M1 Garand: Measuring TE Using ME Gauge

[M100C]

I'll bet this is one question no one has asked. It also makes me out to be the cheap guy I am ...

I cannot find a technical explanation of throat erosion. I expect it is a measure of the depth, from the top of the chamber to the point where the inside diameter across the lands measure 0.300". I have used a TE gauge several times, so I know how to take the measure, but I cannot say I know (or remember) geometrically what is being measured.

Why I ask? Well, I am short a TE gauge, and would like to measure/estimate TE on a barrel. However, I have an ME gauge which drops into the chamber unobstructed, and - using the wringing of standard thickness gauges (totalling 1.48"), and the overall length of the ME gauge to the 0.300" mark (1.93"), I guess I may be able to know (or estimate) the TE measure. I have seen TE/ME gauges with both measures off the same taper, so there ought to be a geometric relationship. Anyone ever do this, and if so, do you have a way to interpret a TE measure using an ME gauge?

If anyone knows of a technical measure, I can do the math and post back an answer.

 

[fguffey]

Using the wringing of standard thickness gauges

I cannot find a technical explanation of throat erosion.

I would not have got involved but you said ‘wringing’.

I have machines that make gages from head space, pilots, taper etc. When it comes to technical explanations and “all you have to understand” is the number on the gage. As you said in the perfect world the diameter of the bore is .300”, in the real world and before the rifle is fired the taper gage will indicate .301”. What does that mean? When using a taper gage the bore diameter is measured at the beginning of the lands. In the perfect world all throat erosions has the same taper.

Then there is the other end of the barrel the muzzle, reloaders and smiths claim the taper at the bore is caused by bad habits when cleaning the rifle. It is said the taper at the muzzle is caused by the cleaning rod. I do not agree but there are gages that measure the diameter of the bore at the muzzle. The muzzle gage comes with numbers; the numbers are to be read by adding the number to the diameter of the gage. If you are able to measure the diameter of the taper at the rings the reading on the micrometer should agree with the number.

Years ago I made a barrel cleaning system, it is muzzle friendly, I made in just in case the cleaning rod was causing the taper. Before that I ground the joints of the cleaning rod smooth and then taped them.

Then I have a picture, the picture was recognized for art sake and won a prize. I believe the picture proves muzzle taper is caused by hot high pressure gas cutting the muzzle.

F. Guffey

 

[Jim K]

Well, I don't make my own gauges, but maybe I can explain a bit what TE is and how and why it is measured.

The throat is the area of the rifle barrel just ahead of the chamber neck. When the chamber is reamed, that part is taper reamed to allow the bullet to fit when the round is chambered. How much it is reamed and the exact taper depends on the bullets to be used. The tapered area is also called the "leade."

When the cartridge is fired, gas first expands the case neck to allow the bullet to be freed. But the bullet does not immediately move because of its own inertia. Instead it just sort of sits there, like a couch potato, while gas flows around it. That gas, flowing around the bullet, is what causes erosion. Since it is pushing through a small area, its velocity increases, and the heat of the gas combined with small particles of burning powder erodes the throat and leade. Finally, the bullet decides to move, pushing into the leade and into the rifling, sealing off the gas and stopping erosion.

But every shot will result in some throat erosion. It can't be stopped, and it will grow. Each firing increases the erosion and each lengthening of the eroded area will increase the distance the bullet has to move before it seals off the gas. Since erosion keeps moving forward, its extent can be measured with a gauge by seeing how deep the gauge goes into the barrel, measured from some outer point, like the edge of the receiver ring or the edge of the chamber.

So why is that important, other than some rough looking area in the throat? Well, the bullet is just moving out of the case when it hits the eroded area. If that area is too large (which it will be after while), the bullet can skew sideways, and enter the rifling crooked, and that distorts the bullet and raises hob with accuracy.

Now what about muzzle "erosion". Well, there is no such thing; the muzzle is so far from the chamber that the gas has cooled down and the bullet is a tight fit in the barrel, so erosion doesn't take place. The correct term is "muzzle wear", and it almost always comes from one source, the cleaning rod. It rarely is a problem with rifles that can be cleaned from the breech, but some rifles, like the M1 and M14, cannot be easily cleaned from the breech, so the cleaning rod, plus any dirt and crud it picks up will damage the barrel if applied too often. Steel military cleaning rods are often blamed for muzzle wear, but oddly enough aluminum or brass rods do more damage since they pick up and hold dirt and abrasives more than the steel rod (which is softer than the barrel steel) does. If it is necessary to clean an M1/M14/M1 Carbine very often, a bore guide should be used to prevent the rod from scraping on the rifling and creating muzzle wear.

