I recently picked up barrels for a 6mm creedmoor project and a 6.5 PRC project. The creedmoor is a #3 sporter bartlein 5r 7.5 twist and the PRC is a #4 sporter profile Krieger 4 groove 7.5 twist. I have not had either of these chambered yet but was researching load data and started reading about issues with groove counts influencing the bullets blowing up. Previously, I had never heard of such a thing, but it seems like there is growing validity to the theory despite most of the evidence being anecdotal.
I am planning to cut the PRC to 20” and was hoping to shoot 147 ELD-Ms but in this deep dive, it seems like these bullets are the most prone to blowing up. While the 3 and 4 groove barrels (anecdotally) seem to have the most correlation to the issue, it would appear that folks have issues regardless of grooves and if I am reading between the lines, speed seems to be a major contributor. At 20” and despite the 7.5 twist, I am assuming my speeds will still be in the safe zone from an excessive RPM perspective.
Most of the info on this 4 groove issue is several years old at this point and I’m not sure if it really holds water still or seemed to be relegated to the handful of individuals who were posting on the topic. Krieger barrels still seem to have high praise (most of which are 4 groove from what I can tell) and there’s a lot of love for the 147s on here, which I assume lots of people are shooting them at higher velocities without stories/issues of jacket separation.
Anyone on here have any further/more recent insight? I have been debating saving the barrel for a different chamber, or just chambering it as intended and shooting Bergers (156) which seem to have far fewer reported issues and would work better with the faster 7.5 twist anyway.
Curious to hear thoughts, I’m probably over analyzing but it’s an interesting subject. Thanks in advance
I am planning to cut the PRC to 20” and was hoping to shoot 147 ELD-Ms but in this deep dive, it seems like these bullets are the most prone to blowing up. While the 3 and 4 groove barrels (anecdotally) seem to have the most correlation to the issue, it would appear that folks have issues regardless of grooves and if I am reading between the lines, speed seems to be a major contributor. At 20” and despite the 7.5 twist, I am assuming my speeds will still be in the safe zone from an excessive RPM perspective.
Most of the info on this 4 groove issue is several years old at this point and I’m not sure if it really holds water still or seemed to be relegated to the handful of individuals who were posting on the topic. Krieger barrels still seem to have high praise (most of which are 4 groove from what I can tell) and there’s a lot of love for the 147s on here, which I assume lots of people are shooting them at higher velocities without stories/issues of jacket separation.
Anyone on here have any further/more recent insight? I have been debating saving the barrel for a different chamber, or just chambering it as intended and shooting Bergers (156) which seem to have far fewer reported issues and would work better with the faster 7.5 twist anyway.
Curious to hear thoughts, I’m probably over analyzing but it’s an interesting subject. Thanks in advance
