Mini Treatise On Barrel Markings

[darrylta]

TD,

Please check your crystal ball, there's a difference between from a Savage and on a Savage.

My statements are my opinions, I'm not writing a historical thesis.

Lighten up will ya,

-Darryl

[reconbob]

For the record and the curious here is what the U.S. Ordnance (these drawings were

obtained by me from U.S. Government/Rock Island Arsenal via Freedom of Information

Act back in the late 1970's) drawings say about the drawline. Sorry the pics are a little fuzzy

but since its a flat sheet of paper my camera had trouble with depth/auto focus)...

 

Here is the barrel:

 

http://i51.photobucket.com/albums/f392/reconbob/IMG_2826.jpg

 

And the receiver:

 

http://i51.photobucket.com/albums/f392/reconbob/IMG_2829.jpg

 

Bob

[Arthur Fliegenheimer]

According to Doug Richardson's Thompson Technical Volume 1 (p. 25):

 

 

 

Its purpose is to enable any barrel to screw on to any receiver such that when properly tightened, the front sight is is positioned at the top of the barrel. This is important for guns which have the sight pre-machined on the barrel. It may have been that the Thompson front sights were fitted on the barrels before the barrels were fitted to the receiver. If so, the witness marks [scribed on the side of the receivers] make some sense. When the M1/M1A1 models were introduced, the system of qualified threads was abandoned. ...

 

This theory is getting or losing traction?

 

 

 

Bob,

 

Well said. I agree that the witness/index/draw marks (whatever ones chooses to call them) doesn't always mean the gun has been rebarreled but I have never seen a Colt Thompson with an original barrel where the lines didn't match. All original WWII guns observed also line up.

 

Chuck,

Do you include those that AOC changed out for the 1932 Cutts as original barrels? By match, do you mean with zero error above or below the line like here:

 

http://i17.photobucket.com/albums/b56/Polythemus/Colt1921A129barrelmark.gif

 

There does seem to be some evidence that a barrel might have had the drawline added after installation as seen here on this Colt Navy #2101 with British proofs as the line is shorter....

.

 

http://i17.photobucket.com/albums/b56/Polythemus/bm_barrel.jpg

 

As compared to the drawline on this Colt 1921 #5316

 

http://i17.photobucket.com/albums/b56/Polythemus/DSC_1893_01.jpg

 

 

 

...

Edited March 31, 2012 by Arthur Fliegenheimer

[gijive]

Arthur,

 

Good pictures. I am referring lines that aren't off over a quarter of an inch like I have observed on some of the parts kits. I would consider the rebarreled Colts with the Type II compensator as original barrels and they seem to line up from what I have seen. Have you observed examples of these rebarreled Colts with draw lines not matching? Your second pictures of the Colt with the British proofs does look like it was added after the barrel was on.

[Arthur Fliegenheimer]

Arthur,

 

Good pictures. I am referring lines that aren't off over a quarter of an inch like I have observed on some of the parts kits. I would consider the rebarreled Colts with the Type II compensator as original barrels and they seem to line up from what I have seen. Have you observed examples of these rebarreled Colts with draw lines not matching? Your second pictures of the Colt with the British proofs does look like it was added after the barrel was on.

 

Chuck,

If the caveat about "lining up" is not more out of line than 1/4 inch, I have not seen Colt TSMGs, with what we agree on as original barrels, that are out of this standard. Here is a Colt drawline that is a scosh under the receiver drawline.

 

http://i17.photobucket.com/albums/b56/Polythemus/ColtNavy14355drawmarkcu.jpg

 

 

I agree about the British proof Colt barrel. This is why it is imperative to be skeptical about the originality of a barrel just because there is a perfectly lined up drawline of barrel and receiver, and conversely, just because it doesn't perfectly line up doesn't mean it isn't original. Although, the barrel drawline on the British Colt barrel doesn't resemble a Colt/Remington/AOC drawline.

