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Long Distance Shooting Discuss tools, techniques, tips and theories of long distance shooting |
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#1
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Muzzle velocity and temp powder
If i have 4fps of variance between 0* & 125* would i enter 4fps for my variance? How does that compute per degree of change?
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U.S. Army Combat Engineer |
#2
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Is this what you actually measured? It would likely be quite a bit more even with varget- (a continuation of that thread I guess?)
I dont recall, but I think from 35 deg to 110 deg I noticed a MV change of about 40-50. However, if you reload, and you shoot 10 rounds through a chronograph, your ES (extreme spread) from slowest to fasted will all depend on your anal retentiveness... My ES is in the mid 20's FPS which is fine for most practical shooters though BR guys would scoff unless they hit single digits. So- Consider that- your ES on the same day, same ammo has a ES of 25+ FPS... And you want to learn how to plot a 4 fps difference? Even BR guys dont get an ES of 4 fps with 10 rounds unless Lynn Jr tells me I'm wrong. Simple approach is to have 3 charts (if you normally shoot at the same location) 1 for for cold weather, 1 for moderate and one for hot weather. If you have an "in between" weather day- look at the 2 charts and split the middle. Once again, your true issue is the Density Altitude. And a Kestrel and shooter app will cover those- and you can can also plug in your expected MV correction from temp conditions. |
#3
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Sorry dinner time. Short answer is definately not 4fps. Im seeing 5.45fps difference per every 1*.
When dinner is over ill revisit. I like your explaination.
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U.S. Army Combat Engineer |
#4
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personally 4fps gets chalked up as a wash. In perspective, put into your calculator your velocity and right down your drop at 100 yards and at the max range of your firearm, do the same with the velocity +4fps, i highly doubt you can shoot the different.
example my 308 my standard load @1k has a drop of 294.5 @1500 - 943.8 +4fps @1k - 293.6 @1500 940.6 so 1 inch at 1k your talking 1/10 of 1 MOA. if you're that accurate kudos! |
#5
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I think all of this extended thinking is hurting my brain and making my formula muddied. I think i need to log some more data and go back to a traditional chart like suggested above before i revisit trying to adjust it automatically instead of manually.
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U.S. Army Combat Engineer |
#6
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My es is the same 20-25fps difference but i only use the avg for figuring out anything.
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U.S. Army Combat Engineer |
#7
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To be honest I only run 1 chart for moderate weather... it's of such minor significance. |
#8
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__________________
U.S. Army Combat Engineer |
#10
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Also, the chart you posted on the other thread shows 168 SMK... for longer distances, people either use the 175 SMK or the hornady 177 (very similar higher BC than the 168) or the VLD for longer range.. which personally I dont like the VLD since they want to be jammed into the lands... unloading a live round becomes problematic.... round sticks in rifling, brass pulls out.. dumping powder in your action and need a cleaning rod to knock out the bullet.... Seen it happen about 4 times.....
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#11
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I use both 168gr and 175gr. 168gr (600 under) 175gr (600 over) im just currently using 168gr right now. I had to temporarily stop using 175gr as they kept unseating as you experianced with vld. I also have a 6.5 creedmoor running 140gr amax.
__________________
U.S. Army Combat Engineer |
#12
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Its definately not fun trying to clean out all the powder from the chamber and then rod out the bullet.
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U.S. Army Combat Engineer |
#13
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I always start .005 off the lands and start playing with it from there. I,ve had loads that wouldn't shoot worth a damn until i gave it 1/8" of free bore. Last edited by kcstott; 01-20-2015 at 7:20 AM.. |
#14
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It's very common that smk shoots well with a 25-30 thou jump. It's very common the VLD doesnt shoot well until it's jammed into the lands. I do not and never have shot VLD's but have seen others using them that jam the lands and had to unload.... and have seen them pull apart 4 times now. Currently swapped my 308 for a 6.5 creed with hornady Amax 140 with a 15 thou jump. VLD specifically is known to tighten up groups when jammed into the lands- no others I recall. |
#15
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If thats true it sucks, as that severely limits your powder charge ability. |
#16
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There's room for the powder. But when playing with jamming, you need to back off the powder charge so you dont get a dangerous pressure spike. The real problem is magazines that will hold these LONG rounds... Hence, most of these people run AICS mags that allow a longer COAL.... and an aftermarket barrel with a tight chamber since factory barrels tend to be long in the throat. And, to be honest, I forgot if the actual jammed bullets were berger VLD, or Lapua Scenar.... but it's one of those 2 that shoot better jammed into the lands. In retrospect, I think its the scenar.... But, as I said... never played with them- dont see the point of that hassle. |
#17
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It's common to jam Berger VLDs, but they also work in jump. You really have to work their seating depth either way though. I think the myth that they have to be jammed is based on the fact that it's a lot easier than doing all the load dev to find out where they want to be jumped in your rifle.
I don't love VLDs, especially with Hybrids, and A-Max bullets which are way more flexible without much BC loss. Everyone I know who runs jammed are single loading in some sort of long range match. It's a last .0001% sort of shooting that makes me think such loading is worth it, unless it's to make an old torn up millsurp rifle perform better, which I've not had to do but heard about it.
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weg: That device is obsolete now. They replaced it with wizards. frank: Wait a minute. There are more than one wizard? Is [are?] the wizard calibrated? |
#18
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Thats what I mean with the pressure spike. When we were doing our mile shot with a 300 win mag and 220 gr SMK I was seeing the primer just start to crater and flatten out with the bullet just off the lands. I backed the bullet off the lands even further and the pressure signs never went away but never got worse.
ended up using just over starting load and .030" off the lands. that seemed to print nice little groups Last edited by kcstott; 01-24-2015 at 1:49 PM.. |
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