Posted: 3/7/2016 12:59:03 PM EDT
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I am having over pressure problems with ammunition that I am reloading for my Remington 700 Police. The only thing that I can figure to do is to scrap all of my brass and start over fresh. If anyone has any other ideas I would be all ears. I did not have a chronograph with me yesterday, so I didn't get any velocity readings.
Load 1. Backing out primers 38gr IMR 4064 LC LR 07 Hornady 178GR BTHP COAL 2.80 Winchester Large Rifle Primer Load 2. flattening primers 38.5gr IMR 4064 LC LR 07 Hornady 178GR BTHP COAL 2.80 Winchester Large Rifle Primer. I had two other loads worked up at 39 and 39.5gr but I did not shoot them. |
| It does seem like a light load. I am loading 42.5 gr. 4064 under a 175 Nosler CC in WCC14 brass with no pressure signs. My rifle does have a long throat as I can't even seat long enough to get anywhere close to the rifling so that probably helps with the pressure a little. |
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Seems like 38gr is low enough that the case grips the chamber walls and the primer backs out to the bolt face. 38.5gr is just high enough to push/stretch the case back to the bolt face, which flattens the primer. Make sure your headspace is snug. I prefer using Redding Competition Shellholders to adjust headspace: http://redding-reloading.com/online-catalog/35-competition-shellholder-sets, starting with the +0.010" and working down until the cases chamber and extract with very little to no resistance. Then perhaps try a higher charge - about 42gr according to Hodgdon. |
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How was the bolt lift? How old is the powder? My old QuickLoad shows 40gr charge of IMR4064 with 55gr case capacity to be 100% load density. 38.5 gr is 98% and 47k psi I can't see that being too low.
Newer lots must have a different density if people are using 42gr charges. If you mean the ejected round had a primer that was above flush then I would agree you are too light. Primers are suppose to back out to flush. If it's farther than that, the case isn't expanding back against the bolt face. That being the case i don't think you are having over pressure. If bolt lift and extraction were easy it is a pretty good bet you are not too high of pressure. |
| I am one that also agrees it might be too low of a charge. I use 42.7 topped off with the 178 hpbt with LC and Hornady mat ch ( same capacity as LC) through a semiauto with no problems. I would start around 40 or 40.5 just to see. Or have the rifle I specter by a smith to make sure remington did screw the pooch when making that rifle. |
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I had a very similar problem.
I tried 38 through 42.5gr IMR 4064, 165gr SST, LC brass, Win LR primers. 2.805 COAL. At 41.5gr, primers were flat as shit and extractor was ripping through rims. I had to reduce my powder charge to 39.5 to get this load to function in my rifle and those are only going 2225-2240 FPS. Last weekend I pulled down the last few I had loaded up with IMR and tried Varget. Same brass, same primer, same bullet (for the work up)--I went from 41gr-45gr with no signs of overpressure. The 43.9gr with 168 HPBTM load that shoots the best for me is flying at 2550. I think we got a bad batch of 4064. (I bought mine in Dec '15) I'm just glad I only bought 1 lb because I'm not using it again. |
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Both of your loads are TOO LOW, This causes secondary pressure spike which is VERY dangerous. See: https://www.shootingsoftware.com/barrel.htm No pictures, no replies from op on bolt lift so who knows but I don't think he is seeing high pressure. His load density and pressure should be high enough. I find it very hard to believe he is seeing secondary explosions. I don't use load data for most of my loads and I have to work up. I start with 80-85% load density sometimes pressures as low as 45kpsi( as measured by the equipment from the page you posted). I have never seen the pressure traces shown on that page. Now obviously different powders etc. behave differently. If he is getting high pressure it should show itself in bolt lift, swipes and/or extraction problems. |
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No pictures, no replies from op on bolt lift so who knows but I don't think he is seeing high pressure. His load density and pressure should be high enough. I find it very hard to believe he is seeing secondary explosions. I don't use load data for most of my loads and I have to work up. I start with 80-85% load density sometimes pressures as low as 45kpsi( as measured by the equipment from the page you posted). I have never seen the pressure traces shown on that page. Now obviously different powders etc. behave differently. If he is getting high pressure it should show itself in bolt lift, swipes and/or extraction problems. Quoted:
