Vihtavuori Temp Sensitivity?
- Thread starter xdeano
- Start date
Donovan, very interesting. I'm not seeing that but then I only have one chrono and no pressure trace equipment. The only case that I shoot N-540 in is a 300 SAUM with a 165 Sierra spbt. According to my log I worked up the load in 70 degree temps and tested it again at 5 degree, which is about as cold as my old bones can take. My chronoed velocities only changed 25 fps. and POI didn't change on target. It's also a very clean burning powder. I have seen hugh changes in velocity however with H-414 out of a cheetah as much as 105fps froom 90Degrees to 30degrees, so I'm guessing you're probably correct. The best solution is to use the chrono and adjust accordingly with the powder that works the best in your particular rifle.
Well the only reason I ask this question is that I've been shooting Hodgdon Varget with temperature extremes up here in North Dakota, I see quite a bit of both velocity and pressure changes. I am just looking for a powder that is even better suited to temperature extremes. I work/shoot in temperatures of -30 to 100, these are the extremes in every ones book. Granted these temperatures aren't met within a single day, but during the spring and fall my temps could vary 30 to 40 degrees.
I'm pushing the 155's at 2900fps. @ 75 degrees F.
So knowing this would I be better suited with Varget or VV N540?
Thanks guys I appreciate it.
xdeano
I'm pushing the 155's at 2900fps. @ 75 degrees F.
So knowing this would I be better suited with Varget or VV N540?
Thanks guys I appreciate it.
xdeano
xdeano.
The VV N540 may be worth a try in your .308. I would describe the N540 as very forgiving in my 6mm BR compared to Varget. By that, I mean that the vertical outside the nodes is not as pronounced as it is with Varget. I am not sure why, but there is a sweet spot a couple of tenths of a grain wide with the Varget and the vertical opens sharply on both sides of this node. Varget gives very tight vertical but in a very narrow velocity range. The N540 gives me about 50-100fps more velocity without pressure signs and the difference in vertical across a range of powder charges is much less pronounced than it is with the Varget. The best vertical is about the same with both. Nodes continue to be present but the vertical dispersion outside the nodes is less pronounced. Although I am early in my load development, I am seeing the same behavior with N560 in a .284 Shehane. I wish I had Donovan's pressure trace, but it appears to me that that Varget is providing a sharper, harder force while the N540 spreads the pressure out a bit more. QuickLoad says that N540 in a .308 Win will burn 100% of the powder in barrels as short as 20 inches.
The VV N540 may be worth a try in your .308. I would describe the N540 as very forgiving in my 6mm BR compared to Varget. By that, I mean that the vertical outside the nodes is not as pronounced as it is with Varget. I am not sure why, but there is a sweet spot a couple of tenths of a grain wide with the Varget and the vertical opens sharply on both sides of this node. Varget gives very tight vertical but in a very narrow velocity range. The N540 gives me about 50-100fps more velocity without pressure signs and the difference in vertical across a range of powder charges is much less pronounced than it is with the Varget. The best vertical is about the same with both. Nodes continue to be present but the vertical dispersion outside the nodes is less pronounced. Although I am early in my load development, I am seeing the same behavior with N560 in a .284 Shehane. I wish I had Donovan's pressure trace, but it appears to me that that Varget is providing a sharper, harder force while the N540 spreads the pressure out a bit more. QuickLoad says that N540 in a .308 Win will burn 100% of the powder in barrels as short as 20 inches.
Donovan,
Thanks for your comments. I really have to get myself one of those pressure trace devices. I keep looking at the RSL but haven't rationalized it enough yet.
Getting back to xdeano's question, it is those wide nodes that makes me think that N540 might work for him. It seems like the temperature range he wants to shoot in is bound to move him out of whatever nodes he can identify with any powder, especially in the Mountain West with the wide range of temps within a single day let alone a whole season, but, with the N540 in the 6mm BR, the vertical precision in my gun would have been very satisfactory for hunting use in or out of the nodes even out to 1000 yards.
Your comments about control of neck tension, powder charge and seating depth are also very consistent with what I experienced with the 6mm BR and N540 although I can't offer the same comparison because I had given up on Varget by the time I started working on those.
The biggest single improvement in ES and SD came when I started using one of Ken Light's annealing machines. I had already done my best with all of the other stuff like bullet pointing, concentricity, charge weight and neck thickness, but my best vertical came after I started annealing and finding the right seating depth. I haven't worked with enough chamberings to know that some are more sensitive to one thing or another, but I hope all of these things will work as well with the N560 in the 284 Shehane as they did with the N540 in the 6mm BR. So far, so good.
Thanks for your comments. I really have to get myself one of those pressure trace devices. I keep looking at the RSL but haven't rationalized it enough yet.
