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Replacement Barrel Proof Marks


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Looking at the NOS barrel that Bridgeport28A1 has for sale, I believe that you can tell a replacement barrel from an original by the placement of the proof P. The replacement barrels that I have seen have the P stamped so that it is readable from the muzzle. Original barrels have the P stamped so it is readable from the breach. The P will also be at top dead center and should have a punch mark on the P. Finally, the P on Savage guns is non-serif and the P on AOC guns is serif. Has anyone else noticed these things?

 

Dan

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I always assumed that the P was right side up if you were reading it while you were

holding the gun as if you were going to shoot it. So I guess that would be from the breech.

So, I go grab a few MINT G.I. barrels. One has a breech P, one has a muzzle P and one

has no P, or a P that is so poorly marked that you can't tell it is a P.

A replacement barrel will not have the punch mark inside the P until it has been fitted to

a gun and test fired. Since the P is applied to the barrel before the barrel is fitted to a gun

it is unlikely that when fitted to a gun it will be exactly at top dead center.

So I guess no hard and fast rule....

 

Bob

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I always assumed that the P was right side up if you were reading it while you were

holding the gun as if you were going to shoot it. So I guess that would be from the breech.

So, I go grab a few MINT G.I. barrels. One has a breech P, one has a muzzle P and one

has no P, or a P that is so poorly marked that you can't tell it is a P.

A replacement barrel will not have the punch mark inside the P until it has been fitted to

a gun and test fired. Since the P is applied to the barrel before the barrel is fitted to a gun

it is unlikely that when fitted to a gun it will be exactly at top dead center.

So I guess no hard and fast rule....

 

Bob

Very interesting, especially the New GI replacement barrels. I only have a few and have seen a few in pictures.

 

What about being cross drilled for the front sight/compensator cross pin?

Edited by DZelenka
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I always assumed that the P was right side up if you were reading it while you were

holding the gun as if you were going to shoot it. So I guess that would be from the breech.

So, I go grab a few MINT G.I. barrels. One has a breech P, one has a muzzle P and one

has no P, or a P that is so poorly marked that you can't tell it is a P.

A replacement barrel will not have the punch mark inside the P until it has been fitted to

a gun and test fired. Since the P is applied to the barrel before the barrel is fitted to a gun

it is unlikely that when fitted to a gun it will be exactly at top dead center.

So I guess no hard and fast rule....

 

Bob

The replacement barrels you checked, were they all Savage or were there a mix of manufacturers? Did the direction of the P correspond with any particular manufacturer?

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I am curious to know if there is any documentation out there to support these statements. I am still not 100% sold on this. Does anyone have any solid or at least good data to back this up? The barrel I have might not be NOS, but from what I see it looks to fit the bill. I might clean all the cosmoline off of it at this point to see. Thanks for any information that can back all this.

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Dan - Checked 10 MINT barrels:

 

Stevens (square S) poorly marked/not legible P - 1

Stevens P upside down when viewed from rear as you would hold gun - 3

Savage (round S) P right side up when viewed from rear as you would hold gun - 1

Savage P upside down when viewed from rear as you would hold gun - 6

 

Bob

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Dan - Checked 10 MINT barrels:

 

Stevens (square S) poorly marked/not legible P - 1

Stevens P upside down when viewed from rear as you would hold gun - 3

Savage (round S) P right side up when viewed from rear as you would hold gun - 1

Savage P upside down when viewed from rear as you would hold gun - 6

 

Bob

So, 10% with the P right side up? Very interesting. What kind of barrels are they? 1928? Smooth or finned? M1? I assume that none of these are drilled for the cross pin?

 

Have you ever seen a gun with a known original barrel with the P upside down?

 

Thank you for checking your barrel stock. I wonder what the story was with that one barrel. Was it intended to be installed on a gun and just randomly ended up being a replacement part? Were the ones with the upside-down Ps always destined to be replacements? We will likely never know.

 

Dan

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They are all M1/M1A1 smooth barrels from Doug Richardson. There are many

more but I really don't have time to go off and do a barrel study. None have the cutout

from the cross pin...BUT...

 

One of Doug's items was that he took what he said were "new WW2 surplus barrels"

and machined the thin M1921 style fins on them. (Listed in his catalog circa 2017 for

$430) and every one of them has the cutout for the cross pin. No idea why.

 

Bob

 

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I am the one with the barrel that claimed that it is NOS, but I spent two hours cleaning off the cosmoline and I would have to agree it is not NOS and along with that I found traces of pitting on the barrel, but I still have some concerns about the barrels not being fired at the factory. Is this a possibility? The bore in the barrel however is flawless and looks perfect to me. I mean I know there are so many variations of these barrels, but I am trying to get some sort of fact to back the statements made. I understand there are some barrels out there that are actually NOS and you have some sellers who are masking there barrel as a NOS by dipping it in cosmoline, which I find to be very horrible and bad practice as I want to make sure I know what I have before I attempt to sell it. Thank you for all your help.

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If its an original military barrel (spare part) it is proof fired and marked with a P as we have seen.

This is so it is not necessary for an armorer to have to proof fire a gun when it is rebarreled.

 

Commercial/after market barrels - and there are many out there - are not test/proof fired and

are just sold as-is.

 

Bob

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I am the one with the barrel that claimed that it is NOS, but I spent two hours cleaning off the cosmoline and I would have to agree it is not NOS and along with that I found traces of pitting on the barrel, but I still have some concerns about the barrels not being fired at the factory. Is this a possibility? The bore in the barrel however is flawless and looks perfect to me. I mean I know there are so many variations of these barrels, but I am trying to get some sort of fact to back the statements made. I understand there are some barrels out there that are actually NOS and you have some sellers who are masking there barrel as a NOS by dipping it in cosmoline, which I find to be very horrible and bad practice as I want to make sure I know what I have before I attempt to sell it. Thank you for all your help.

There are actually two barrels for sale on here. Bridgeport28A1's barrel is the one that originally got me to thinking. I provided my observations. Bob provided his. Unfortunately, there really doesn't seem to be enough data to reach any definitive conclusions. I have only been playing with Thompsons for about 5 years, but in that time I have looked at a number of guns and a LOT of pictures. I have come to a few conclusions about the way the various factories did things. I was fairly sure I was right about the direction the proof P was applied on original and replacement barrels. Bob found an example that calls that observation into question. There are other things I have noticed. Proof Ps on Savage barrels use a non-serif letter. AOC uses a serif. Punch marks on a Savage receiver are in the center, AOC on the top left. Rivets on Savage rear sights are flat, AOCs have a dimple. These things are much like the direction that US Property faces on M1s and the Full Auto lettering which are manufacturing differences.

 

Dan

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