So, can you use the same gauge? I am not sure how. The area the TE gauge measures is at the front of the chamber, three inches or so from the breech which means the measuring part is at the end of the gauge. The MW gauge is much shorter, so it can't be used as a TE gauge. Can the reverse work? Not well. The longer gauge can be used for an educated guess, but there are no markings on it to get a real idea of muzzle wear. Generally, MW can be judged by using just a bullet and observing how far it goes into the barrel of the test rifle vs another barrel that is new or known to be good.

HTH

Jim

 

[Reloadron]

In addition to Jim's fine description this is a good read and explains the numbers with a few dimensions. Jim also makes a good point where they refer to TE (Throat Erosion) and ME (Muzzle Erosion) but in reality the muzzle shows wear and not really erosion.

Ron

 

[Kp321]

I am able to use a TE gauge to read MW by adding a spacer, a section of 8mm barrel, that I faced off to the proper length to read zero on a new 30 cal barrel.

 

[fguffey]

I am able to use a TE gauge to read MW by adding a spacer, a section of 8mm barrel, that I faced off to the proper length to read zero on a new 30 cal barrel.

Why are you using a spacer on a throat errosion gage when measuring muzzle ware? The OP said he was;

using the wringing of standard thickness gauges

I do not find it necessary to use 'wringing' or spacers but as Reloadron said;
it is good reading.

F. Guffey

 

[rcmodel]

I have to disagree that cleaning rod wear is not a factor in muzzle wear.
Especially on military rifles.

The GI issue jointed steel cleaning rods are very rough on the outside, and each joint is a mini broaching scrapper.

Further.
I have owned enough 100 year old Winchester lever actions to learn this.

The nice ones with shiny bores are rare. But they indicate compulsive cleaning in those day of chrossive primers.
But they almost invariably have worn out muzzles.

The black bore beaters usually have strong sharp muzzle rifling.
(Because they saw very few cleaning rods in thier life.)

rc

 

[fguffey]

The GI issue jointed steel cleaning rods are very rough on the outside, and each joint is a mini broaching scrapper.

And the old timers did nothing but continue warring away metal. Again, the joints were a bad fit, I ground them smooth and then taped. After that I made a cleaning system that would not lock up or jam and there was no way it could stick in the barrel like the bore snake. Now forum members are using case necks for guides.

I have a picture, it has nothing to do with guns or arsenals but the picture won a prize and was published in a book of famous photographs. I thought it was a picture of everything we do not know about the moment the bullet leaves the barrel.

And now I will assume no one understands what is being measured when a throat erosion gage is used.

If anyone knows of a technical measure, I can do the math and post back an answer.

I'll bet this is one question no one has asked. It also makes me out to be the cheap guy I am

I will bet you it has, at the end of the thread no one knew any more when the question was asked than they did at the end of the thread.

When the theme of the thread hovers over ‘it can not be done’ I think of John Godfrey Saxe and the elephants, a lesson in the theory of Manifold Predictions.
http://www.jainworld.com/literature/story25.htm

The OP is looking for a tool that measures the taper, I have gages that have tapers and none of them will measure a taper. I have sent taper gages to a number of members on different forums, the first thing they had to understand is; it is not a taper gage it is a hole gage, again, the gage has a taper but does not measure a/the taper.

I have tapered pins, I have tapered reamers and I have tapered taps; for all of that to work all of the tapers must agree.

F. Guffey

 

[Jim K]

"I will bet you it has, at the end of the thread no one knew any more when the question was asked than they did at the end of the thread. "

Well, I tried. Perhaps Mr. Guffey will enlighten us in his usual clear and concise manner as to just what TE is and how it is measured. I am sure we will all benefit.

Jim

 

[rcmodel]

I know I sure would!!

rc

 

[fguffey]

Well, I don't make my own gauges, but maybe I can explain a bit what TE is and how and why it is measured.

That is not the problem; no one knows 'what it is' they are measuring.

F. Guffey

 

[fguffey]

Well, I tried. Perhaps Mr. Guffey will enlighten us in his usual clear and concise manner as to just what TE is and how it is measured.

What did you try? The OP wants to measure the diameter of the barrel at the muzzle; the problem is the possessive nature of the M1 experts, if they understood the function of the throat erosion gage we would not be having this conversation.

A tapered gage measures the diameter of a hole. The taper allows the gage to be installed into a hole until it stops.

