Originally Posted by Max Heat
I just wanted to add that after doing a site search, I found information stating that the 7 has about double the freebore that the 300 has. That ALREADY sounds like a bad starting point, for throat life on the 7. But I did come up with some conflicting numbers for the 7. One of them is .220, and the other is .400 (wow). Which one is correct?
For the 7rums I had it was over .4" freebore. The one I gave back with a loose chamber was just over 4" to the lands, and the one that shot well was an even 4.1" to the lands with a sierra bullet; so .4" and .5" freebore.
My 300 rum is around .2" depending on real oal and bullet used. If I hold saami round length at 3.6" it's about .2". The 300 rum already has enough rounds on it to kill a 7mm rum barrel, and it still has strong rifling with little wear. I'm guessing she'll go another 1000 rounds or more before I retire and rebuild it.
The freebore is actually rather necessary especially in the 7rum, since it is so overbore. You do pay some price in round count, but they work very well as designed.