#1
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What powder scales do you guys use?
I have been working up a load for a Mach IV shooting 37 grain bullets and VihtaVouri N135 powder. I generated a graph of veloctiy versus powder charge and discovered it was totally linear over the range of velocities I tested (3150 fps to 3550 fps). I was concerned by my extreme velocity spreads (ES) which were huge compared to what I am used to in my other (larger) calibers. Anyway, based on the data, I discovered something I did not realize. I used an Ohaus Navigator digital scale which is accurate to .05 grains. Well, .05 grains translates to 18 fps! If I assume my weights are actually +/-.05 grains, that means the best I can hope for is an ES of 36 fps!! If one were using a typical reloading scale that is +/- .1 grains, the ES would be 72 fps!!!
There seems to be 3 granules of powder per .05 grains which means that each little granule of powder represents 6 fps! With this scale, the powder contribution to velocity extreme spread in my other calibers is around 2 fps and the other say 20 fps is due to other things. If I assume the "other things" are the same, my ES would be around 56 fps which is what I am seeing. What scales are you guys using? It seems that I have to invest in a scale accurate to .01 grains which would get my velocity spread due to powder charge down to under 5 fps. I realize that a high ES is not usually a problem with small calibers but with this 37 grain bullet at 3500 fps, the ballistics (and my field verification) tell me I can realistically shoot to 800 yards. At that range, a high ES generates significant vertical. I have field tested (on non-living targets) and one version of the bullet holds to the click chart to 750 yards. Another version of the bullet holds to the chart out to 900 yards. I have also observed the vertical I expected due to the high ES so I have to get it down. This spring and summer, I hope to determine what the maximum distance at which I can dispatch a groundhog. |
#2
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So how does it group??
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#3
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I use an RCBS ChargeMaster 1500 to throw the charge and then do the final weighing on my Denver Instruments MXX-123 digital scale. This scale is supposed to be accurate to within .02 grains.
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Catch ya L8R--Silverfox NRA Life Member |
#4
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Just ordered one of those Denver Instruments MXX-123 digital scale from James over at GGVG board. Hopefully it will be in soon.
Larry
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There are three kinds of men: The one that learns by reading... The few who learn by observation... And the rest, who have to piss on the electric fence for themselves...!! |
#5
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I've been using a Ohaus balance beam since about 1960. Still perfect.
Same as RCBS is sellin now for $100 or so. Paid $20 for this one back then.
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George "Gun Control is NOT about guns, it's about CONTROL!!" |
#6
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Actually, it groups pretty welll so far. My last two 10 shot groups were close to .7 at 100 yards which might sound bad but, in each case, 8 shots formed a high .3s and each had 2 fliers.
I shot an 6 shot string at a rock at 900 yards the other day to test my theory about the ES being way too high. 4 of the shots were right there but the other 2 dropped off 6 clicks (1.5 minutes) which translates to around 13.5 inches. That value pretty well corresponds to what I would expect based on the ballistics programs and my velocity extreme spread. I am very happy with the rifle at this point, I just want to try and address the extreme spread issue in case it turns out that my range on groundhogs is 700 yards instead of the 350 yards I was used to with my .17 Remington and lighter bullets. |
#7
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Denver Instruments
I too am having the ES problem. I use an Ainsworth "Accurate Load" from DI. Used it as a commercial loader for many years. Very accurate but only to one tenth. My major complaint is with DI. The return spring on the tare bar gave out and DI charged me $225.00 to replace it. Plus shipping! They also have a $50.00 minimum for anything they sell or do. The best scale I have ever used is the Ohaus Triple Beam. Still have it but it is sloooow.
1939 Admiral Isoroku Yamamoto: " You cannot invade the mainland United States. There would be a rifle behind every blade of grass"!! |
#8
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#9
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I am glad you said that Jim.
Doug, I have posted and deleted a couple of times trying to figure the right way to say this. I can't find a delicate way so I will just lay it on the line, good, bad or otherwise In short I think you are barking up the wrong tree here. If you are concerning youself with 0.05 or less grains of powder to get the rifle to do what you want I think something is amiss. No matter how accurate your powder is weighed out and how well the brass is detailed if the load isn't tuned right your extreme spreads will not come down to single digits like you are after, the powder needs to be burning optimally to get the spreads nice and low regardless of how precise everything else is. The powder needs a certain pressure level to really burn perfectly and you mayt well not be at that pressure level. I think that if your velocity vs powder weight chart is a straight line you probably haven't gone hot enough to get the pressure to peak which will help the powder burn optimally which will cut the velocity spreads. If it is a straight line relationship I think you haven't reached maximum since at some point the velocity increase should slow with added powder, until that happens you may have not gone far enough ?????? Maybe .... tread carefully. I am not saying that you MUST load to MAX pressure but you likely will need to be close to it to get things working nicely. WIth that straight line you may not have go that far yet ??? Maybe you need to explore different powders as well. 37 grain VLD's in a 17 Mach IV isn't what every man and his dog is using so you might well need to look at a number of options to try and achieve your goal, which is stretching the concept somewhat !! Also, it if can't keep ten shots inside 0.7 at 100 yards it is at a distinct disadvantage at 900 or so right from the get go. That nice cluster in the middle is irrelevant if you can't get the fliers out of the equation, logically any flier from a main cluster at 100 will be well wide of the mark out at the distances you are trying to shoot. I think you want WAAAY better accuracy than that regardless of what velocity spreads you have. Sorry to sound so negative, just trying to offer something that might help. |
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