The M1 throat erosion gage is a tapered gage, it does not measure the taper caused by erosion, it measure the diameter of the bore; that makes the M1 Garand TE gage a hole gage. The taper allows the user to measure the diameter of the bore in .001” increments. For most it appears complicated. The taper at the throat and or muzzle must be less than the taper of the gage; less taper allow the gage to be placed into the bore. The gage stops when the taper contacts the bore regardless of which end of the bore is being measured.

I have said I am the fan of transfers and standards. The TE gage used on the M1 is a transfer and a standard. Many Internet reloaders have purchased pin gages. 1 tapered gage can take the place of 10 pin gages when going from .301” to .310”. To keep it neat the distance on the taper between .001” and .010” is 1.000”. It is not possible to read the gage because visibility so the tool is designed to be read on the protruding end of the gage.

Quote:
I am able to use a TE gauge to read MW by adding a spacer, a section of 8mm barrel that I faced off to the proper length to read zero on a new 30 cal barrel.
Why are you using a spacer on a throat erosion gage when measuring muzzle ware? The OP said he was;
Quote:

using the wringing of standard thickness gauges
I do not find it necessary to use 'wringing' or spacers but as Reloadron said;
it is good reading.

I have never thought it strange the M1 Throat Erosion gage is it; made for the 308 barrel with a bore of .300” and its use is limited by M1 experts. If the owner of a throat erosion gage wants to measure the diameter of the muzzle spray/paint the gage with Persian blue or purchase a felt tipped pin with black ink and paint the gage. And then; place the tapered gage into the muzzle until it stops. Contact between the gage and bore should leave a mark. All you have to do after making the mark is measure the diameter of the taper at the mark with a dial caliper.

Then we have to go to a language that is understood; The M1 Throat Erosion gage assigns a number from 1 through 10; the number indicates the amount of ware/erosion above the bore diameter in thougandths.

Then there is chamber casting. That is another topic that “it can not be done’ hovers over the thread.

F. Guffey

 

[nofishbob]

I am not an expert at TE or MW gaging or the dynamics of the wear and/or erosion in these areas. I am, however pretty familiar with measuring all sorts of physical dimensions in an industrial and lab environment.

From the OP's post, it seems that he wants to measure the distance from the chamber of a 0.300" diameter datum. The idea being that the farther away from the chamber this datum moves, the more TE has occurred.

This is not measuring taper, which is the angle along a cone-shaped surface from a cylinder. Typically we take two diameter measurements a known distance apart and derive the angle from that.

I don't assume that TE will produce a straight cone-shaped erosion pattern, so taper is really not what we should be concerned with.

Does it matter from an accuracy standpoint how large the bore has eroded near the chamber, or is the intent only to see how far down the bore the ID is larger than 0.300"?

The idea that one cannot measure a cylindrical or oblong taper to a very high accuracy (20 millionths of an inch) is incorrect.

The question really is what do you really need to measure so that your measurement gives you an insight into the condition and/or performance of the barrel being measured?

Great discussion.

Hope this helped and did not muddy things up.

Bob

 

[Reloadron]

I am not an expert at TE or MW gaging or the dynamics of the wear and/or erosion in these areas. I am, however pretty familiar with measuring all sorts of physical dimensions in an industrial and lab environment.

From the OP's post, it seems that he wants to measure the distance from the chamber of a 0.300" diameter datum. The idea being that the farther away from the chamber this datum moves, the more TE has occurred.

This is not measuring taper, which is the angle along a cone-shaped surface from a cylinder. Typically we take two diameter measurements a known distance apart and derive the angle from that.

I don't assume that TE will produce a straight cone-shaped erosion pattern, so taper is really not what we should be concerned with.

Does it matter from an accuracy standpoint how large the bore has eroded near the chamber, or is the intent only to see how far down the bore the ID is larger than 0.300"?

The idea that one cannot measure a cylindrical or oblong taper to a very high accuracy (20 millionths of an inch) is incorrect.

The question really is what do you really need to measure so that your measurement gives you an insight into the condition and/or performance of the barrel being measured?

Great discussion.

Hope this helped and did not muddy things up.

Bob

Hi Ya Bob, you make some very interesting and valid points. I think across the board a few hings need understood. You are correct in that the erosion taking place in front of the cartridge mouth is not uniform and that looking or measuring from a breech face to the 0.300" point in a chamber will not tell us the size of the cone. The only thing a muzzle erosion gauge tells us is when a barrel exceeds a certain number (we seem to like 5) it should likely be replaced. However, I have seen plenty of guns that shoot just fine at a reading of 5. Matter of fact since a barrel has an entrance and exit I would be more concerned with what is going on at the exit.

