A kind member sent me some pics of an Ishapore made SMLE No2A which is virtually an exact copy of the No1 except for two things. First, it is chambered for the 7.62 NATO cartridge, and second it uses modern metallurgy to handle the pressure. As we all know the No1 is not strong enough to handle 7.62 pressure safely.
I was not so much interested in the 7.62 as conversion to other calibres and what alterations to the bolt head in particular might be needed. The 303 Rim is almost as big as the bolt head. The SMLE extracts and ejects by forcing the rim against the left receiver wall and holding it there until it strikes the ejector stud. I figured that it wouldn’t work too well with smaller case heads. The Ishapore No2A does it with nothing more than a longer extractor hook which surprised me as I was expecting more radical modifications. That means a No1 or No4 can be rebarrelled for any of the many calibres that share the 12mm case head diameter, or the belted magnums, as long as pressures are kept within SMLE limits.
Conversion to smaller heads like the 223 are more complicated but still not difficult. The favoured method is to silver solder a ring to the bolt face to create a recess. It is a popular conversion in thre UK and Australia. As a matter of interest back thrust not chamber pressure is the limiting factor. The 7.62 NATO is not practical because both chamber pressure and back thrust are greater than the 303 British. But the 223, although having a higher chamber pressure, is safe because the back thrust on the bolt is much less than the 303.
This means that the SMLE action can easily be converted to other calibres. Also that it is easier in some than the 98 Mauser. At the very least, don’t be too quick to write the SMLE off, and if you have one, or an action or two, they might be more useful than you had thought.
[Originally posted to SATalkGuns -- Admin]