Quoted:
Both of your loads are TOO LOW, This causes secondary pressure spike which is VERY dangerous. See: https://www.shootingsoftware.com/barrel.htm No pictures, no replies from op on bolt lift so who knows but I don't think he is seeing high pressure. His load density and pressure should be high enough. I find it very hard to believe he is seeing secondary explosions. I don't use load data for most of my loads and I have to work up. I start with 80-85% load density sometimes pressures as low as 45kpsi( as measured by the equipment from the page you posted). I have never seen the pressure traces shown on that page. Now obviously different powders etc. behave differently. If he is getting high pressure it should show itself in bolt lift, swipes and/or extraction problems. I had many of the problems he wrote about when I was shooting 308W using 155 SMKs with 42 gr Varget. The problems went away when I moved up the charge weight scale. I ended up at 47.8 gr Varget and 155 Scenars with no pressure signs. Yet I had all these symptoms at 42 gr. |
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Quoted:
I had many of the problems he wrote about when I was shooting 308W using 155 SMKs with 42 gr Varget. The problems went away when I moved up the charge weight scale. I ended up at 47.8 gr Varget and 155 Scenars with no pressure signs. Yet I had all these symptoms at 42 gr. Quoted:
Quoted:
Quoted:
Both of your loads are TOO LOW, This causes secondary pressure spike which is VERY dangerous. See: https://www.shootingsoftware.com/barrel.htm No pictures, no replies from op on bolt lift so who knows but I don't think he is seeing high pressure. His load density and pressure should be high enough. I find it very hard to believe he is seeing secondary explosions. I don't use load data for most of my loads and I have to work up. I start with 80-85% load density sometimes pressures as low as 45kpsi( as measured by the equipment from the page you posted). I have never seen the pressure traces shown on that page. Now obviously different powders etc. behave differently. If he is getting high pressure it should show itself in bolt lift, swipes and/or extraction problems. I had many of the problems he wrote about when I was shooting 308W using 155 SMKs with 42 gr Varget. The problems went away when I moved up the charge weight scale. I ended up at 47.8 gr Varget and 155 Scenars with no pressure signs. Yet I had all these symptoms at 42 gr. But was it high pressure or low pressure? Hard bolt lift, swipes, difficult extraction or backed out primers? If a primer backs out beyond the case head that would suggest low pressure not a high pressure secondary explosion. |
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Quoted:
But was it high pressure or low pressure? Hard bolt lift, swipes, difficult extraction or backed out primers? If a primer backs out beyond the case head that would suggest low pressure not a high pressure secondary explosion. Quoted:
Quoted:
Quoted:
Quoted:
Both of your loads are TOO LOW, This causes secondary pressure spike which is VERY dangerous. See: https://www.shootingsoftware.com/barrel.htm No pictures, no replies from op on bolt lift so who knows but I don't think he is seeing high pressure. His load density and pressure should be high enough. I find it very hard to believe he is seeing secondary explosions. I don't use load data for most of my loads and I have to work up. I start with 80-85% load density sometimes pressures as low as 45kpsi( as measured by the equipment from the page you posted). I have never seen the pressure traces shown on that page. Now obviously different powders etc. behave differently. If he is getting high pressure it should show itself in bolt lift, swipes and/or extraction problems. I had many of the problems he wrote about when I was shooting 308W using 155 SMKs with 42 gr Varget. The problems went away when I moved up the charge weight scale. I ended up at 47.8 gr Varget and 155 Scenars with no pressure signs. Yet I had all these symptoms at 42 gr. But was it high pressure or low pressure? Hard bolt lift, swipes, difficult extraction or backed out primers? If a primer backs out beyond the case head that would suggest low pressure not a high pressure secondary explosion. In my case: it was hard bolt lift, a bit of hard extraction, completely flattened primers, almost no hint of primer back outs--because I was setting the shoulder to have less then 0.003 of clearance in the chamber. The gun also had a sharp high pitched report way different than when the pressures went up with more powder. |
