The U.S. Caliber .30 Carbines - Barrel Manufacturers

The U.S. Carbine Caliber .30

Barrel Group






Trigger Housing

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        Gas Piston
        Gas Piston Nut

Barrel Characteristics

The U.S. Carbine Caliber .30
Barrel Characteristics
Lands & Groves: 4
Rifling: 1 right hand turn in 20 inches
Rifling Method: Broach or Button
Gas Cylinder: Integral or Swaged
Original Finish: Blued or Parkerized
*measured from the muzzle to the end of the skirt

Lands & Grooves

All .30 Caliber Carbine barrels manufactured under contract to the U.S. Government have 4 lands and grooves.

4 lands and grooves, shown from chamber end of the barrel

Gas Cylinders

Gas cylinders were manufactured by one of two methods. The gas cylinder was machined integral with
the barrel (top) or machined as a separate part then compressed (swaged) onto the barrel (bottom).

Cut-away showing Swaged Gas Cylinder pressed onto barrel and gas port drilled through gas cylinder and barrel

Swaged gas cylinders were normally manufactured by the company who manufactured the barrel.
With the exception of Rock-Ola, prime contractors did not place their entire name on their
gas cylinders. Gas cylinders having the name Rock-Ola were used only on Rock-Ola barrels.

Inland manufactured their own gas cylinders, occasionally marked II or I-I. Inland also subcontracted a number of
companies to manufacture additional gas piston cylinders. The subcontractors were assigned different markings.

Gas Piston Cylinders
I-I, I I
Inland Subcontractor Markings
Gas Piston Cylinders
BI, B1
W.I., WI




Note: BI marked gas piston cylinders were manufactured by B & P Motor Company for Inland. Not to
be confused with BI marked barrels manufactured by Brown-Lipe-Chapin for Inland (see below).

Gas Piston and Gas Piston Nut

Arrows indicate openings for securely staking the gas piston nut to the gas cylinder

Left: Early Gas Piston Nut
Right: Later Gas Piston Nut, countersunk to allow more piston movement

Gas pistons remained unchanged throughout production. Gas pistons were unmarked
except by the subcontractors who manufactured them for Inland Mfg.

Inland Subcontractor Markings
Gas Pistons

Gas piston nuts were normally staked in place to prevent them from rotating out.

Chamber & Proper Headspace

Chamber with Proper Headspace

As with all firearms but particularly center-fire semi-auto firearms and particularly those made for use as military rifles, the distance between the face of the bolt and forward end of the chamber is critical. This distance is referred to as "headspace" and by design controls expansion of the casing and the gases generated when the weapon is fired.

When acquiring a used M1 Carbine the headspace should be checked before firing the weapon.

This can be done by a qualified gunsmith or by purchasing headspace gauges for the U.S. .30 Caliber Carbines, manufactured by several different companies and sold retail by most large gun supply retailers (Brownells, Cabelas, Midway).

Use of a headspace gauge is pretty simple and straight forward. The carbine is disassembled as is the bolt. The stripped bolt is placed within the receiver and slid to the rear. Each gauge is individually placed in the cleaned chamber, the bolt is then moved forward towards the breech until the bolt stops:

Headspace is specific to the bolt and barrel. If the bolt is replaced the headspace should be checked again. Sometimes when the barrel fails the "No Go" and "Field" Gauges, replacing the bolt may provide for proper headspace. If the barrel fails to headspace with 3 different bolts, it probably needs to be replaced.

Barrel Skirts

The first GI carbine barrels had what is called a "long skirt". This is an extension at the breech end of the barrel that surrounds the chamber from approximately the 10 o'clock position, downward and around to approximately the 3 o'clock position. The purpose of the skirt is to deflect the cartridges exiting the magazine into the barrel chamber. U.S. Army Ordnance decided the long skirt was not really necessary and approved the "short skirt" instead, which starts at about the 10 o'clock position, running downwards to approximately the 7 o'clock position. It's not uncommon for a long skirt to have been shortened to the dimensions of the short skirt.

