The following are notes attributed to the CMP regarding M1- 30 Carbine reloading:

MOST IMPORTANT: The .30 Caliber Carbine case has a maximum length of 1.290”. The fired and reloaded cases should be trimmed to minimum every reloading. Reloading die makers usually specify a longish "trim to" length on the order of 1.285”. The minimum length for Carbine cases is 1.280” and has been observed to be more satisfactory. This 1.280" is the normal factory length of new ammunition.

This length of 1.280” helps prevent failure to lock with the bolt forward but not rotated and subsequent out of battery firing. Too long of cases wedge the bolt forward, but do not allow easy rotation to full lock up. Too long of cases are the main cause of most problems. Carbine cases stretch at seeming random. Trim every reloading. Some cases will be unmarked by the trimmer cutter, others will be partially trimmed on one side, and others will be fully engaged with the trimmer cutter.

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