Edited March 31, 2012 by Arthur Fliegenheimer

[reconbob]

I think the drawline theory that Doug describes has no traction. The theory, as stated,

is a good description of why you might go to the trouble to have drawlines. But in the real

world, I know of no ordnance procedure anywhere, at any time, that advocated removing

a serviceable barrel from one gun, and then later fitting it to another. If the barrel was serviceable

you left it on. Perhaps in the very few cases where a receiver was damaged you might remove

the barrel for use on another gun, but this would be a rare occurence.

There was always a good supply of new barrels to replace used/worn/damaged ones. In an "Enemy At The Gates" scenario you might do this. One big reason for not re-using barrels

is that if you take a barrel off and re-fit it with the same torque it will screw on a little farther and

the sights will be off.

In our small selection of barrel photos we have seen quite a variance. We see drawlines exactly

matching ranging to more than 1/4" off.

Clearly authenticating a barrel is an art, not a science. For me the big question is - are the barrels

we see on some of the Russian front ends with the drawline 1/4" off and no S original, or were they

replacement barrels installed during WW2?

 

Bob

Edited March 31, 2012 by reconbob

[winbar]

As a hobbyist, I have re-barreled 2 registered B.A.Rs. and was very thankful for drawmarks. Is it possible that the draw lines were also required to aid armorers in case they had to replace grip mounts that were sprung (especially with the vertical foregrip) in hard use?

Doug

[reconbob]

Do not misunderstand - the drawline is essential for M1903, M1903A3, M1917, BAR,

Garand (the flats), M1 & M2 carbine etc. But these guns all have permanently attached

sight bases (never intended to be removed), or gas ports, or extractor cutouts and you

needed the drawline to install them properly.

But Thompson barrels don't have sights put on until after they are on the gun. The

absence of compensator and ring sight pin holes and cuts on the barrel for the pins

proves this. So there was no reason for a drawline.

 

Bob

[gijive]

For me the big question is - are the barrels

we see on some of the Russian front ends with the drawline 1/4" off and no S original, or were they

replacement barrels installed during WW2?

 

Bob

 

Bob,

 

This is what always made me suspect that these Russain Lend-Lease kits may have been rebuilt in WWII prior to shipment. That clue alone doesn't prove the theory, but coupled with all the rebuilt butt stocks it may at least point in that direction.

[giantpanda4]

But Thompson barrels don't have sights put on until after they are on the gun. The

absence of compensator and ring sight pin holes and cuts on the barrel for the pins

proves this. So there was no reason for a drawline.

 

Bob

 

Bob,I do not see this - do we have original WWII barrels, not replacement ones, that are not drilled for the sight pin? Do you have the drawings for the barrels? Or only the replacement barrels that are out there? This theory is 180 degrees from Richardson?

[Arthur Fliegenheimer]

But Thompson barrels don't have sights put on until after they are on the gun. The

absence of compensator and ring sight pin holes and cuts on the barrel for the pins

proves this. So there was no reason for a drawline.

 

Bob

 

Was DR speaking generally about the TSMG, or about the Colt TSMG specifically?

 

There are no drawlines on the receiver and barrels of the AOC Annihilator versions or Model 1919, or #45 MODEL 1921. The idea of the function of the front sight pin is twofold? It is not only required to keep the pressed on ring sight/Cutts/ screw on ring sight from loosening, but to allow for minor sight aligning adjustments of the sight while on the barrel and mounted on receiver before drilling the hole for the pin to secure it in place?

Since the original sight on the 1921 was pressed on, it would be easier to affix it to the barrel for alignment purposes after the barrel was mounted on the receiver. But is that true for the screwed on sights when they came on the scene in 1926? Did AOC/Colt thread the end of the barrel for the new Cutts while it was on the receiver or was the barrel first removed for the threading and addition of the Cutts

Edited April 1, 2012 by Arthur Fliegenheimer

[TD.]

So there was no reason for a drawline.

Agree, but Colt’s, Savage and Auto-Ordnance Bridgeport continued on marking at least some barrels with draw lines. The ordnance drawing you posted, the AOC Qualifying Gauge and the end product (barrels) prove draw lines were a common occurrence. The question is why all of these companies continued on this path for so many years when everyone agrees draw lines do not work.