Getting back to xdeano's question, it is those wide nodes that makes me think that N540 might work for him. It seems like the temperature range he wants to shoot in is bound to move him out of whatever nodes he can identify with any powder, especially in the Mountain West with the wide range of temps within a single day let alone a whole season, but, with the N540 in the 6mm BR, the vertical precision in my gun would have been very satisfactory for hunting use in or out of the nodes even out to 1000 yards.
Your comments about control of neck tension, powder charge and seating depth are also very consistent with what I experienced with the 6mm BR and N540 although I can't offer the same comparison because I had given up on Varget by the time I started working on those.
The biggest single improvement in ES and SD came when I started using one of Ken Light's annealing machines. I had already done my best with all of the other stuff like bullet pointing, concentricity, charge weight and neck thickness, but my best vertical came after I started annealing and finding the right seating depth. I haven't worked with enough chamberings to know that some are more sensitive to one thing or another, but I hope all of these things will work as well with the N560 in the 284 Shehane as they did with the N540 in the 6mm BR. So far, so good.
Wow, very good input guys. I really appreciate the time you've taken to get back to me. Great discussion. I will have to give a few pounds of N540 a try here this spring to see if it can handle what I will be throwing at it. What I want is a powder that I can go shoot in the morning when it's cool and have the same powder to shoot in the afternoon/evening when it's warmer and not have to compensate 2 MOA at 800yds for every 30 degrees in temperature variance. Because 2 MOA for me would mean a miss, and a miss with what I do is not good day.
I'm just looking to take a few variable out of the equation, or at least reduce them.
Thanks guys for the help, I appreciate it.
Donovan, I'll send you an email asap.
Deano
I'm just looking to take a few variable out of the equation, or at least reduce them.
Thanks guys for the help, I appreciate it.
Donovan, I'll send you an email asap.
Deano
TonyR, Any luck finding any IMR-7828ssc?
You can also keep a check on temperature vs pressure variences on Q.L. via the same button used to access and adjust the burn rate. The button at the top, hand holding a pencil ) will open another tab near the bottom of the page, looks like a thermometer ) Once this button is clicked you can change the temperature to match your shooting conditions and see the predicted effect the program has on your selected powder. Again the data becomes more accurate once you have callibrated the program to your specific lot of powder, and this feature helps to refine this process even more. Every little variable I can eliminate is one step closer to another headache around the corner. LOL!!!
I'm back in the world of the employed after 5 months, so very little range time. Keep us in the loop.
Jon
You can also keep a check on temperature vs pressure variences on Q.L. via the same button used to access and adjust the burn rate. The button at the top, hand holding a pencil ) will open another tab near the bottom of the page, looks like a thermometer ) Once this button is clicked you can change the temperature to match your shooting conditions and see the predicted effect the program has on your selected powder. Again the data becomes more accurate once you have callibrated the program to your specific lot of powder, and this feature helps to refine this process even more. Every little variable I can eliminate is one step closer to another headache around the corner. LOL!!!
I'm back in the world of the employed after 5 months, so very little range time. Keep us in the loop.
Jon
Hi Jon.
I did find it at Powder Valley and Grafs. I ordered some and hope to test it sometime this month. I have been playing around with it in QuickLoad and I am anxious to see if it will give me the 15fps you mentioned because that might just get me up to the next node. Worth a try anyway. I am testing a number of powders in the Shehane and will post something when I have a bit more data. I have been testing in the 40-70 degree range for the last couple of months, but I will have a chance to get some results in the 90-100 degree range this month. It should be interesting.
Thanks again for the suggestion.
I did find it at Powder Valley and Grafs. I ordered some and hope to test it sometime this month. I have been playing around with it in QuickLoad and I am anxious to see if it will give me the 15fps you mentioned because that might just get me up to the next node. Worth a try anyway. I am testing a number of powders in the Shehane and will post something when I have a bit more data. I have been testing in the 40-70 degree range for the last couple of months, but I will have a chance to get some results in the 90-100 degree range this month. It should be interesting.
Thanks again for the suggestion.
Talon Manufacturing in Paw Paw West Virginia,no longer in business) in conjunction with famed Marine Sniper Carlos Hathcock manufactured Hathcocks own 'Whiter Feather' ammo. Specs were IMI brass headstamped PAW Match /CCI BR2/ 43.9 grains of N540/ Sierra 175 grain Match King. Stuff shot lights out. I have one or two boxes left that I saved for it's collector value. Wish I'd have saved more, but who knew? Boxes were plain white with Hathcock's White Feather logo in black.
As to pressure, I shot it in all kinds of temperatures without a problem. One thing people always told me it sure sounded different than Varget.
Danny
As to pressure, I shot it in all kinds of temperatures without a problem. One thing people always told me it sure sounded different than Varget.
Danny
Hi deano, I only have experience with VV560, I run it in my 1000yd gun in the upper pressure window .. I summer i use 78.0 gns of 560 and in winter it's 78.6 ..Because it's a tensioned barrel gun the grouping does not suffer much if it's too much powder for the temp,but the cases do..JR..Jeff Rogers
xdeano said:
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