Doing as Guffy suggested here are a few examples of using a gauge.

First, some basic gauges including a gauge for M1 Garand 30-06 Springfield only followed by a gauge which uses inserts for M1 Garand 30-06 and M1A/M14 or M1 Garand using 308 Winchester.

Throat erosion reading and yes, that is a crack in the birch rear handguard.

Now moving along to the muzzle end and an example of a pretty worn muzzle.

Blackened with a marker we insert the gauge (Tapered End) into the muzzle.

Finally we measure to the line or markings in the black where the gauge stopped.

A much better choice of measuring tool would be a "Blade Micrometer" however, we ran with what we had and is good enough. With about a .507" reading the muzzle is not the best or shows about 0.005" of wear. Also, worth noting is the wear is not uniform meaning that inside the muzzle, at the exit we have an egg shaped barrel and this is where accuracy really suffers. The barrel used for the latter images is an old take off.

I regret that before I retired I never dragged a few old barrels into the machine shop and milled a few to clearly reflect ME and TE.

Ron

 

[fguffey]

From the OP's post, it seems that he wants to measure the distance from the chamber of a 0.300" diameter datum. The idea being that the farther away from the chamber this datum moves, the more TE has occurred.

A gage can be made to measure the length of the erosion, it is not my job to convince anyone it can be done. I did ask the OP if he was interested in contacting me off line. Back to measuring the taper, the length of the taper would be nothing more than something that would be nice to know.

the farther away from the chamber this datum moves, the more TE has occurred.

And the larger the diameter of the bore at the beginning of the rifling; it is relative.

The throat erosion gage has its own pilot. Centering, wiggling and wobbling are not things the user has to get into mortal combat with.

F. Guffey

 

[fguffey]

The idea that one cannot measure a cylindrical or oblong taper to a very high accuracy (20 millionths of an inch) is incorrect.

I did not say “no one”, I can but for the life of me I can not think of a good reason for doing it; there is another way.

(and there is another way) Again, there is chamber casting, at last count there were two shooters,r eloaders etc. that know how to cast a chamber.

F. Guffey

 

[Reloadron]

I did not say “no one”, I can but for the life of me I can not think of a good reason for doing it; there is another way.

(and there is another way) Again, there is chamber casting, at last count there were two shooters,r eloaders etc. that know how to cast a chamber.

F. Guffey

Maybe a recount is in order. You are not the only member with a machinist or tool and die background. Maybe by your count? Many of us have and know how to correctly use Cerosafe Chamber Casting Alloy. Additionally, many of us have the ability to post material the average person asking a simple question can grasp.

Ron

 

[M100C]

All,
Thanks for the posts. I guess maybe I was making this harder than I had intended. I'll give this a second go!

Here is a picture of an example gauge graduated for MW on the front (right) and TE (left, towards the handle):

My MW gauge has a knurled handle (which would be between the MW and TE graduated marks on the gauge shown).

Since the MW portion of the shown gauge comes "to rest" in the throat while reading the TE scale, then by measuring from the end of my gauge, I can determine where it would be on the shown scale, and thus the TE reading.

In short, if someone had this gauge, and provided the inches/graduation for both scales, and distance between them (i.e. from 10 on MW scale to 1 on TE scale), I'd be set.

Jim K, rcmodel, Reloadron,
Thanks for the additional information. I always get something from your posts, and I appreciate you sharing your knowledge on this forum.

 

[fguffey]

Post 4:

In addition to Jim's fine description this is a good read and explains the numbers with a few dimensions. Jim also makes a good point where they refer to TE (Throat Erosion) and ME (Muzzle Erosion) but in reality the muzzle shows wear and not really erosion.

And then there is post 14:

Had you had posted #14 ahead of post #2 it would not have been necessary for me to get involved. I knew when I started no one knew what a taper gage was and how it is used. Then there is that part about ‘what’ it measures. A taper gage is a hole gage.

A recount; I have watched threads about chamber casting knowing if I got involved it would not end well. And then one day on another forum a shooter/reloader joined the forum for the sole purpose of learning how to case a chamber. I did not get involved until members started taking liberties, they started making insults etc.

I apologized for the forum’s bad behavior and had him contact me. It was not long before he had cast the chamber in all of his rifles. The M1 was his biggest challenge. He did not need a lot of help and had he remained a member of the forum the forum would have benefited. He could not believe how desperate forum members were for attention.