 

Is it possible the draw lines do work with Colt barrels and receivers? Forget the WWII production for a moment and concentrate with only the Colt era. I have always heard when changing a barrel on a Colt Thompson with another Colt barrel the draw line will not align correctly and the front sight (which is usually installed on the substitute Colt barrel) will not align. But I have no actual experience in this area. Who has some experience in this area they would be willing to share? Who has some genuine Colt receiver fronts and genuine Colt barrels taken from cut-up Form 10 guns? Genuine ringed Colt barrels would work perfectly for this test.

 

Did AOC/Colt thread the end of the barrel for the new Cutts while it was on the receiver or was the barrel first removed for the threading and addition of the Cutts

Excellent question. Bob’s knowledge of the available machinery to perform this task may provide an answer to this question. Given the machinery available from 1926 to 1940, could the barrel boss be threaded while the barrel was on the receiver? Or would the barrel have to be removed? If either way, which would be easier for threading purposes? Remember, the pinned front sight was removed and the boss was first turned down to remove the slot cut for the front sight pin; then the boss was threaded. At least, that is how it has been reported. And given the small diameter of the Type I compensator, it does appear that is what happened.

[winbar]

I believe David (dalbert) has a copy of the Combat Bookshelf- Thompson Submachine Guns Five Complete Manuals. (Maybe he has a scanner,I don't.)The last manual is the 1936 Auto-Ordnance Corporation law enforcement catalog.

Page 28 is an ad for the Cutts Compensator. The last paragraph says,"Cutts Compensators can only be fitted to Thompson Carbines and Submachine Guns at the factory."

The price list on page 29 says,

"Cutts Compensator fitted to Thompson Gun barrel at factory ---(barrel extra)....$25.00"

Doug

[Arthur Fliegenheimer]

"Cutts Compensators can only be fitted to Thompson Carbines and Submachine Guns at the factory."

 

Indeed. But this advisory does not shed light on whether the barrel was removed or stayed in place for this procedure. Either scenario would require the services of the factory.

[reconbob]

If I was to guess - and of course there is no way of knowing - I would say that

to put a comp on a M1921A

they chucked up the barreled receiver in a lathe and turned the end down, then

threaded it by hand with a die. That would beat the heck out of barrel off and on.

While we're at it, here is a M1921 Colt barrel screwed into the front of receiver

AO 50539 - this is perfect - by torquing it on until the lines line up you'd have the

right fit:

 

http://i51.photobucket.com/albums/f392/reconbob/IMG_2834.jpg

 

Here is the same barrel screwed into the front of receiver 294314 which we would

figure to be Savage - the drawline is even father off than what we see on some of

the Russian kits:

 

http://i51.photobucket.com/albums/f392/reconbob/IMG_2833.jpg

 

But, if this barrel was torqued on the gap would be the same as what we see on some

of the Russian kits...so maybe the

same tooling was used to mark the barrels and when fitted to Savage receivers you get the gap?

 

Bob

Edited April 1, 2012 by reconbob

[buzz]

Great thread.

 

The draw mark controversy leads to a few basic questions (in my mind anyway)

 

1. Would a draw line be used for torqueing down a barrel properly?

 

To me the obvious answer is NO, it would NOT have anything to do with torqueing the barrel on tight enough.

 

When you install threaded parts to the correct tightness, you use either a torque wrench or a turn-of-the-wrench method.

 

To use an index mark for torqueing a barrel on would be a ridiculously complicated and expensive way of doing a very simple job.

 

So obviously, the index mark on the barrel would be for alignment purposes only.

 

2. So that leads to the second question - What needs to be aligned?

 

Neither the barrel or the front sight need to be indexed to the receiver as the barrel is tightened on.

 

The barrel doesn't need to be aligned and the front sight could easily be adjusted after the barrel was installed.

 

The chamber doesn't need to be aligned since the bolt doesn't do anything more precise than smack into the rear of the barrel.

