A – D

annealed_receiverAlso Lead Pot Annealed. A process used to soften the rear of the receiver to prevent cracking when struck by the bolt during recoil. After the development of the grenade launcher, a new steel alloy less prone to cracking was used to make receivers. Older receivers were dipped in molten lead to reduce brittleness. This process darkened the appearance of the dipped section, resulting in “two-tone” receivers.
arrowheadA style of receiver logo used on the earliest International Harvester rifles, in which the arrangement of the text lines resembles an arrowhead. Collectors believe these were supplied by Springfield Armory and are among the very first rifles produced by IHC.
baseProperly “bracket”; the dovetail base fastened to the receiver of the M1C Sniper rifle. The telescope and mount slide onto the bracket. See M1C.
birchThe wood used to make replacement stocks and handguards in the late 1950′s. Original specifications called for walnut, but difficulty in obtaining it resulted in a switch to birch in some rebuild programs and for replacement guards.
bright_chamberIn original assembly at Springfield Armory, the chamber area of the barrel was not Parkerized and appears bright. During rebuild, a newly refurbished barrel/receiver assembly was refinished and the chamber area Parkerized in the process. A bright chamber is a clue to originality.
british_proofsA set of stampings required by British law on any firearm exported from England. The 1941 – 1942 Lend Lease rifles imported in the 1960’s carried these marks in the barrel date area, and later imports on the top of the barrel between the rings of the gas cylinder. Collectors generally dislike non-standard markings.
cartoucheThe collector term for the mark stamped into the left side of the stock upon original acceptance of the rifle by the government. The earliest stamps bore the initials of the manufacturer over the initials of the inspector under whose authority it was accepted. In late 1940 the Springfield Armory format was changed to use the initials of the armory Commandant. At Winchester the new type used GHD, the initials of the Chief of Ordnance. In 1953 the old cartouche was changed to the boxed Eagle and Stars called the Defense Acceptance Stamp. Springfield, Harrington & Richardson, and International Harvester all used the DAS from that time onward.
cmpCivilian Marksmanship Program headquartered in Anniston, Alabama, formed in 1996 to succeed the DCM. All M1 rifles in Army inventory were transferred to them for sale to qualified buyers. CMP supports the National Matches at Camp Perry. See thecmp.org/.
comp_springProperly “compensating spring.” A small spring butted to the front of the keystone operating rod spring to improve functioning in early rifles. This required a follower rod with a thin body over which the comp spring fit. The comp spring was eliminated in 1940 (see KEYSTONE SPRING).
curved_sideThe profile of the operating rod boss. Early rod bosses were cut in an arc; later rods were cut straight.
Rifles loaned to Denmark during the Cold War and returned by them in 1998. CMP sold these rifles to the public.
dashA component of some parts marking (see DRAWING NUMBER). Some parts marking included a dash between the letter of the mark and the main number, as well as a dash between the number and the Revision Number. Parts marks with dashes are usually earlier than the same number without a dash.
dash_nbrThe revision number, often separated from the main part number by a dash. The part blueprint was revised when some element of construction was changed, even if the change did not entail a change of shape. Parts constructed according to the new drawing were marked with the number of the revision to the original drawing. The digit 4 in B-8881-4 above represents the fourth revision to the original long butt plate screw
Department of Civilian Marksmanship, a government agency created in 1916 to encourage shooting by civilians as a cadre in time of war. DCM sold surplus military weapons and ammunition to qualified civilians as part of the mission. Political controversy surrounded this program, and it was privatized as the Civilian Marksmanship Program in 1996, ending government involvement in weapons sales. All M1 rifles in Army inventory were transferred to the newly formed CMP.
A government process used to “demilitarize” or destroy rifles by cutting the receiver and barrel in half. Hundreds of thousands of rifles were demilled and the receiver halves sold as scrap (see REWELD). Modern demilling uses a shredder nicknamed “Captain Crunch”.
drawing_numberA number stamped into many parts, indicating the blueprint covering the construction of that part. This number was also the Part Number, and was composed of a letter indicating the size of the blueprint, a unique number assigned to that part, and a number indicating the revision to the original drawing. In early rifles most parts were numbered, but most parts marking was dropped under the pressure for increased production.

E – L

A hole bored into early triggers; dropped in 1941.
field_stripTo disassemble a rifle into the three main groups: barrel and receiver, stock, and trigger group.
flush_nutThe small nut that held the rear sight elevation knob in place on early rifles. Because the sight tended to loosen, the flush nut was replaced by a rectangular bar that could apply greater tension (see LOCK BAR).
gap_letterA style of receiver logo on International Harvester rifles, in which there is a space between U.S. and RIFLE and between CAL. and .30M1. These receivers were supplied by Springfield Armory to help IHC meet production quotas.
gas_portThe hole in the barrel that admits propellant gas into the gas cylinder. The GCA standardized the term “Gas Port Rifle” to identify the spline-type gas system used from 1940 to replace the original Gas Trap system.
gas_trapThe collector term standardized by the GCA in 1995 for the first type of gas system that utilized a false muzzle to deflect or “trap” the gas into the gas cylinder. The early barrel was threaded at the muzzle and the gas cylinder screwed onto it. The gas plug slipped into the front of the cylinder and was held in place by a screw. This system caused accuracy problems because the plug through which the bullet passed deformed under the heat generated by rapid fire. It was replaced in late 1940 by the “Gas Port” system in which the gas entered the cylinder through a hole bored in the barrel. The gas cylinder slipped onto three splines cut into the barrel and the gas plug was eliminated. Approximately the first 50,000 rifles used the Gas Trap system, but almost all of them were eventually upgraded to the Gas Port design. Unmodified rifles and parts command a huge premium from collectors.
greekAny of the M1’s loaned to Greece during the Cold War and returned to the CMP in 2002 for sale to the public.
head_spaceThe length of the bullet chamber as measured from the face of the closed bolt to a datum point in the barrel where it contacts the cartridge. The GI acceptable .30-06 measurement can vary from 1.940 inches to 1.949 before rejection. A rifle with excessive headspace is dangerous to fire.
heat_lotA code stamped into the receiver, bolt, and barrel to identify the batch of steel used. Raw material delivered by the steel supplier included a list of the alloys in the batch. Springfield metallurgists assigned a code to that batch or “heat” (also “melt”) of steel. The code identified the supplier and the lot, such as REP 23A. The heat lot was a quality control measure that would allow all parts made from a particular batch to be identified if problems like cracking developed.
keystone_springThe operating rod spring used on early models, made from keystone- shaped wire that appears square. The operation of this spring was sometimes sluggish, and a second “compensating” spring was added. In 1940 the Wallace Barnes Company developed a roundwire spring that replaced both and was used from 1941 to the end of production.
lateAny part with final characteristics that is familiar to all.
lend_leaseDuring the early days of WW II the US sent large quantities of weapons to Great Britain, including 38,001 M1 rifles. Most of these rifles were not used and were imported back to the US by Interarmco for sale on the civilian market. They bear a series of British proof marks, usually in the barrel date area. When imported, these rifles also carried a band of red paint around the front handguard denoting that they are not the standard British caliber, but this mark was usually removed by collectors. See BRITISH PROOFS.