Delta L problem or "One size doesn't fit all"

[Edward Horton]

Many times I have said something was wrong with our American .303 British cases now even the European CIP seems to agree.
("practical incompatibility with ammunition made for the corresponding chambering")

Delta L problem
The delta L problem (ΔL problem) is a condition that occurs regarding certain firearms chambers and their practical incompatibility with ammunition made for the corresponding chambering. The ΔL refers to a Commission Internationale Permanente (C.I.P.) geometric dimensioning and tolerancing definition for firearms cartridge cases which are longer than the chamber they have to fit in.

Conflicting industry standards
The main cause for the ΔL is that the two main civilian ammunition and firearms industry standards organizations C.I.P. and SAAMI have assigned different standards for the same cartridges. This leads to officially sanctioned conflicting differences between European and American ammunition dimensions and chamber dimensions. Since C.I.P. and SAAMI do not rule nor control civilian ammunition standards worldwide other causes for conflicting standards leading to ΔL issues are also possible.

Firearm cartridges with otherwise problematic headspace
There are also some firearm calibers with problematic headspace listed by C.I.P.[2]
The headspace defined by:
Depth of rim recess
.303 British
.38 Sp AMU
6.35 Browning
7.65 Browning
9 mm Browning long

Delta L problem - Wikipedia, the free encyclopedia

Information

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[ireload2]

The description of the Δ L problem was related to certain action types that would not close on a maximum material cartridge with a minimum material chamber.
The .303 was mentioned not as a ΔL problem but one of problematical headspace.

CIP has a problem when it tries to force cartridge drawings to fit the CIP drawing dimensioning scheme. You will note on the drawing of the .30/06 that no where do they mention the head to cone datum length that form the basis for the US designs. Per the old fashioned CIP drawing the head to cone dimension is affected by the diameter of the each end of the shoulder and the location of each end of the shoulder. The US drawings simple treats the head to cone as a basic function dimension and gauges that dimension.