jacketed only. I cast up some nice Keith s w c boolits, hand applied J&B to the lube grooves, and loaded them up. After 25 shots the bore started to clean up. It may have been an agressive method... but it worked. Much more satisfying than dealing with customer non-service at Ruger.

[Molly]

Some hold that a barrel can be too smooth, thus suffering from lube failure and fouling, to the degradation of ACCURACY. BvT

So I have heard, particularly in the context of black powder ML rifles. However, I have never seen, much less had opportunity to examine such a case. Nor have I ever heard a reasonable explanation why this might be so. I personally regard it in a class with 'leading is caused by lead rubbing off as the bullet goes down the bore.' In other words, someone dreamed up and put forth as factual, without a shred of evidence or logic that I have ever been able to discern.

And before you condemn a barrel as 'too smooth', you might reflect that - without a single exception that I know of - the master gunsmiths of the muzzle-loading era hand-lapped their bores for the greatest smoothness possible. This is a very tedious and labor intensive process. I've done it. And I assure you that while someone MIGHT try it once just out of curiousity, there won't be many willing to do it again if the smoother, more uniform bore didn't help.

Molly

[405]

Seems like an excercise in subjective semantics. Without some standard index of what is being talked about when reference is made to this, that or the other abrasive agent.... any discussion of lapping, grinding, finishing, sanding, polishing, burnishing, etc. is of no use. It appears that the transition from say grinding to sanding to lapping to polishing is a continuum. One person's finishing may be another's lapping. One person's lapping may be another's polishing. A base standard would be helpful. Even if it were arbitrary.

FWIW, my standard for fine, final polish for bores or dies is around 600 grit to around 2000 or finer. For example: I have no idea what the relative grit size or abrasive index is for kaolin or TiO2 or cotton paper or JBs or Rem Clean or cotton cleaning patches or whatever else is mentioned. I think they would fall somewhere into my fine polish category. However, when the emery cloth or sandpaper or jar of compound says "100 grit" or "320 grit" or "600 grit" or "1200 grit" I know exactly what that means. There are standardized tables that reference grit sizes in microns.

Abrasive index is yet another concept which is glossed over here but would only confuse the matter more.

Many of the firelapping kits, compounds or bullets available appear to cross over between what has been called lapping (on this thread) and polishing.

I don't know if a bore can be too smooth?? Maybe. But I do know that too rough a bore is not good either. I also think, based on what I've noticed, some new hand-lapped bores do smooth out fairly quickly from shooting/cleaning- a sort of break-in thing after about 10-30 rounds. Some new bores that were not hand-lapped will get slightly smoother or at least foul less after a certain, unknown number of shots and cleanings- usually more rounds than the lapped bores. Some new bores that appear to be rough with all manner of tool chatter marks will shoot amazingly well and do not foul any more than a lapped bore from the first shot on---- go figure? I think but can't prove of course that the bore's relative smoothness, within reason, may not be as important as a consistent dimension from breech to muzzle, at least concerning accuracy potential. I think that is easily measured with an air gauge and some makers state the bore variance standards for their barrels. Throat erosion/land wear in used bores and basic "crookekness" or "runout" in all bores are yet other absolute accuracy busters but adding them to discussion may muddy the water if trying to stay on the smoothness, polishing topic.

[Molly]

Seems like an excercise in subjective semantics. Without some standard index of what is being talked about when reference is made to this, that or the other abrasive agent.... any discussion of lapping, grinding, finishing, sanding, polishing, burnishing, etc. is of no use. It appears that the transition from say grinding to sanding to lapping to polishing is a continuum. One person's finishing may be another's lapping. One person's lapping may be another's polishing. A base standard would be helpful. Even if it were arbitrary.
....

You know 405, when I started this thread, I had no idea it would degenerate into this sort of nitpicking. While I am compelled to admit the technical accuracy of what you say, nonetheless I would argue that there is room for a little common sense here. For example, the electromagnetic spectrum is continuous from well below visible light through radio and x-rays - and well beyond. This is a fact, just as the graduation from sanding through polishing is continuous.

But you know, if someone snaps off the wall switch, I've got enough sense to know that they turned off the lights. And that the radio will still work, as will the doctor's x-ray equipment.