 

3. Suppose that the mark was applied after the barrel was installed? What purpose would that serve?

 

The barrels weren't removed except for replacement, so the mark would not be required for any normal use or maintenance on the gun.

 

 

This subject is mysterious.

 

On some guns the marks are lined up perfectly.

 

On some they are off a little or a lot, and some they are missing entirely. Apparently sometimes they were applied after installation.

 

Some posters have said this means the barrels are not original.

 

But nobody has actually come up with any sensible reason for having the mark at all.

 

 

Suppose you bought a NOS barrel to put onto your Thompson and it had no index mark.

 

You would spin the barrel onto your receiver, tighten it with a wrench.

 

Then you'd spin on the front sight, align it and pin it.

 

At no point would you say, "Gee I wish this barrel had a draw mark on it so I can install it properly."

Edited April 5, 2014 by buzz

[reconbob]

The original ordnance drawing for the M1928A1 barrel (D35509) specifies that a draw line be marked on the

barrel and that it must match a thread qualifying gage. However, there is no mention of a drawing number for the

gage. There is no mention of fitting a compensator to the barrel, or for machining a groove in the end of the barrel

to accept a future compensator/sight pin.

I do not have a drawing for a compensator, but I do have the drawing for the ring sight (A153066) and it specifies

that the front sight pin hole be drilled at assembly, not when the sight itself is made.

I think that when the gun was put into production that - out of habit - the draw line was used. All of the companies

and engineers involved had been making commercial firearms, and just about any commercial barrel from a pistol

up to a rifle had a draw line because of the necessity of lining up fixed sights or sight bases. Then time

goes by and everybody realizes that the draw line is not really needed because there is no sight on the barrel. Now,

maybe it was the procedure to fit compensators to barrels in a precise position and then later fit those assemblies

to receivers. But then again, maybe not. I do not believe any of us have ever seen a true MINT-in-the -wrapper barrel

with a compensator or a ring sight on it. Plus, the compensator and sight when they are new are not yet drilled for

the sight pin.

All we have is theories. we don't have any photos or manuals from the factory production addressing this. I think

the evidence of new original parts and drawings indicates that the draw mark was put on the barrel, but that the comp

or sight was not fitted to the barrel until the gun was assembled. If it was otherwise we would have seen spare barrel

assemblies with comps and sights on them. A MINT original barrel will not yet be drilled for the sight pin, and a MINT

original comp or ring sight will also not yet be drilled for the pin.

 

Bob

[buzz]

That certainly sounds reasonable.

 

I am a structural engineer, you'd be surprised how many things we do for government agencies simply because some guy in 1955 thought it was a good idea and wrote something into the design manual.

 

The present day government people who are administering the contracts do not understand engineering well enough to evaluate their own specs.

 

One time I did a design, and the client freaked out when they saw my calculations.

 

Turned out that I was basically the first person who ever did the calculation correctly, they were not used to seeing the correct method used.

 

I actually had to write them a long memo explaining how their own design specs worked.

Edited April 5, 2014 by buzz

[reconbob]

Say, you may be just the guy to crunch the numbers for the recoil ballistic pendulum...

 

Bob

[buzz]

You know what would be a very telling clue?

 

If they dropped the use of the draw marks on the guns at any point. Like on the wartime production guns or M1s and M1A1s.

 

That would show that the marks had been some sort of leftover that got ditched.

 

Also, I cannot help but note that putting the draw marks on would be a very cheap operation.

 

It might have been easier initially to simply bang the line onto the guns than to trim the requirement out of the specs.

 

 

I think the fact that the line on the barrel is missing on a lot of finished guns and spare barrels is very revealing: if the marks were not needed for one gun, then they weren't needed for any gun.

[buzz]

Say, you may be just the guy to crunch the numbers for the recoil ballistic pendulum...

 

Bob

I would be glad to help out

 

You're not going to need much help, it's a very simple device from a physics standpoint.

[anjong-ni]

I don't have any books that show the Thompson production sequence, but I would imagine that the barrel was installed into its receiver and tightened.... twice.