Long Skirt (left) - Short Skirt (right)

Barrel length is measured from the rear edge of the skirt to the forward edge of the muzzle.

The Muzzle

Most barrels have a rounded muzzle, some barrels have a flat muzzle. The crown at the front of the barrel is the area
immediately surrounding the bore. It controls the smooth flow of gases as the bullet exits the barrel and therefore
accuracy. Some manufacturers rounded the edges at the front of barrel, a few cut them flat.

Front Sights are covered on the next page.

Counter-Bored to repair crown.
Note the outer edge of the muzzle

A bore gauge may be used to measure bore wear. A reading of 1 or less is close to the dimensions when the barrel was new.
It's generally accepted the tighter the bore the more accurate the barrel. Accuracy depends on a number of things and
more than a few carbine owners have found the amount of bore wear doesn't always relate to accuracy.

Some carbine owners use the bullet of a .30-06 cartridge to estimate bore wear, in lieu of a bore gauge. The shape
of the pointed nose 30-06 bullet is far more reliable than the shape of the round nose .30 caliber carbine bullet.

Barrel & Receiver Alignment

The threads on the breech end of the .30 Caliber Carbine barrel are timed to align with the threads in the front of the receiver so when the barrel is tightened onto the receiver the slide grooves in both the receiver and barrel line up properly. This also aligns the barrel skirt and gas piston properly. Barrels and receivers manufactured under contract to U.S. Army Ordnance have alignment marks to facilitate quick alignment of the barrel to the receiver.

Alinement marks on bottom of barrel and front of receiver serve as a
reference point from which to start proper alignment of the barrel and receiver.

Barrel Machining Finishes

Turned and ground smooth

Turned and unground

Barrel Manufacturers

During WWII

Barrels Manufactured
Prime Contractors

  • Winchester Repeating Arms
  • Inland Division of General Motors
  • Underwood Elliott Fisher Company
  • Rock-Ola Manufacturing Company
  • Saginaw of Saginaw, MI
  • International Business Machines

All barrel manufacturers under contract to U.S. Army Ordnance marked their barrels with either their name or manufacturers mark. The most common location for this marking was on top of the barrel approximately 2" from the muzzle. Markings used by some of the barrel manufacturers slightly varied over time. Many manufacturers placed the month and year the barrel was manufactured directly below the manufacturers mark. This practice varied over time with some barrels having only partial date markings and some having no date at all.


small W

PW proof

Inland Mfg Div.
General Motors



Saginaw S.G. Div.
General Motors

I.B.M. Corp.

Underwood barrels having a date of 10-49 are believed to have been an error. The serial numbers of
other Underwood carbines in the same serial number range indicated a date of 10-43.

Not every prime contractor possessed the machinery and skilled personnel to manufacture their own barrels.

Prime Contractors
who did not
Manufacture Barrels

  • Quality Hardware (359,666 M1 carbines)
  • National Postal Meter (413,017 M1 carbines)
  • Standard Products (247,160 M1 carbines)
  • Saginaw Grand Rapids (223,620 M1 carbines)
  • Irwin-Pedersen Arms (refer Saginaw Grand Rapids)

Quality Hardware was the first of these companies to become a prime contractor who would not manufacture barrels. Barrels were to be obtained from the other prime contractors who manufactured barrels. By the beginning of 1943 it had become clear barrels were quickly becoming a critical part requiring special management to keep production lines moving without having to temporarily shut down until more barrels arrived.

Quality Hardware's first month of production in February 1943 fell far short of scheduled carbine production due to a lack of barrels.

The Government Free Issue Barrel Program

Under the Government Free Issue Barrel Program prime contractors who manufactured barrels produced a percentage of extra barrels beyond their own needs for those who did not manufacture barrels. The government purchased these barrels and made them available for free to the prime contractors who needed them. For those who used them the price the government paid the prime contractor per carbine was adjusted to reflect the cost of the barrel the government provided.

