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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Need help troubleshooting 300 RUM pressure issue.
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<blockquote data-quote="Michael Eichele" data-source="post: 901073" data-attributes="member: 1007"><p>Mark, </p><p></p><p>I had two different custom 300 RUM barrels do the exact same thing. Both started doing it early in their life and one did it less than 70 rounds. It seemed like every time I pulled the trigger the velocity went up and the bolt got stickier. I kept backing off charges and velocities still went up. I fought and fought with it for a couple hundred rounds and it settled in to a point but never stopped settling down completely. After a certain point, instead of dropping charges every few rounds, I only had to drop them every 50 rounds or so. When it was all said and done, the only powder I could get to work in one was H50BMG under the 178 amax and 180 accubond. In the other I was down to 80 grains of H1000 under the 178 amax or 92 grains of H50BMG under the 208 amax. All were reduced velocities but still showed signs of fairly high pressure. </p><p></p><p>Shortly after it started happening on my second barrel, Mike Rock told me it was from severe throat erosion and severe heat checking. He said those will actually increase friction on the bullet dramatically and that is where my high pressure was coming from. A trip to the smith and look through the borescope confirmed his statements. It was bad. Really bad.</p><p></p><p>It can happen VERY fast in a barrel chambered in 300 RUM. Especially if you run top end loads. In my experience, top end loads in 300 rums even without pressure signs initially, kill barrels and fast.</p><p></p><p>I know thats not what you were hoping to hear and I hope I'm wrong but that's most likely the problem.</p><p></p><p>Factory barrels can sometimes hold up better IMHO. They're often hammer forged and subsequently very durable and so rough they can actually improve before going downhill. With a top end fine custom barrel, they have ONLY one way to go. That is downhill. You can't typically improve a good custom bore. They're their best for only one shot. That's their first. They start going downhill after that. The hotter the caliber and the harder you run them, the faster they decline. It's not at all uncommon for the 7mm RUM and 300 RUM customs to go south short of 100 rounds. I get PMs occasionally about how fast one went south. I used to preach my feelings on this matter a lot and caught a lot of flame for it here. Guys not wanting to catch flame would pm me and say yup! You were right! </p><p></p><p>In this case I truly HOPE I am wrong.</p><p></p><p>M</p><p></p><p>EDIT: I almost forgot, make sure there is no carbon ring present either. I'm just guessing here but it doesn't sound like you have enough rounds down it to be a carbon ring but a carbon ring will generate a lot of extra pressure and if not corrected quickly, can kill your barrel as well.</p></blockquote><p></p>
[QUOTE="Michael Eichele, post: 901073, member: 1007"] Mark, I had two different custom 300 RUM barrels do the exact same thing. Both started doing it early in their life and one did it less than 70 rounds. It seemed like every time I pulled the trigger the velocity went up and the bolt got stickier. I kept backing off charges and velocities still went up. I fought and fought with it for a couple hundred rounds and it settled in to a point but never stopped settling down completely. After a certain point, instead of dropping charges every few rounds, I only had to drop them every 50 rounds or so. When it was all said and done, the only powder I could get to work in one was H50BMG under the 178 amax and 180 accubond. In the other I was down to 80 grains of H1000 under the 178 amax or 92 grains of H50BMG under the 208 amax. All were reduced velocities but still showed signs of fairly high pressure. Shortly after it started happening on my second barrel, Mike Rock told me it was from severe throat erosion and severe heat checking. He said those will actually increase friction on the bullet dramatically and that is where my high pressure was coming from. A trip to the smith and look through the borescope confirmed his statements. It was bad. Really bad. It can happen VERY fast in a barrel chambered in 300 RUM. Especially if you run top end loads. In my experience, top end loads in 300 rums even without pressure signs initially, kill barrels and fast. I know thats not what you were hoping to hear and I hope I'm wrong but that's most likely the problem. Factory barrels can sometimes hold up better IMHO. They're often hammer forged and subsequently very durable and so rough they can actually improve before going downhill. With a top end fine custom barrel, they have ONLY one way to go. That is downhill. You can't typically improve a good custom bore. They're their best for only one shot. That's their first. They start going downhill after that. The hotter the caliber and the harder you run them, the faster they decline. It's not at all uncommon for the 7mm RUM and 300 RUM customs to go south short of 100 rounds. I get PMs occasionally about how fast one went south. I used to preach my feelings on this matter a lot and caught a lot of flame for it here. Guys not wanting to catch flame would pm me and say yup! You were right! In this case I truly HOPE I am wrong. M EDIT: I almost forgot, make sure there is no carbon ring present either. I'm just guessing here but it doesn't sound like you have enough rounds down it to be a carbon ring but a carbon ring will generate a lot of extra pressure and if not corrected quickly, can kill your barrel as well. [/QUOTE]
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Need help troubleshooting 300 RUM pressure issue.
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