Quickdraw,
The differences between 7.62 and 308 are small. Regarding chamber length, 308 no-go gauge length is 1.634" while 7.62 no-go gauge length is 1.6405" so as you have said, 7.62 is a little longer than 308.
You will see some internet pundits saying that 308 is rated at 62,000 psi while 7.62 is rated at 50,000 psi - so 308 should not be shot in 7.62 rifles. I believe that this is incorrect. The 50,000 statistic for 7.62 is a measure of CUP (copper unit pressure) which is not directly translatable into psi. One estimation formula puts 50,000 CUP at about 76,000 psi. In any event, for all practical purposes the two rounds are interchangeable.
The only consequence of the extra headspace of the NATO chamber is in regard to your reloading setup and to brass life. If you full-length size your brass to 308 SAAMI specs, it will stretch more in the NATO chamber and you will get fewer reloads from your brass. There may or may not be an accuracy effect but I have not found this to be measurable. I have neck-sized and minimally shoulder bumped fire-formed M305 brass (and it was longer than 308 spec after this process) and have not seen a meaningful improvement in groups versus brass full-length sized to 308 SAAMI spec.
Hope this answers your question.
The differences between 7.62 and 308 are small. Regarding chamber length, 308 no-go gauge length is 1.634" while 7.62 no-go gauge length is 1.6405" so as you have said, 7.62 is a little longer than 308.
You will see some internet pundits saying that 308 is rated at 62,000 psi while 7.62 is rated at 50,000 psi - so 308 should not be shot in 7.62 rifles. I believe that this is incorrect. The 50,000 statistic for 7.62 is a measure of CUP (copper unit pressure) which is not directly translatable into psi. One estimation formula puts 50,000 CUP at about 76,000 psi. In any event, for all practical purposes the two rounds are interchangeable.
The only consequence of the extra headspace of the NATO chamber is in regard to your reloading setup and to brass life. If you full-length size your brass to 308 SAAMI specs, it will stretch more in the NATO chamber and you will get fewer reloads from your brass. There may or may not be an accuracy effect but I have not found this to be measurable. I have neck-sized and minimally shoulder bumped fire-formed M305 brass (and it was longer than 308 spec after this process) and have not seen a meaningful improvement in groups versus brass full-length sized to 308 SAAMI spec.
Hope this answers your question.