The receivers have a "scribe line" on the right side.

The barrel was "torqued" into the receiver.

Then a pencil line was scribed onto the barrel in line with the "scribe line" on the receiver.

Then the barrel was removed from its receiver.

The pencil line was "chiseled" horizontally into the barrel flange in a fixture.

The barrel went into a sight installation jig.

With the chisel mark aligned upward in the fixture, the front sight was pressed on in perfect 90 degree alignment.

The barrel and sight assembly then went to a further fixture where it was drilled and pinned.

The barrel was then re-installed on its receiver and tightened to the alignment of the scribe/chisel mark.

 

- I believe that M1s used a centerpunch mark on barrel and receiver, but same idea.

-Ordnance qualified threads aren't perfect enough to account for the thousands of perfectly aligned barrel/receivers.

-The "imperfect" known-to-be-original guns could have been made off the assembly line of originally lost, misplaced or rejected parts.

-Although the scribe marks don't align on imperfect guns, the sights are vertical and the barrels haven't been drilled twice, correct?...Phil

[buzz]

Why would you need to drill and pin the compensator with the barrel removed from the receiver?

 

What purpose is served?

 

You don't need to chuck the breech end of the barrel into a lathe or vice.

 

Why not just leave the receiver in place on the end of the barrel?

 

What about all the guns that don't have the mark on the barrel?

 

Something doesn't compute.

 

Screwing and unscrewing barrels would be one of the major assembly operations on the gun, why do it twice?

[anjong-ni]

Well, why indeed do it twice? I'd offer, again,

-The "scribed draw line" or "center-punch" on the receiver is done at manufacture.

-The "chisel mark" or "center-punch" on the barrel was performed while it was NOT attached to the receiver.

-Known-original guns with components that are unmarked or poorly aligned are probably "off-line" assembly of parts that were originally lost, rejected or misplaced in the que.

 

As ReCon Bob has demonstrated, ordnance qualified threads are not specific-enough to guarantee that "random" pre-marked receivers/barrels would line up when correctly torqued.

Yet, as we see, "most" of the barrel/receivers DO align perfectly with their marks. As do their sights, at a perfect 90 degrees..

I'm sure that the factory didn't waste any time or motion. While the barrel was off the receiver being "sighted", some other process step was probably being done to the receiver.

 

Just my guess. I work in mass production. We're always trying to "speed it up".

It's fun to wonder how they did it!...Phil

[buzz]

anjong-ni,

 

I'm not trying to nitpick or anything like that, but your theory about removing the barrel to put the front sight on just doesn't compute.

 

1. The barrel would be loose (maybe).

 

If this was a normal gun with witness marks on it, the barrel would be fitted up by hand snug to the receiver, then the shoulder of the barrel would be shaved a little on a lathe until the witness lines were a certain distance apart (give or take), then the barrel would be turned with a wrench until the marks lined up.

 

Then you'd be done.

 

But note that when you install the barrel, the threads stretch and the barrel and receiver deform a little.

 

So when you installed the same barrel again, it wouldn't be as tight.

 

 

2. Guns that actually need witness marks only have the barrel installed one time.

 

If a gun that actually needs witness marks only has the barrel installed once, why would they do a complicated double installation on a gun that doesn't need witness marks at all?

 

 

3. Most of the barrels were made with the marks already in place.

 

You can see that lots and lots of new-in-the-wrap barrels already had the mark so that sort of negates the whole double-install theory anyway.

 

 

4. Removing a barrel can be a difficult operation.

 

Sometimes you actually have to saw a relief cut on a barrel shoulder to get it off without warping the receiver. It's not always a gentle operation.

 

 

5. Not all thompsons have the witness mark on the barrel.

 

So why would some need this double-installation of the barrel and some not need any draw marks at all?

 

 

 

6. If they actually removed the barrel, why would the barrel draw mark be neatly machined onto the barrel instead of just struck with a chisel when the gun is still assembled?

Edited May 18, 2014 by buzz