I am not desperate for attention; the former member of ‘another forum’ has the ability to case a chamber; that make two.

F. Guffey

 

[fguffey]

Jim K, rcmodel, Reloadron,
Thanks

Again, the tapered gage requires a pilot; there are a few shooters that get nervous when something is shoved into the muzzle that is not muzzle friendly.

Then there is the bent handle; if you are going to reinvent the tapered gage why not make it a two ended gage. You could go with 270 cal. on one end and 30 cal. on the other.

F. Guffey

 

[M100C]

fguffey,
You go involved because I used the word 'wringing'.

I would not have got involved but you said ‘wringing’.

I am still not sure why 'wringing' caused you to engage. Getting involved wasn't necessary from my perspective, but I appreciate the varied other topics in your posts.

Then there is the bent handle; if you are going to reinvent...

Not reinventing anything; no intent to. Just making a central point: If the same taper, graduated to read muzzle wear, is inserted deep enough to allow one to read throat erosion on the same gauge, then there must be a fixed relationship between the marks on both ends. Knowing this relationship, I can estimate TE with my MW gauge.

I apologized for the forum’s bad behavior and had him contact me. It was not long before he had cast the chamber in all of his rifles. The M1 was his biggest challenge. He did not need a lot of help and had he remained a member of the forum the forum would have benefited. He could not believe how desperate forum members were for attention.

I am not desperate for attention; the former member of ‘another forum’ has the ability to case a chamber; that make two.

So, because you have that ability, and taught the former member how to cast a chamber, that makes just you two, huh? No one else here?

 

[nofishbob]

I knew when I started no one knew what a taper gage was and how it is used. Then there is that part about ‘what’ it measures. A taper gage is a hole gage.

Respectfully, Mr Guffey, I do indeed know what taper gages are and how they are typically applied in industry and research. I also know that a taper gage is not a hole gage.

Taper is expressed as an angle. You need two diameters measured a known distance apart to derive the taper angle of a bore or a spindle.

When you are evaluating MW or TE by jamming a tapered or stepped gage into the barrel and noting how far in you can insert it, you may get useful information, but this is not a taper gage, and you are not measuring taper.

I don't believe that it is actually desirable to measure the taper angle in this application, as geometrically, taper angle would not be a very good way to describe or compare the degree of MW or TE.

Hope this is more clear than my last post.

Bob

 

[fguffey]

Taper is expressed as an angle. You need two diameters measured a known distance apart to derive the taper angle of a bore or a spindle.

I will assume I have the luxury to disagree. The op is trying to measure the length of the taper. That can not be done with a fixed gage. The throat erosion gage is a fixed gage with a greater taper than throat erosion. When the throat erosion gage stops it stops against the hole/bore. In a few circles that would be considered interference fit.

‘Wringing’

I thought that was something I would do and thought I could help, I only know on one other person use that term on a reloading forum. Now I will assume we are talking about two different uses of the word 'wringing'.

When you are evaluating MW or TE by jamming a tapered or stepped gage into the barrel and noting how far in you can insert it, you may get useful information, but this is not a taper gage, and you are not measuring taper

.

Back to the beginning, the OP wants to measure the length of the taper. The throat erosion gage does not measure the length of the taper and it does not measure the angle of the taper because the taper is greater on the gage than the taper of the throat erosion.

Back to 'wringing', I can measure the length of the taper, when the OP threw in the word 'wringing' I thought he could. This reminds me of the problem a reloader has when measuring the diameter of the case, the case is tapered and more like a spindle.

F. Guffey

 

[M100C]

fguffey,
Thanks for the post; that helps me understand your thinking. At the time of your first post, I did not yet know you had a background as a machinist and in the T&D industry. We are talking the same thing.

All through college, I worked in a machine shop, building racing engines; mostly BBC and Pontiac. To make sure our micrometers were reading correctly, from time to time, I would wring together gauge blocks to assure accurate OD measurements. As I am sure you know, just stacking the blocks will trap a film/voids between the blocks; this would cause them to slide off one another and worse - lead to incorrect readings. Then, if we calibrated the micrometer this way, it would propogate the error across the range. By contrast, if one wrings them together, it causes surface tension and minimizes film thickness and contaminants on the face of the block, and the blocks will "stick".

I oriented the M1 barrel plumb, and the back end of my MW gauge is machined (though not like a gauge block). Using what I had, I wrung together gauge blocks, and stacked them atop the back of the MW gauge (seated in the throat) until they formed a plane with the face of the chamber.