By the same token, I can look at the surface of a piece of steel and tell you whether it's been sanded, smoothed or polished. It may be just a matter of degree in all instances, but the difference is neither ambigous nor argueable for most folks. The difference is DOI, or distinctness of image. Try these definitions on for size:

If there are no visible scratches or abrasion marks, and it looks like a mirror, - or approaches that level of image replication, it's polished.

If there are no visible scratches or abrasion marks, but there is only a vague image detectable, with little or no visible details, it's smooth.

And if there are visible scratches and abrasion marks, with no visible image refelction at all, it's a sanded or worse finish.

And if you demand more precise definitions, let me introduce you to a reflectometer, which will measure - reproducably and precisely - the smoothness of the surface of most any reasonably smooth object, from dead flat wall paint to the aforesaid mirror. It will provide you with the required (and industrially recognized) 'base standard' that is not subject to individual eyesight or judgement. It comes complete with calibration standards and instructions. However, very few people will have any idea what you are saying when you say that you require a 90% reflectance at an included angle of 60 degrees to qualify a surface as polished. I recommend that we revert to the common sense definitions above for the purpose of this discussion - which, BTW, was NOT what consiitutes lapping, it was an easy way to get a shiny bore.

Regards,
Molly

[405]

No knat poking. Some will read the ads about firelapping compounds and bullet kits and such and may get the wrong idea after reading all this that those things use some terrible coarse grit that is somehow grinding the bore smooth instead of the more gentle polishing as described with the JBs or papers with clay additives. Couldn't agree more about your approach-- "use the least aggressive method that shows some result and don't overdo any bore polishing" or something to that effect. OR just shoot and clean as usual- it's all many bores need to reach desired smoothness and live a normal, long and hopefully accurate life. And yes, hand lapping/polishing is labor intensive.

[Molly]

... Couldn't agree more about your approach-- "use the least aggressive method that shows some result and don't overdo any bore polishing" or something to that effect. ... - it's all many bores need to reach desired smoothness and live a normal, long and hopefully accurate life.

Couldn't have said it better myself. Thanks.
Molly

[Molly]

Gentlemen,

I'm pleased to tell you that Joe Brennen would like to add this thread (or more accurately, an edited, spelling corrected version) to the next edition of his book. As a matter of courtesy, as well as avoiding potential legal problems, this will require permission to quote from those who commented here. And probably from the Cast Boolits forum folks too.

I'm assuming that very few would object, since it just spreads their contribution (already public on this board) to more folks. So we don't swamp the thread with a hundred messages that read "Sure, go head", how about letting me know if you do NOT want to be quoted. Out of respect for the posible privacy concerns of the contributors, I won't add handles (or real names) unless specificly requested. - If so, send me a PM. But since this IS a public forum, and it's address will be cited, anyone wanting to find who wrote what will have little trouble anyhow.

OK, there it is. Let me know if you do NOT want your contribution to be included or referenced. Authorship will be cited by name or handle if specificly authorized.

Regards,
Molly

[405]

No problem by me. Credits, etc. not necessary and not wanted. Don't know if anything I posted was quote-worthy but no worries whichever way. Use at will...

[joeb33050]

[QUOTE=405;357917]Seems like an excercise in subjective semantics. Without some standard index of what is being talked about when reference is made to this, that or the other abrasive agent.... any discussion of lapping, grinding, finishing, sanding, polishing, burnishing, etc. is of no use. QUOTE]

Back when I was a mechanical inspector, during the first Hoovuer administration, we measured surface finish in "RMS Microinches", where "RMS" means "root-mean-squared", or what we call "standard deviation"; and where ?microinches" = millionths of an inch. I learned to check surface finish against coupons that had a known finish, where 8 microinches was a polish, and 32 microinches was a little grainy. Today a "profilometer" makes these measurements, and the coupons are pretty much gone. Profilometers came in as I was going out of the business, to school.
So there is a standard index, "microInch RMS".
joe b.

[joeb33050]

Some hold that a barrel can be too smooth, thus suffering from lube failure and fouling, to the degradation of ACCURACY. BvT

I found an article by H. Warner on this topic, in an old gun mag. It's long, I got a copy and sent it to Molly.
I was able to scan a page and get a WORD file, needed some cleaning up but was much easier than one-finger typing. Can/will anybody scan a copy so I can put it up here?
Thanks;
joe b.

[joeb33050]

I found an article by H. Warner on this topic, in an old gun mag. It's long, I got a copy and sent it to Molly.
I was able to scan a page and get a WORD file, needed some cleaning up but was much easier than one-finger typing. Can/will anybody scan a copy so I can put it up here?
Thanks;
joe b.

