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The table below contains the maximum Cartridge Overall Length (COAL) for popular detachable magazines for rifles. This is important to consider when picking a rifle cartridge to ensure you have enough clearance to “chase the lands”, which just means as your chamber throat begins to naturally erode from use you seat your bullet further and further out so that it maintains the same relative position with the rifle lands. Many people start with their COAL almost maxed out in their magazine, and as their chamber throat starts to wear they are forced to choose between loss of accuracy from not being able to seat the bullet close to the rifle lands, or seating the bullet too far out to fit in the magazine.
Considering the COAL of the magazine you plan to use can help you decide what cartridge is the best long-term fit. Unfortunately this information is harder to find than it should be. In fact, I had to contact Accuracy International to get some of these numbers. Hopefully having it listed here helps you make an informed decision.
- Accuracy International (View Products at MidwayUSA) – These are the detachable box magazines (DBM) made for the Accuracy International Chasis System (AICS). These are the most popular detachable magazines in precision shooting.
- Wyatt’s Outdoors (View Products on MidwayUSA) – This is a less known manufacturer of high quality detachable box magazines and bottom metal, but I personally use them and haven’t had any issues with them at all. One benefit of the Wyatt’s magazines is a little more COAL over AI magazines. This is because they don’t have the little plastic insert at the front of the magainze like the AI magazines. The difference varies based on the type/size of the magazine, but for the long action that I shoot … I thought the tenth of an inch of additional clearance it gave me was worth giving them a shot, and I’m glad I did. They aren’t any cheaper than the AI mags, but the build quality is equal to the AI mags.
| Magazine Size | Recommended COAL for Accuracy International DBM | Recommended COAL for Wyatt’s Outdoors DBM |
|---|---|---|
| Short Action (223) | 2.550″ | 2.850″ |
| Short Action (308) | 2.880″ | 2.880″ |
| Long Action (30-06, 300 Win Mag) | 3.625″ | 3.700″ |
| XL Action (338 Lapua) | *3.646″ | 3.790″ |
*Accuracy International also mentioned they have a CIP magazine that has an interior OAL of 3.764″. The measurement above is for what they referred to as their “small 338” magazine … for whatever that is worth.
