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Velocity Jump on new barrels
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<blockquote data-quote="Gamesniper19" data-source="post: 1538635" data-attributes="member: 95013"><p>NZ. I agree with much of what you said although I would have to review the data on your point around "a velocity increase always comes with a commensurate pressure increase" before I agree 100%. For the rest of my comments, I am not including factory barrels...the build with them is so inconsistent I dont think it is even fair to hold them accountable to a custom barrel application. I agree with what you said about how they are built and if we are talking full custom rifles with high quality barrels, factory barrels are a non-issue.</p><p></p><p>Yes, the rationale you stated, especially barrel fouling and increased friction can cause increases in pressure. <strong><em>We do need to clarify what is an increase in pressure.</em> </strong>Some normal increases are due to the cocktail we choose to run. According to military testing with 308, a change of pressure from 4 different component mixes, using the exact same bullet and powder weights, saw chamber pressure differences from 45000 CUP all the way up to 53600 CUP. In some cases, the velocity difference across all the metrics reviewed was as little as 15 fps and as much as 30 from step to step (50 to 100 points of pressure). Hardly a pressure increase of note. We saw the same with 264 win mag with chamber variations from 51000 and 2914 fps to 64000 cup and 3048 fps. Again with very low changes in overall pressures due to any fouling. </p><p></p><p>A barrel would have to be fouled to the point of danger to have a huge affect on pressures that would cause signifiant issues. Would velocity change, perhaps, if the fouling were so constricting to change the overall bore of the barrel. That may affect fps but I have no data to show that 100 rounds would cause that. IF that were the case, PRS and military shooters would clean their barrels every 100 rounds to stay accurate which they do not do.</p><p></p><p>That said, not all metal acts the same, and not all barrels act the same, especially carbon fiber barrels. We cannot use 100% metal barrel mentality 100% of the time with carbon fiber barrels. They act differently due to their stiffness and their ability to move heat. I am happy to discuss this at any length with anyone who would like to.</p><p></p><p>Question, What scope are you utilizing to see metal platelets? </p><p>There is data to show that barrels get smoother the more they are shot for the very reason you mentioned, continued friction and heat at such high nodes, the metal of the barrel is re-tempered at a microscopic level every time we shoot. This is what would cause the barrel molecules to "go in one direction" but it would take a 400X microscope to see that. This is also a huge factor in cleaning and barrel break in...the more you shoot, clean to bare metal, and shoot, the smoother the barrel is and the performance should subsequently be more consistent, until the barrel and chamber reaches a fail point from wear.</p><p></p><p>I am very fortunate to have first hand knowledge of the PROOF barrel testing and personally knew Jeff Lawrence, the brains behind their barrels. (PROOF bought Jeff Lawrence barrels as part of their conglomerate). According to Jeff and the research done by SOCOM, they saw increase in fps without significant pressure increases at about 80 rounds of 300 WM with PROOF barrels. (the key to that statement is what we define as significant pressure) This was seen with a clean bore, and a dirty bore. The corresponding fps increase was around 48 fps average and stabilized after about 80 rounds and was consistent through 1500 rounds. </p><p></p><p>The stated 140+ fps increase seems a bit out of range. My ask of Doug would be what measuring tool was used? Magneto speed? Have you ensured that whatever measuring tool you used, it is calibrated and reading correctly? Test it on a rifle you know is consistent to be sure.</p><p></p><p>Barrel break in is a VERY SUBJECTIVE thing. The metal of the barrel has a lot to do with it, the type of solvent and the way it is cleaned has a lot to do with it, and the abrasive/lack of abrasives have a lot to do with it. There IS NO ABSOLUTE rule for cleaning a barrel. Too many variables, was it button rifled, who lapped the barrel before and after, was it lapped at all, was it cut rifled, what grade of steel was used, how well is the reamer made and how was it chambered? For instance, Blaser uses a grade of steel so hard, they dont lap them...incorrect lapping can hurt a barrel even worse. So if that happens and you dont know it, and you use abrasives, you can make the barrel even worse.</p><p>Furthermore, if you use abrasives and aren't super careful to be very even with your cleaning, you can oval a barrel and case huge pressure and accuracy issues. When all else fails, ask the barrel maker what they recommend and go with that as your rule.</p><p></p><p>Abrasives actively remove metal in larger quantities than can be actively controlled by the vast majority of people. Professionals who lap barrels do it by feel first and visual confirmation, the average person could never achieve that so I do not recommend abrasives to the average shooter, ever.</p><p>First hand data and first hand review of bore integrity has shown me is; if your throat, specifically the first 3 to 6 inches is degraded, then you will lose accuracy. Additionally, if the last 1 to 3 inches is degraded, you will also lose accuracy. Generally, a barrel will be "burned out" in the first 6 inches and more acutely in the first 2 inches. This is one of the reasons many shooters "chase the threads" to increase barrel life.</p><p></p><p>I do not recommend the regular use of barrel abrasives unless there is a specific reason to address a specific section of your barrel (fouling, beginnings of rust or pitting). Cleaning to bare steel is what we want and you don't have to use abrasives to do that in a well made barrel. NO, you don't. Additionally, in all the barrels that I have seen, no PRS shooter that I know, no military shooter that i worked with, and the barrel makers that I talk to tell me no abrasives.</p><p></p><p>Ok....here we go <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p></blockquote><p></p>