Meant, I was ONCE able to .....; can't do it now.
joe b.

[joeb33050]

From "SHOOTING AND FISHING", July 5, 1888
THE AMERICAN RIFLE
(Development of 40 years)
BY H. WARNER
(Copyrighted)
FALLACIES ENTERTAINED BY RIFLEMEN.

In these days of almost universal rifle practice by the young and middle-aged men of the United States, and the interminable discussion of questions incident thereto, one would naturally suppose that the requisites for a fine shooting rifle should ere this be well defined and fully understood by the majority of our marksmen.
Yet this is not the case. There are certain characteristics generally supposed to be indispensable in the make-up of a perfect shooting rifle, because so often described and dilated upon by would-be authorities on the subject, that the shooting world has come to regard them as necessary, or in the line of facts established, which may govern in all cases.
Many of the conclusions thus forced upon the shooting fraternity are misleading in their nature and at variance with facts.
Fallacy No. 1. -Among the fallacies thus established, none is more prevalent than the belief that a rifle designed for the finest shooting must be finely finished on the inside of the barrel.
Mr. W. W.Greener, of England, in a work on rifles thirty years ago, fully committed himself to this theory, and more recently Dr. E. H. Pardee, a noted rifleman on the Pacific coast, in a dissertation on "Ancient and Modern Fire Arms" (published in the Breeder and Sportsman of San Francisco, Cal.), reiterated the same opinion, in words so like those of the author first named, that they would appear to be a quotation without credit.
It is doubtless safe to assert that ninety-nine out of every one hundred marksmen of the present day adhere to the same belief. For, what is more common amongst riflemen after examining the inside of some new gun just brought to their notice, than the remark: "That gun is finely finished inside. It must shoot well! See what a polish it has!"
Notwithstanding this unity of opinion and general belief in the efficacy of high polish as an adjunct to fine shooting. I make the assertion that an extremely fine finish on the exterior of a rifle barrel is not necessary, nor even desirable, for in many (if not most) cases it will be a fruitful source of erratic shooting.
If asked to give my reasons for drawing such a conclusion, the most natural and direct answer would be that it is the result of repeated test and experiment-simply, I have found it so in practice.
To the inquiring mind such an answer would probably be unsatisfactory, and, if still disposed to controvert the deductions arrived at by experiment, and, ask me to explain why a high polish should give inferior results in shooting, the answer must necessarily partake largely of nature of opinions or theories, the correctness of which it would be difficult to demonstrate or establish in any other manner than by experiment. Theories can never stand when opposed to facts, but a little elucidation of both may serve to modify a seeming difference, and bring them nearer together.
In this view of the case I will proceed to give some other reasons for the faith that is in me.
All who are familiar with the subject will agree: First-That uniformity of condition, in gun and ammunition, during a series of shots will be more conducive to uniform shooting than a varying or changeable condition of the same.
Second-That in repeated firing, heat is the most important, if not the only element that enters in to disturb the normal condition of the gun-that friction generates heat, and therefore, the rapid passage of the projectile along the inner walls of the rifle barrel must be regarded as an accessory to the heat developed by the explosion.
This combined action of the two agents produces a heat most intense, and its influence on the barrel and projectile being as rapid as thought, it would, if of any considerable duration, be sufficient to melt a leaden projectile, but the passage of the bullet out of the barrel being so short, it seldom terminates in melting, although I have thought on two or three occasions, several years ago, that I obtained such results with extremely heavy charges of powder, in a long, heavy-barreled rifle having a chamber in the breech much larger than the bore of the gun. Be this as it may, the effect of heat on all, or nearly all, metallic substances, is to expand and soften them, more or less, according to the intensity of its application. It is not, then, unreasonable to suppose that its influence as applied in the process of discharging a rifle would be sufficient to materially change the density, size and fit of the bullet. Such changes would affect the flight of the bullet just in proportion to their magnitude, and their magnitude would depend entirely upon the amount or degree of heat developed.
Heat, then, seems to be the chief obstacle we encounter in our efforts to secure uniform shooting. Could we find an explosive which developed no heat, and a projectile which encountered no friction, we should have made a decided advance in the science of gunnery.
Since we are unable to overcome the influence of heat, the best we can do is to reduce it to a minimum. It is plain we cannot dispense with, or greatly modify the explosive in general use to-day, and therefore cannot hope to make much reduction in the heat developed from that source. There seems to be but one direction in which we may look for improvement.