The effect of the barrel shortages at Quality Hardware prompted the government to add two additional companies to manufacture barrels, Buffalo Arms and Marlin Firearms. The Brown-Lipe-Chapin Division of General Motors, subcontracted to manufacture barrels for Inland, also manufactured barrels for the program. These barrels were provided to Inland, who marked with Inland markings before providing them to the program.

The Carbine Industry Integration Committee, made up of representatives from each of the prime contractors, was tasked with closely monitoring barrel production and demands on a daily basis and initiating the logistics of getting barrels to where they were needed most. Early on the needs reached the point some prime contractors were only hours away from having to temporarily shut down their production lines while they waited for barrels to arrive.

As the program progressed through 1943 the barrel shortage waned. But the program experienced it's own set of significant problems when prime contractors found barrels made by others, while within ordnance specifications, were sometimes at the other end of the allowances provided by the specifications and wouldn't fit their receivers. The percentage of rejects presented a significant problem resulting in the time required to correct the issues or return the barrels to the manufacture for correction or replacement when the barrels were needed immediately. Barrels manufactured by Buffalo Arms and Marlin were considered to be of lower quality than those by others.

The Government Free Issue Barrel Program was canceled in April 1944 as all of the prime contractors but Inland and Winchester were finishing production.

The exact number of barrels provided and used via the program will never be known. Only part of the records have been found.

Buffalo Arms Company
Buffalo, NY

   Time Period:1943
   Manufacturers Mark:varied (see below)
(top of barrel, aft of front sight)
   Quantity Manufactured:155,605 (estimated)
   Barrels Manufactured for:government free issue barrel program
  • Quantity ordered were more than quantities delivered. Those delivered had a high percentage of rejects for various reasons.
  • Some rejects could be salvaged, some could not.

The markings used by Buffalo Arms varied almost from one month to the next.
The example shown above was but one of five or six variations. It's not uncommon for the markings to be off centered to one side
or the other, partially stamped as above or absent the date.

Marlin Firearms Company
New Haven, CT

   Time Period:1943
   Manufacturers Mark:Marlin
(top of barrel, aft of front sight)
   Quantity Manufactured:85,000-125,000 (estimated)
   Barrels Manufactured for:government free issue barrel program
  • Marlin stamped their name lengthwise along the barrel. Most, but not all, were absent a date.
  • A Marlin document after WWII claimed they had manufactured 125,000 carbine barrels. Other estimates have been much lower, possibly in part due to rejects.

Barrel manufactured by Marlin. Most, but not all, Marlin barrels were undated.

Brown-Lipe-Chapin Division
General Motors Corp.
Syracuse, NY

   Time Period:1943-1944
   Manufacturers Mark:Inland markings (top of barrel, aft of front sight)
BI on barrel flat
   Quantity Manufactured:unknown
   Barrels Manufactured for:subcontracted by/for Inland Mfg. &
government free issue barrel program

Brown-Lipe-Chapin barrels for both Inland Mfg and the government free issue barrel program
have the usual Inland markings on top of the barrel with the letters BI on the bottom
of the barrel between the gas piston and breech.

If BI is observed on front of the swaged gas cylinder, the gas cylinder was made by
B & P Motor Company for Inland Mfg., not Brown-Lipe-Chapin.

Barrel Manufacturers


Springfield Armory
Springfield, Massachusetts

   Time Period:1950-1954
   Manufacturers Mark:SA
(top of barrel, aft of front sight)
   Quantity Manufactured:454,761
   Barrels Manufactured for:replacement barrels
  • Many markings appear to have been stamped one letter at a time with poor alignment and/or uneven distances between each
  • Orientation of the markings may run lengthwise down the barrel, top of letters towards sight or upside down
  • Dates may be partial and located below or aside the SA letters
  • Some of original SA barrels had the Ordnance crossed cannons logo stamped on the barrel flat. Some of these do not have the SA markings on top of the barrel.