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Quoted:
In my case: it was hard bolt lift, a bit of hard extraction, completely flattened primers, almost no hint of primer back outs--because I was setting the shoulder to have less then 0.003 of clearance in the chamber. The gun also had a sharp high pitched report way different than when the pressures went up with more powder. Quoted:
Quoted:
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Quoted:
Both of your loads are TOO LOW, This causes secondary pressure spike which is VERY dangerous. See: https://www.shootingsoftware.com/barrel.htm No pictures, no replies from op on bolt lift so who knows but I don't think he is seeing high pressure. His load density and pressure should be high enough. I find it very hard to believe he is seeing secondary explosions. I don't use load data for most of my loads and I have to work up. I start with 80-85% load density sometimes pressures as low as 45kpsi( as measured by the equipment from the page you posted). I have never seen the pressure traces shown on that page. Now obviously different powders etc. behave differently. If he is getting high pressure it should show itself in bolt lift, swipes and/or extraction problems. I had many of the problems he wrote about when I was shooting 308W using 155 SMKs with 42 gr Varget. The problems went away when I moved up the charge weight scale. I ended up at 47.8 gr Varget and 155 Scenars with no pressure signs. Yet I had all these symptoms at 42 gr. But was it high pressure or low pressure? Hard bolt lift, swipes, difficult extraction or backed out primers? If a primer backs out beyond the case head that would suggest low pressure not a high pressure secondary explosion. In my case: it was hard bolt lift, a bit of hard extraction, completely flattened primers, almost no hint of primer back outs--because I was setting the shoulder to have less then 0.003 of clearance in the chamber. The gun also had a sharp high pitched report way different than when the pressures went up with more powder. Yeah, no doubts there. |
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1. problem one is you are likely pushing your shoulders too far back for your particular chamber. Your short case is being held forward by the ejector. When you fire it the primer comes rearward to the bolt face. The rest of the case comes a millisecond after either reseating the primer making it look like over pressure or not even seating it all the way. This is also how you get your brass to stretch out for a case head separation, Remedy; find out your chamber length, load your brass so that it is only 3 or 4 thousands of free headspace. If your chamber is 1.631" loading to 1.628 or so is about right. I am guessing you may be looking at much more of a gap in your current setup.
2. Increase charges a little farther up. ETA, with a 4 grain between start and max spread there is no need to reduce that far. http://www.imrpowder.com/data/rifle/308win-2005apr03.php IMR data uses Winchester cases. I would expect you to find a decent load around 40.5 to 41.5. There is another accuracy node farther up but that one may likely give you the pressure signs you are worried about. |
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Cheap electronic powder scale? This could be causing your problem, you aren't actually weighing charges accurately. Try a set of scale weight checks.
Too much headspace when combined with light loads can cause the primer to back out. Your rifle's headspace may be fine, you're just resizing the brass too much. If you have a bolt action remove the firing pin and ejector and resize the brass so the bolt just closes without resistance. Or buy Hornady's Lock-N-Load case headspace gage system and adjust your dies for a minimum of .0015" clearance on a bolt action, .003" minimum clearance on a semi-auto. 41.5 grains of IMR-4064 is a maximum charge when using Lake City brass and 168 grain Sierra Match Kings. I would consider 41.0 grains of IMR-4064 as a maximum charge when loading 175 grain Sierra Match Kings in Lake City brass. Look at 2500 fps as maximum from a 20" barrel and 2600 fps as maximum from a 24" barrel with either bullet. Look at 2450 fps from a 20" and 2550 fps from a 24" barrel when shooting Hornady 178's as a safe working maximum. Try different primers if all else fails. |