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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
+P Throating
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<blockquote data-quote="Tumbleweed" data-source="post: 2789297" data-attributes="member: 9281"><p>Ok, so I've decided to chime in here with my experience with one +P throat. This is just sharing my experience and in no way trying to discourage anyone from going ahead with a +P. </p><p>Bob and Shawn Carlock re-barreled, chambered and +P throated and cerakoted my full custom Rem 700 300 RUM. The work was second to none and both Bob and Shawn were very personable and showed me around the shop when I picked up the rifle. I will very likely have them do more work for me in the future.</p><p></p><p>Barrel:</p><p>34" finished length Bartlein 5r 1:9 to 1:8 transitional twist 400MOD throated for 245 EOL Bergers.</p><p></p><p>Barrel break in didn't go so well, lots of copper that didn't seem to go away. After talking with both Bartlein and Shawn, I decided to stop cleaning and just go with it. Accuracy right off the bat was exceptional printing 5 side by side groups at 250 yards in the .1's to .2's MOA in load development. ES was typically around 20fps prior to barrel speed up. This was using RL33, ADG Brass and Fed 215M. </p><p></p><p>The barrel is typically cleaned down to bare metal and HBN coated every 50-70 rounds. I always keep a close eye out for a carbon ring and have not had an issue with that. I have never allowed more than 3 shots at a time (rare) and the barrel has never been hot. It is running some pressure. </p><p></p><p>Speed up finally happened at about 180 rounds where I backed my charge off by 1 grain to get back down to 3150fps with the 245. I attributed the poor break in and longer than normal speed up to the harder 400MOD barrel material. Accuracy was still very good and copper fouling was not causing any issues at this point. ES in this time frame was under 12 fps.</p><p></p><p>I did some testing with the 250 Atips (245 Bergers could not be found) and in my testing discovered that RL50 produced the absolute best velocity with the A-tips. I attempted to develop a load with the 250 and RL50. Initial results were great with 6 shots in pressure testing going into nearly the same hole at 100 yards. Seating depth testing at a low charge was producing pairs in the .2's. As I moved to charge testing, I found that my ES was high, always. 30-40fps. I did find a sweet spot that would produce accuracy in the .2's to .3's IF velocities happened to remain stable (3150fps) for that group. It would not consistently repeat due to ES/harmonics. I tested neck tension and changed primers to no avail. I even jammed bullets .010" just to see if it would help with ES. It got worse, up to 60fps ES. Round count on the barrel was now at 350. I initially attributed the high ES to the very slow powder...maybe not being completely burned. </p><p></p><p>I determined that I would just go back to my 245 Berger load. Having put 120 rounds down the tube in testing, I decided to take a measurement to the lands. This is where I started to see a problem. Throat growth appeared to be .050" over the last 150 rounds. A quick look with the bore camera confirmed my fears in that I could see almost no sign of the +P section of throat anymore. There may be .0001" of land depth left, but's it almost imaginary it's so faint. </p><p></p><p>I took it out with my RL33 245 Berger load and tested seating depth, it was still within .003" of optimal shooting producing .3 MOA. However, I lost 50fps. It took 1.1 grains to bring it back up to the normal speed/load but now I have ES in the 40fps range with RL33! Accuracy for now is still very good. This is an ELR gun for one mile plus shooting. Without ES inside of 10-12fps, I'm ****ing in the wind. Very frustrated trying to decide what to do now. I essentially have a "freebore" of 1 1/8" in this thing. I don't see how I could ever fix my ES problem with that going on.</p><p></p><p>My next step will be to take it to 2K and see what it does vertically. I may be surprised. The only fix I see is to have a smith chop off 1" plus of the shank and re-chamber with a traditional throat. So, my experience seems to align with Kirby's. Very disappointing. The hope was that the harder 400MOD barrel would actually prolong throat and barrel life.</p></blockquote><p></p>
[QUOTE="Tumbleweed, post: 2789297, member: 9281"] Ok, so I've decided to chime in here with my experience with one +P throat. This is just sharing my experience and in no way trying to discourage anyone from going ahead with a +P. Bob and Shawn Carlock re-barreled, chambered and +P throated and cerakoted my full custom Rem 700 300 RUM. The work was second to none and both Bob and Shawn were very personable and showed me around the shop when I picked up the rifle. I will very likely have them do more work for me in the future. Barrel: 34" finished length Bartlein 5r 1:9 to 1:8 transitional twist 400MOD throated for 245 EOL Bergers. Barrel break in didn't go so well, lots of copper that didn't seem to go away. After talking with both Bartlein and Shawn, I decided to stop cleaning and just go with it. Accuracy right off the bat was exceptional printing 5 side by side groups at 250 yards in the .1's to .2's MOA in load development. ES was typically around 20fps prior to barrel speed up. This was using RL33, ADG Brass and Fed 215M. The barrel is typically cleaned down to bare metal and HBN coated every 50-70 rounds. I always keep a close eye out for a carbon ring and have not had an issue with that. I have never allowed more than 3 shots at a time (rare) and the barrel has never been hot. It is running some pressure. Speed up finally happened at about 180 rounds where I backed my charge off by 1 grain to get back down to 3150fps with the 245. I attributed the poor break in and longer than normal speed up to the harder 400MOD barrel material. Accuracy was still very good and copper fouling was not causing any issues at this point. ES in this time frame was under 12 fps. I did some testing with the 250 Atips (245 Bergers could not be found) and in my testing discovered that RL50 produced the absolute best velocity with the A-tips. I attempted to develop a load with the 250 and RL50. Initial results were great with 6 shots in pressure testing going into nearly the same hole at 100 yards. Seating depth testing at a low charge was producing pairs in the .2's. As I moved to charge testing, I found that my ES was high, always. 30-40fps. I did find a sweet spot that would produce accuracy in the .2's to .3's IF velocities happened to remain stable (3150fps) for that group. It would not consistently repeat due to ES/harmonics. I tested neck tension and changed primers to no avail. I even jammed bullets .010" just to see if it would help with ES. It got worse, up to 60fps ES. Round count on the barrel was now at 350. I initially attributed the high ES to the very slow powder...maybe not being completely burned. I determined that I would just go back to my 245 Berger load. Having put 120 rounds down the tube in testing, I decided to take a measurement to the lands. This is where I started to see a problem. Throat growth appeared to be .050" over the last 150 rounds. A quick look with the bore camera confirmed my fears in that I could see almost no sign of the +P section of throat anymore. There may be .0001" of land depth left, but's it almost imaginary it's so faint. I took it out with my RL33 245 Berger load and tested seating depth, it was still within .003" of optimal shooting producing .3 MOA. However, I lost 50fps. It took 1.1 grains to bring it back up to the normal speed/load but now I have ES in the 40fps range with RL33! Accuracy for now is still very good. This is an ELR gun for one mile plus shooting. Without ES inside of 10-12fps, I'm ****ing in the wind. Very frustrated trying to decide what to do now. I essentially have a "freebore" of 1 1/8" in this thing. I don't see how I could ever fix my ES problem with that going on. My next step will be to take it to 2K and see what it does vertically. I may be surprised. The only fix I see is to have a smith chop off 1" plus of the shank and re-chamber with a traditional throat. So, my experience seems to align with Kirby's. Very disappointing. The hope was that the harder 400MOD barrel would actually prolong throat and barrel life. [/QUOTE]
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