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Rifles, Bullets, Barrels & Ballistics
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<blockquote data-quote="Guest" data-source="post: 33829"><p>Jon,</p><p></p><p>Here is the burn rate the way that Hodgdon sees it. I've also seen it flopped. So, it's anybody's game at that point. Fast barrels, fast lot number, slow barrels, slow lot numbers. My Retumbo runs just a bit slower than the Re-25.</p><p></p><p>97. Alliant Reloder 25</p><p>98. Hodgdon Retumbo</p><p>_____________________________________________</p><p></p><p>I had to look back in my notes to see if I had written anything down regarding the shooting of one powder over another. I guess that I avoided that problem by getting good advice before I committed that error. I have a note that says never shoot a test of one powder over another without cleaning the barrel thoroughly first. The note states that this situation has the potential to create higher pressures. Needless to say, I clean my barrels before I switch powders or bullets. It's such an old habit that I don't even think about it anymore, that's why I had to look it up. The Benchrest guys have discussed this on occasion with the same answer.</p><p>_____________________________________________</p><p></p><p>I'm sure that you've seen this infomation but I thought that I would post it for some of the others if they are interested.</p><p></p><p>200 GR. BAR XFB (1.475")(Starting Loads)</p><p> DIA. .308" COL: 3.575" </p><p>RETUMBO 81.0 2852 56,200 PSI (start)</p><p></p><p>200 GR. BAR XFB (1.475")(Maximum Loads)</p><p> DIA. .308" COL: 3.575" </p><p>RETUMBO 86.0 2988 62,800 PSI (end)</p><p>_____________________________________________</p><p></p><p>V V N-170 gives good results in my 300 RUMs. </p><p>I am getting ready to start some shooting at 300 yards to see if the accuracy holds up from 200 yards. These targets were averaging about 1-3/4" for 5 shots, paced (cooling the barrel), at the 200 yard mark. There have been some exceptional targets sprinkled into the mix but they are not the norm, merely the tease. I have a bad time with wind this time of the year, it blows pretty much non-stop most of the day then the temps go up and the mirage kicks in. I'm seriously</p><p>thinking about camping out where I test and start shooting at first light which is about 5:10AM here. The wind can be fairly calm at that time of the day. Besides, the bullets that I'm shooting aren't supposed to perform well at short ranges. I had Dave Kiff grind me a reamer specifically for VLD Match bullets and a minimum throat length. I have 4 barrels that I'm working with right now, with various bullet weights.</p><p>22" / 12 twist</p><p>26" / 15 twist</p><p>28" / 12 twist</p><p>30" / 10 twist.</p><p></p><p>210 Berger VLD's @ ~3000 fps.</p><p>190 Berger VLD's @ ~3150 fps.</p><p>185 Lapua Scenars @ ~3200 fps.</p><p>_____________________________________________</p><p></p><p>You might want to do a quick test with some of your brass to see if it has any effect on pressure. </p><p></p><p> <BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR> It almost seems like that with each subsequent firing, pressure signs come on earlier and earlier. <HR></BLOCKQUOTE></p><p></p><p>Take a few pieces and anneal the necks, then reload and fire as usual. See if you notice any lessening of the signs of high pressure. I've had to do this with some other cartridges that show signs of work hardening.</p><p>_____________________________________________</p><p></p><p>It's been a long time since I worked with a factory barrel. Lapping it with JB is a good idea to smooth it out the best that you can. But keep in mind that it may just be a poor example of a factory barrel. It happens. Find someone that has a borescope or visit your gunsmith if he has one, but be prepared to reimburse him if he does and see if he will let you look through the 'scope. It's time out of his day and it is billable.</p><p></p><p>Dan Lilja doesn't recommend JB because he goes to a great effort to lap each and every one of his barrels before they leave his shop. I have never had to lap one of his barrels. On the other hand, I have had to lead lap some other brands before they could even be threaded, chambered and crowned.</p><p></p><p>That's the best that I can do for tonight. Long, but I hope a little bit helpful.</p></blockquote><p></p>
[QUOTE="Guest, post: 33829"] Jon, Here is the burn rate the way that Hodgdon sees it. I've also seen it flopped. So, it's anybody's game at that point. Fast barrels, fast lot number, slow barrels, slow lot numbers. My Retumbo runs just a bit slower than the Re-25. 97. Alliant Reloder 25 98. Hodgdon Retumbo _____________________________________________ I had to look back in my notes to see if I had written anything down regarding the shooting of one powder over another. I guess that I avoided that problem by getting good advice before I committed that error. I have a note that says never shoot a test of one powder over another without cleaning the barrel thoroughly first. The note states that this situation has the potential to create higher pressures. Needless to say, I clean my barrels before I switch powders or bullets. It's such an old habit that I don't even think about it anymore, that's why I had to look it up. The Benchrest guys have discussed this on occasion with the same answer. _____________________________________________ I'm sure that you've seen this infomation but I thought that I would post it for some of the others if they are interested. 200 GR. BAR XFB (1.475")(Starting Loads) DIA. .308" COL: 3.575" RETUMBO 81.0 2852 56,200 PSI (start) 200 GR. BAR XFB (1.475")(Maximum Loads) DIA. .308" COL: 3.575" RETUMBO 86.0 2988 62,800 PSI (end) _____________________________________________ V V N-170 gives good results in my 300 RUMs. I am getting ready to start some shooting at 300 yards to see if the accuracy holds up from 200 yards. These targets were averaging about 1-3/4" for 5 shots, paced (cooling the barrel), at the 200 yard mark. There have been some exceptional targets sprinkled into the mix but they are not the norm, merely the tease. I have a bad time with wind this time of the year, it blows pretty much non-stop most of the day then the temps go up and the mirage kicks in. I'm seriously thinking about camping out where I test and start shooting at first light which is about 5:10AM here. The wind can be fairly calm at that time of the day. Besides, the bullets that I'm shooting aren't supposed to perform well at short ranges. I had Dave Kiff grind me a reamer specifically for VLD Match bullets and a minimum throat length. I have 4 barrels that I'm working with right now, with various bullet weights. 22" / 12 twist 26" / 15 twist 28" / 12 twist 30" / 10 twist. 210 Berger VLD's @ ~3000 fps. 190 Berger VLD's @ ~3150 fps. 185 Lapua Scenars @ ~3200 fps. _____________________________________________ You might want to do a quick test with some of your brass to see if it has any effect on pressure. <BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><HR> It almost seems like that with each subsequent firing, pressure signs come on earlier and earlier. <HR></BLOCKQUOTE> Take a few pieces and anneal the necks, then reload and fire as usual. See if you notice any lessening of the signs of high pressure. I've had to do this with some other cartridges that show signs of work hardening. _____________________________________________ It's been a long time since I worked with a factory barrel. Lapping it with JB is a good idea to smooth it out the best that you can. But keep in mind that it may just be a poor example of a factory barrel. It happens. Find someone that has a borescope or visit your gunsmith if he has one, but be prepared to reimburse him if he does and see if he will let you look through the 'scope. It's time out of his day and it is billable. Dan Lilja doesn't recommend JB because he goes to a great effort to lap each and every one of his barrels before they leave his shop. I have never had to lap one of his barrels. On the other hand, I have had to lead lap some other brands before they could even be threaded, chambered and crowned. That's the best that I can do for tonight. Long, but I hope a little bit helpful. [/QUOTE]
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