[QUOTE="Gamesniper19, post: 1538635, member: 95013"] NZ. I agree with much of what you said although I would have to review the data on your point around "a velocity increase always comes with a commensurate pressure increase" before I agree 100%. For the rest of my comments, I am not including factory barrels...the build with them is so inconsistent I dont think it is even fair to hold them accountable to a custom barrel application. I agree with what you said about how they are built and if we are talking full custom rifles with high quality barrels, factory barrels are a non-issue. Yes, the rationale you stated, especially barrel fouling and increased friction can cause increases in pressure. [B][I]We do need to clarify what is an increase in pressure.[/I] [/B]Some normal increases are due to the cocktail we choose to run. According to military testing with 308, a change of pressure from 4 different component mixes, using the exact same bullet and powder weights, saw chamber pressure differences from 45000 CUP all the way up to 53600 CUP. In some cases, the velocity difference across all the metrics reviewed was as little as 15 fps and as much as 30 from step to step (50 to 100 points of pressure). Hardly a pressure increase of note. We saw the same with 264 win mag with chamber variations from 51000 and 2914 fps to 64000 cup and 3048 fps. Again with very low changes in overall pressures due to any fouling. A barrel would have to be fouled to the point of danger to have a huge affect on pressures that would cause signifiant issues. Would velocity change, perhaps, if the fouling were so constricting to change the overall bore of the barrel. That may affect fps but I have no data to show that 100 rounds would cause that. IF that were the case, PRS and military shooters would clean their barrels every 100 rounds to stay accurate which they do not do. That said, not all metal acts the same, and not all barrels act the same, especially carbon fiber barrels. We cannot use 100% metal barrel mentality 100% of the time with carbon fiber barrels. They act differently due to their stiffness and their ability to move heat. I am happy to discuss this at any length with anyone who would like to. Question, What scope are you utilizing to see metal platelets? There is data to show that barrels get smoother the more they are shot for the very reason you mentioned, continued friction and heat at such high nodes, the metal of the barrel is re-tempered at a microscopic level every time we shoot. This is what would cause the barrel molecules to "go in one direction" but it would take a 400X microscope to see that. This is also a huge factor in cleaning and barrel break in...the more you shoot, clean to bare metal, and shoot, the smoother the barrel is and the performance should subsequently be more consistent, until the barrel and chamber reaches a fail point from wear. I am very fortunate to have first hand knowledge of the PROOF barrel testing and personally knew Jeff Lawrence, the brains behind their barrels. (PROOF bought Jeff Lawrence barrels as part of their conglomerate). According to Jeff and the research done by SOCOM, they saw increase in fps without significant pressure increases at about 80 rounds of 300 WM with PROOF barrels. (the key to that statement is what we define as significant pressure) This was seen with a clean bore, and a dirty bore. The corresponding fps increase was around 48 fps average and stabilized after about 80 rounds and was consistent through 1500 rounds. The stated 140+ fps increase seems a bit out of range. My ask of Doug would be what measuring tool was used? Magneto speed? Have you ensured that whatever measuring tool you used, it is calibrated and reading correctly? Test it on a rifle you know is consistent to be sure. Barrel break in is a VERY SUBJECTIVE thing. The metal of the barrel has a lot to do with it, the type of solvent and the way it is cleaned has a lot to do with it, and the abrasive/lack of abrasives have a lot to do with it. There IS NO ABSOLUTE rule for cleaning a barrel. Too many variables, was it button rifled, who lapped the barrel before and after, was it lapped at all, was it cut rifled, what grade of steel was used, how well is the reamer made and how was it chambered? For instance, Blaser uses a grade of steel so hard, they dont lap them...incorrect lapping can hurt a barrel even worse. So if that happens and you dont know it, and you use abrasives, you can make the barrel even worse. Furthermore, if you use abrasives and aren't super careful to be very even with your cleaning, you can oval a barrel and case huge pressure and accuracy issues. When all else fails, ask the barrel maker what they recommend and go with that as your rule. Abrasives actively remove metal in larger quantities than can be actively controlled by the vast majority of people. Professionals who lap barrels do it by feel first and visual confirmation, the average person could never achieve that so I do not recommend abrasives to the average shooter, ever. First hand data and first hand review of bore integrity has shown me is; if your throat, specifically the first 3 to 6 inches is degraded, then you will lose accuracy. Additionally, if the last 1 to 3 inches is degraded, you will also lose accuracy. Generally, a barrel will be "burned out" in the first 6 inches and more acutely in the first 2 inches. This is one of the reasons many shooters "chase the threads" to increase barrel life. I do not recommend the regular use of barrel abrasives unless there is a specific reason to address a specific section of your barrel (fouling, beginnings of rust or pitting). Cleaning to bare steel is what we want and you don't have to use abrasives to do that in a well made barrel. NO, you don't. Additionally, in all the barrels that I have seen, no PRS shooter that I know, no military shooter that i worked with, and the barrel makers that I talk to tell me no abrasives. Ok....here we go :) [/QUOTE]
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