Just be VERY careful if you select and use a bolthead that isn't one of the usual 0 to 3 variants, proofed, as issued.

We had a series of trials many years ago to extend the life of thousands of No4's that were rejected at Base Workshops for failing to CHS on the No2 bolt head. The No3 bolthead was not permitted at Base Workshop level.

I won't go into the technicalities of it all as it has been written up here previously, but in short, failure to CHS was never caused by a worn breech end of the barrel but by worn locking lugs on the bolts or bodies. If you couldn't CHS on a new bolt body, using the full range of bolt heads, then it indicated that the hardening of the rifle body had broken down

Just be warned........................