(upside down)

Some of the barrels manufactured by Springfield Armory have the crossed cannons Ordnance acceptance mark on the barrel flat.

Herlo Engineering Corporation

Hawthorne, California

   Time Period:1970-1974
   Manufacturers Mark:HC
(on flat between chamber & gas cylinder)
   Quantity Manufactured:70,000+
(none accepted by government)
   Barrels Manufactured for:replacement barrels

Herlo Engineering Corp. manufactured .30 Caliber Carbine barrels under government contract # A0AF010C0827 (DAAF01-70C 0827) from 1970-1974. Other government contracts awarded to Herlo in the 1960's and 1970's included parts for the M14 rifle, M16 rifle, M60 & M72 Machine Guns, and the Nike and Hawk missile systems.

All of the Herlo .30 Caliber Carbine barrels were rejected by the government due to numerous quality control problems. These included inconsistent rifling twist rates, improperly sized gas cylinders, inconsistent barrel diameter in the area of the front sight and chrome lined barrels with off spec chamber dimensions. Not all of the barrels had these problems but the percentage was sufficient to warrant the entire contract being rejected.

Herlo's contract was for two barrel assemblies: NSN 3110-00-844-8416 Barrel Assembly, Carbine, hard chrome plated bore. NSN 1005-00-555-7154 Barrel Assembly, Carbine (bore not hard chromed).

The contract was for the complete barrel assembly. Each was individually wrapped in protective
paper and placed within an outer wrap for protection during long term storage.

The outer wrap was labeled with the information on the contents.

Herlo barrels were marked on the bottom between the gas cylinder and chamber with the stock number preceded or followed by
the letters HC (for Herlo Corporation). The markings include the month and year of manufacture along with a lot number.

8448416 identifies this barrel as having a hard chrome plated bore.

Hard chrome Plating

A Los Angeles area surplus dealer purchased these barrels from Herlo about 1975. Many, if not most, of the barrels were sold to the government of South Korea with many imported back into the United States in the mid 1990's by Armscorp in Baltimore and Red Cloud in Virginia. Others have surfaced on carbines returned to the U.S. Army by other nations. Thousands of these barrels have been sold retail. Over the years several companies and/or owners have attempted to correct the ones out of spec. Others have added markings to some to make them appear to have been accepted by the U.S. government.

Given the totality of the history of these barrels it would be wise to avoid purchasing one unless you have a gunsmith capable of verifying the barrel meets specifications. At least one owner has had the gas piston housing of his Herlo barrel rupture during firing. Others report they've had no problems with theirs.

Proof Marks

Ordnance Inspector Training Manual SA-ITM-S201 dated 04 Sep 1951 states: "Each assembled Carbine, spare Barrel, and spare Bolt Assembly shall be subjected to firing of one Government Standard Cartridge, High Pressure Test, Carbine, Cal .30, MI8, or other approved test (See applicable C.I.P.) under the supervision of the inspector." Eventually followed by: "Immediately after proof-firing and inspection of the proof-fired components, each Barrel shall be marked with the letter "P" on the top of the Barrel at a point approximately two inches in front of the Front Band."

While this was the standard for proof marks in 1951, examination of the proof marks on the actual barrels have shown policies/procedures may have differed from one barrel manufacturer/prime contractor to another. Also with the same manufacturer at different times.

Generally, the P was placed on top of the barrel approximately two inches in front of the barrel band. If an early barrel band was eventually replaced with the barrel band having the bayonet lug the P may be obscured by the bayonet lug.

Proof mark on top of the barrel forward of the barrel band. The size of the P can vary.

Barrels manufactured by Winchester may have the letter P
and/or a small oval containing an overlapping P and W,
Winchester's hallmark proof mark.

