Headspace for 9mm Luger or 9mm Parabellum Reloading

 

9mm Luger Round
in Glock 26 chamber

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People talk about headspace when they reload ammunition for firearms. Headspace is a distance measured from chamber cartridge stop (the portion of the chamber that stops the forward movement of the cartridge) to the closed breech face (bolt face). The following pictures depict the chamber and headspace for 9mm Luger cartridges in a Glock 26. See also Ammunition Reloading Instruction & Reviews.

9mm Glock 26 Pistol Chamber & Cartridge Stop 9mm Luger Round Chambered in a Glock 26

 

For straight wall rimless cases such as the 9mm Luger, headspace is controlled by the case mouth butting up against a corresponding ledge (chamber cartridge stop) within the chamber of the firearm.

Headspace is important for the proper and safe operation of a firearm. Headspace problems occur when the headspace is either too long or too short. This may be the result of the firearm itself or the improperly sized ammunition used in the firearm. If the headspace is too short the bottom of the cartridge will protrude out of the chamber and preventing the action from closing or causing firing pin firing problems. If the headspace is too long, the case may experience excessive stretching and deformation upon firing.

When a round is fired, pressure within the case of the cartridge builds up and expands the case walls outwards in all directions. The sides of the case are pushed against the chamber walls gripping them tightly. The rear of the case may move rearward a few thousandths of an inch, resulting in thinning and weakening of the case walls where the case stretched, usually just ahead of the extractor groove, or rim. As the pressure subsides the brass will retract and release its grip on the chamber wall permitting extraction from the chamber. Headspace problems in general are most commonly associated with bottle-necked cartridges.

 

Headspace Definition

In firearms, headspace is a distance measured from chamber cartridge stop (the portion of the chamber that stops the forward movement of the cartridge) to the closed breech face.

 

Related Dimensions

Glock 26
Headspace length = .750"
Chamber ID = .390" (corrected dimension)

 

Glock 19
Chamber ID of a 9mm Glock 26 Pistol = .390"
9MM Luger Case OD (3 range pickups, expanded) = .3860", .3860", .3885"
9MM FMJ Bullet OD = .3565"

 

Headspace Feedback Comments

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9MM Glock Chamber Diameter

February 08, 2012
ISN'T THE CHAMBER DIAMETER SOMEWHAT SMALL IN YOUR DIMENSIONS? ALSO YOU MISSPELLED CHAMBER (CAMBER). I NEVER HEARD OF "CAMBER" IN A GUN.
SINCERELY,
RAY - FORMER WINCHESTER PRODUCT ENGINEER


Response - Ray,
Thanks for the corrections. I don't know where that .035" chamber ID came from. I will update it accordingly.
Best regards,
Tanner

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Glock 26 Chamber ID

January 22, 2011
Chamber cartridge of a 9mm Glock 26 Pistol
Headspace length = .750"
Chamber ID = .035"
surely the chamber ID (inside diameter) is not .035"
M


Response - M
Thanks for pointing that out. I don't know where the .035" came from. The chamber ID of my Glock 26 measures out to be .390" at the mouth or opening. The chamber tapers down to about .3805" as far in as my calipers go.
Thanks again.
Tanner

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