I just bought a neat little chamber adapter that lets me shoot 7.62X39 in a .308 by basically filling the chamber with a .308 cartridge-sized hollow adapter that holds a Russian cartridge inside it. (I use such an adapter to shoot .45 LC in my Martini-Henry "Zulu" rifle, a cheap solution to very expensive and rare ammo.)
The Russian bullet in the .308 adapter travels a short distance unrestricted through a smooth and loose section of the adapter before entering the throat's rifling. .
Joop brought up an interesting and very relevant thought on such an adapter -that it might possibly lead to damage to the throat of the rifle using the adapter.
I've been wondering if this might happen. It seems it is possible for two reasons, but I'm not sure whether it would really be a problem:
1) Hot gases might leak past the bullet base as it is fired and going through the loose straight section, burning the throat more than they would do if behind the bullet. Are hot gases more destructive to the throat in this situation than if they hit a microsecond later behind the bullet normally? Doesn't seem like it, but maybe.
2) The bullet might enter the throat angled or off center a bit from free travel before hitting the throat, resulting in uneven pressure and wear. In this scenario the FMJ bullet from the Russian round is slightly skewed and sort or rattles into the throat, seemingly very possible.
The second scenario seems more likely to damage things than the first to me, but it is perhaps no more dangerous to the barrel than using shorter bullets in the regular .308 chambering that don't reach all the way to the throat, like soft-points. It used to be that for maximum accuracy it was believed a bullet had to be pushed right up against the throat, but I think that belief may have been discarded, meaning lots of bullets come rattling up to the throat a bit loose.
As I very much value Joop's wondering about the possibility of barrel erosaion or wear and don't know an answer, any thoughts from other members? I haven't tried the adapter yet.
.
The Russian bullet in the .308 adapter travels a short distance unrestricted through a smooth and loose section of the adapter before entering the throat's rifling. .
Joop brought up an interesting and very relevant thought on such an adapter -that it might possibly lead to damage to the throat of the rifle using the adapter.
I've been wondering if this might happen. It seems it is possible for two reasons, but I'm not sure whether it would really be a problem:
1) Hot gases might leak past the bullet base as it is fired and going through the loose straight section, burning the throat more than they would do if behind the bullet. Are hot gases more destructive to the throat in this situation than if they hit a microsecond later behind the bullet normally? Doesn't seem like it, but maybe.
2) The bullet might enter the throat angled or off center a bit from free travel before hitting the throat, resulting in uneven pressure and wear. In this scenario the FMJ bullet from the Russian round is slightly skewed and sort or rattles into the throat, seemingly very possible.
The second scenario seems more likely to damage things than the first to me, but it is perhaps no more dangerous to the barrel than using shorter bullets in the regular .308 chambering that don't reach all the way to the throat, like soft-points. It used to be that for maximum accuracy it was believed a bullet had to be pushed right up against the throat, but I think that belief may have been discarded, meaning lots of bullets come rattling up to the throat a bit loose.
As I very much value Joop's wondering about the possibility of barrel erosaion or wear and don't know an answer, any thoughts from other members? I haven't tried the adapter yet.
.