Sometimes the proof mark may be found on top of barrel above the chamber. Not to be confused
with marks other than a P sometimes found in this location. Other marks in this location were
used internally by companies with meanings known only to that company.

Less common, the proofmark may be located elsewhere

Each prime contractor who manufactured their own barrels manufactured extra barrels for use as spares. Also for the Government Free Issue Barrel Program along with Buffalo Arms, Marlin and Brown-Lipe-Chapin as Inland. Barrels produced as extras were to be proof tested and marked by the manufacturer. To save the time and eliminate duplicated effort the Government Free Issue Barrel Program indicated the barrels for their program were not to be proof tested and marked until they were assembled to the receiver. However, some manufacturers continued to proof fire and mark their barrels. This resulted in some barrels being proof tested and proof marked twice, once by the barrel manufacturer and again when assembled to the carbine.

Examples of double P's on spare barrels proof tested by both the barrel
manufacturer and the prime contractor who assembled the carbine.

National Postal Meter initially used the letter P but switched to the use of a punch mark instead, placed where the letter would have gone. If the carbine was assembled when test fired, all prime contractors added a punch mark to the bolt and another to the receiver in addition to proof mark they used on the barrel. Punch marks on the bolt and receiver and covered on the web pages devoted to these parts.

National Postal Meter initially used the letter P but switched to the use of a punch mark instead.

Examples of spare barrels proof marked with the P by the barrel manufacturer and again with the
punch mark when the barrels were proof tested by National Postal Meter.

Flaming Ordnance Bomb

Flaming Ordnance Bombs may be found on some barrels. They may be located:

The Flaming Ordnance Bomb was commonly used by Ordnance inspectors to indicate a particular part had been examined and passed inspection. Their presence on a barrel is assumed to have the same meaning but no proof of this has been found.

Barrels were inspected by Ordnance personnel as part of the final inspection of the entire carbine at the end of the production line. It was Ordnance policy for proof of this inspection to be stamped into the right side of the buttstock. Ordnance inspection of completed barrels appears to have varied by the Ordnance District and/or Ordnance inspectors assigned to a particular manufacturer as the use of the Flaming Ordnance Bomb was specific to certain manufacturers.

The Flaming Ordnance Bomb as a Manufacturer's Trademark

Flaming bombs were used by a few manufacturers as a form of trademark. Their use was limited with the exception of parts manufactured by Underwood-Elliott-Fisher who used the mark on various parts throughout production. These included the barrels they manufactured where the mark appears below their name and the date the barrel was manufactured.

Crossed Cannons

The crossed cannons mark, often referred to as a cartouche, was Ordnance's trademark. Historically it was used by Ordnance inspectors as a proof of inspection mark on many different items. In the case of the prime contractors manufacturing .30 caliber carbines the design of the small details of the cartouche were specific to Ordnance inspectors assigned to a specific prime contractor.

Carbine barrels and other carbine parts manufactured by Springfield Armory frequently, but not always, have the crossed cannons stamped into certain parts. Carbine barrels manufactured by Buffalo Arms may also have the crossed cannons. It is assumed these were Ordnance inspection marks but evidence of this has yet to be located. If present on a carbine barrel they are normally located on the flat bottom between the breech and gas cylinder.


Manufacturers sometimes used symbols on the bottom of the barrel between the receiver and gas cylinder for
internal purposes known only to them. These marks on barrels manufactured and used by Inland are often
referred to as "Inland Hieroglyphics" due to quantity commonly found on their barrels. The quantity used
by Inland was more than any other manufacturer and can often be used to identify the barrel as having
been made and used by Inland.

Occasionally hidden amongst these markings are a set of crossed cannons or the Brown-Lipe-Chapin subcontractor
code. Barrels manufactured by Brown-Lipe-Chapin and used by Inland typically do not have the quantity present
on those manufactured and used by Inland.

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