How the Swiss Headspaced their rifles, A post by Dale Ding.
Headspacing Swiss rifles... how was it done?
As a reminder, the purpose of "correct headspace" is to allow any in-spec firearm to chamber any in-spec cartridge, through good design practices accommodating for tolerance stacking, and thorough QC. In Swiss W+F terms, this dimension is called the "Patronenlagertiefe", or chamber depth.
On both the IG11-Kar. 11 and Kar. 31, after the barrel is clocked in place via alignment of the reference marks, the headspace is adjusted by a combination of the correct bolt head length (available in 0, +0.05mm, +0.10mm and +0.15mm), and lengthening the chamber via a special hand reamer (as shown below).
The actual physical dimension is constantly checked with a headspace gauge named "C-Lehre", which has a critical dimension "A" corresponding to the base of the cartridge to the conical portion. These gauges were available from 44.45mm to 44.850mm, in 0.025mm increments.
To actually confirm correct headspace after assembly, the prescriptions were as follows:
For the IG11-Kar. 11: With a relaxed striker spring, the 44.45mm gauge should close without binding. The 44.5mm gauge can offer slight resistance, and the 44.6mm gauge must offer resistance.
For the Kar. 31: the 44.45mm gauge should close without binding. The 44.6mm gauge can offer slight resistance, and the 44.625mm gauge must offer resistance.
Overall, fascinating stuff!
Source: RUAG archives, E5210-01#1999/23#88*
Headspacing Swiss rifles... how was it done?
As a reminder, the purpose of "correct headspace" is to allow any in-spec firearm to chamber any in-spec cartridge, through good design practices accommodating for tolerance stacking, and thorough QC. In Swiss W+F terms, this dimension is called the "Patronenlagertiefe", or chamber depth.
On both the IG11-Kar. 11 and Kar. 31, after the barrel is clocked in place via alignment of the reference marks, the headspace is adjusted by a combination of the correct bolt head length (available in 0, +0.05mm, +0.10mm and +0.15mm), and lengthening the chamber via a special hand reamer (as shown below).
The actual physical dimension is constantly checked with a headspace gauge named "C-Lehre", which has a critical dimension "A" corresponding to the base of the cartridge to the conical portion. These gauges were available from 44.45mm to 44.850mm, in 0.025mm increments.
To actually confirm correct headspace after assembly, the prescriptions were as follows:
For the IG11-Kar. 11: With a relaxed striker spring, the 44.45mm gauge should close without binding. The 44.5mm gauge can offer slight resistance, and the 44.6mm gauge must offer resistance.
For the Kar. 31: the 44.45mm gauge should close without binding. The 44.6mm gauge can offer slight resistance, and the 44.625mm gauge must offer resistance.
Overall, fascinating stuff!
Source: RUAG archives, E5210-01#1999/23#88*
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