Thread: 303 headspace gauge

Originally Posted by Carlsen Highway

A simpler way is to just shoot it, and if you don't get a case head separation, then its fine. I could count the .303's that have matching bolts I have seen on one hand.
Once you've shot all your ammo, then just neck size that brass after that.

Yes, and if I may add, if you don't have a neck sizer, you can just partially size / shoulder bump.

The .303 has quite sloping/forgiving shoulders due to the old way of making them, a bundle of Cordite (cf my avatar picture) inserted in a straight walled case, and only after that given the bottleneck crimping. Shoulder bumping has most of the advantages of neck sizing, but additionally ensures they feed well (both for if out in the woods and a bit of dirt gets in, but also if you have different rifles). Bump it back just far enough so it will chamber nicely in any of your LE's. Being rimmed cartridges, they headspace on the rim and not on the shoulders anyway, a useful feature for a battle rifle as it allows generous chamber tolerances.

If just for the range and for a single rifle, neck size only.