As I have previously stated, friction generates heat, and the friction of the bullet in passing along the barrel is therefore a natural ally of the explosive in producing an element so detrimental to uniform shooting, and, the worst feature of it is, that the very considerable augmentation of heat thus produced, occurs in the very spot to make it most disastrous (i.e.) on the abrading surfaces of the patch, and culminating near the muzzle of the gun, where it is so desirable that the delivery be easy and perfect.
This frictional heat is often so intense as to scorch and weaken the patch. It is to be deprecated always, and guarded against as well as circumstances will permit. Hence the frequent resort to lubricants of some kind by many of our prominent marksmen. From the above it would appear that whatever tends to reduce friction, or render it uniform, is an aid to good rifle shooting, and this brings me up to the point under discussion, and the proposition previously stated, to wit: "Extremely high polish is detrimental to fine shooting."
I make this statement as a fact, substantiated by thorough test, but I offer in explanation to those who doubt it, the assumption that two surfaces finely finished and perfectly fitted to each other will adhere to each other more firmly and produce a sharper friction when moved rapidly and forcibly across each other than they would if the surfaces were more coarsely finished.
In point of fact, two pieces of fine metal with flat surfaces may be so closely fitted to each other as to make it extremely difficult to separate them, or to slip one upon the other. Two surfaces fitted so closely as to exclude air or any other substance become almost like a solid piece, and the same principle holds good when applied to a gun and its projectile.
If the inner walls of the barrel be polished down to a finish so level and smooth that there is no scratch on the surface deep enough to contain air or lubricant while the projectile passes over it, the result will be extreme friction-great generation of heat-a burnt patch (if there be one to burn) and an erratic shot, quite frequently, for it must be remembered, that the explosion of the powder will upset and fit the bullet to the gun, although it may not have fitted closely when put in. After the explosion the surface of the bullet will conform exactly to the surface of the gun, even to the exclusion of air which might have been between them before, and the fit thus made is not likely to become any looser on the passage out. On the contrary, the heat, generated by friction, as well as that imparted by the burning powder, would have a tendency to expand the bullet and make it fit more tightly if possible. It is this tendency to expand, and present increased obstruction to the propelling forces, thereby inducing a second upset of the bullet on its passage out, that results in wild shooting.
This expansion by heat is more likely to occur in highly polished guns than in those of coarser finish, which give better facilities for lubrication, or the presence of a little air occasionally between the surface of bullet and walls of barrel.
Amongst riflemen of ripe experience it is well understood that that guns by much use become (to use a common expression) "shot out" (i.e.) there is a falling off in their shooting qualities. This is usually ascribed to a worn condition of the interior, that is, to a certain extent, true; but not in the ordinary acceptation of the term worn; for, while the rifling may still be of proper depth and form, to give good results, the surface has, by continued wiping out and shooting, acquired so high a polish as to prevent it. One who is familiar with this phase of gunnery will have no difficulty in detecting it, even without looking through the rifle, as he will readily detect it in wiping the gun, or even in the report, if he listens carefully for any considerable number of shots.
The remedy in such cases is to carefully work over the surface again with proper tools in such a manner as to break up the high polish and replace it with a coarser finish.

[bcp477]

As for permission to use my comments (I doubt that MY comments were those intended to be used...but I thought I'd answer, just in case)....it is fine by me. Certainly, no "credit" needed.

As for the article included by the last poster.... literally everything is a matter of degree. I certainly agree that polishing or lapping a bore does NOT guarantee anything (an improvement of accuracy or even easier cleaning, etc.). So, I for one will not argue that this procedure (bore lapping) is always of value. Sometimes it will help - sometimes not. If done badly, i.e., too aggressively, it can even be detrimental. No one can say, without ever being contradicted, that a smoother bore will always perform better than a rougher one. All I can say is that it DID have a positive effect on my previous barrel. As my "new" barrel is in such good condition as it is, I have no plans to put forth the effort of "lapping" the bore. Bore lapping, like most procedures involving firearm accuracy, is NOT a panacea or "miracle cure". It is only a technique that can sometimes help, nothing more. Taken in that context, there is never any need for splitting hairs in such discussions as this, or arguments on the matter.