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140g NBT @ 800 yards

 
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  #1  
Old 02-02-2007, 11:43 AM
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140g NBT @ 800 yards

Alright heres the deal guys, I have a great load worked up using the 140g NBT and RL-22 in my 7 RM giving consistent 3250-3275fps and 1/2 MOA grouping at 100-200-400 yards so far. I went shooting the other day and wanted to zero my 140's as I was going to start using them up on yotes and rocks etc..It was cold, about 30-32 degrees, im around 700ft above sea level. I got my crony and rifle set up at 200 yards to check velocity and accuracy, and also to zero at 200 yards instead of 100. First couple shots were little bit off due to being sighted in with different bullets, but were within an inch of each other. I adjusted the scope and put 2 shots within an inch dead center, maybe 1/4" above. Velocity was very close on this outing giving something like 3275, 3276, 3282. Couldn't really figure it out because when I worked up this load it was in the fall around 60-70 degrees and only produced 3250fps on couple different outings, so dont know whats up there. Anyways I got everythign zeroed, rifle checked for velocity, now pack everything back up and drive back to 800 yards and work on the 15" square gong. According to Nosler, the 140g NBT has a BC of .485, all I can say is I wish that was the case, but I dont think so...According to my program, I needed to have 59 clicks or so, or 15 MOA "UP" to be dead on at 800 from my 200 yard zero. I had my dad as a spotter, I dialed up 59 clicks, there was very little to no wind so I left it alone for now. First shot was way way low, no surprise there I thought. Might have pulled a little, cold bore shot..shot #2 landed in the same spot. My dad said it appeared to be about 5-6 feet low. I ended up having to add 3.5 MOA or about 14 clicks more to be dead on at 800. Anybody got any ideas as to whats going on?? I didn't think it would be that far off, but if I drop the BC down to even .400, its still doesn't match up at all. I know the BC of the 140g BT cant be in the .3's. Pressure doesn't really seem to have that much of an effect on things looking at the ballistic side of things, maybe a couple clicks yes, not 12-14!! Could it be the cold air, low elevation?? I dont know, I'm stumped, but I've noticed a lot lately that at 800 yards, I"m shooting anywhere from 2-4 MOA low with various comboes. I'm zeroing at a known distance, with known velocitys, so just dont know what else could be wrong for it to be that far off!? BTW, after noting where I needed to be click wise, hitting the 15" plate was piece of cake. NOthing substitutes getting out in the field and shooting, cant rely on the good ol computer for everything...
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Old 02-02-2007, 11:54 AM
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Re: 140g NBT @ 800 yards

According to my program, BC would have to be around .350 for me to be 73-74 clicks "up" at 800. I dont believe the BC to be that low, but who knows...??
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Old 02-02-2007, 12:44 PM
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Re: 140g NBT @ 800 yards

I have shot those bullets out to 700 yards many times and never have had a problem with the bc being low. What kind of Chronograph do you have? I suspect that is where the trouble is. I do not see a 7mm mag getting that high of velocity with a 140gr bullet. I never was able to out of the 5 I have loaded for. A good test to see if you graph is off is to sight at 100 yards dead on then shoot at 300 yards and see how low it is. I shoot about 850ft above sea level and have shot those bullets at 600 yards when it was 20 below and was short about 2 clicks at 600 yards.
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Old 02-02-2007, 01:09 PM
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Re: 140g NBT @ 800 yards

[ QUOTE ]
Velocity was very close on this outing giving something like 3275, 3276, 3282. Couldn't really figure it out because when I worked up this load it was in the fall around 60-70 degrees and only produced 3250fps on couple different outings, so dont know whats up there.

[/ QUOTE ]

I have known other shooters to see increases in velocity with RL-22 as it gets colder. I myself have personaly seen my RL-25 loads in my 300 RUM get faster when things got colder. I havent experimented (for warm/cold purposes) enough with these powders to see if it is just certain calibers or other parameters, but plan on doing some soon. In any event, it does happen with RL-22 and RL-25 in some cases.
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  #5  
Old 02-02-2007, 01:17 PM
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Re: 140g NBT @ 800 yards

Dakor- 3250 fps is not that bad out of a 7 RM. I'm using 68.5g RL-22, nosler shows this doing 3350fps but I've nowhere been close to that. I've seen lots of data to support 140's at 3250fps. Its pretty much max load in my rifle. I just dont know why there so low at 800 yards. Cronograph I'm using is a crony set 10ft from the muzzle. It had a fresh battery and everything. I know its not the best cronograph, but it seems to work alright for me most of the time. I have it zeroed at 200, so I will just see how low she shoots at 400. Getting ready to go out right now. Only have 10 bullets left but I was going to double check 800 yard, and maybe shoot 400 yards as well. Am also going to work on seating depth for 100g NBT and IMR-4350 out of my 25-06 today. Will post results soon.
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  #6  
Old 02-02-2007, 01:25 PM
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Re: 140g NBT @ 800 yards

[ QUOTE ]
Could it be the cold air, low elevation?? I dont know, I'm stumped, but I've noticed a lot lately that at 800 yards, I"m shooting anywhere from 2-4 MOA low with various comboes. I'm zeroing at a known distance, with known velocitys, so just dont know what else could be wrong for it to be that far off!? BTW, after noting where I needed to be click wise, hitting the 15" plate was piece of cake. NOthing substitutes getting out in the field and shooting, cant rely on the good ol computer for everything...


[/ QUOTE ]

First, what kind of calculator are you using? Also, I assume you are using corect enviornmental data. Pressure, temp etc...If you go to this link http://weather.noaa.gov/index.html and you can look up what the pressure was/is at the closest airport to your shooting location. If you had unusally high pressure, and you used a default in your software, that can contribute to a BC error. Are you sure your velocity is correct. Maybee check the chrony for accuracy. 300 FPS will throw things way off. If you plug in 3000 FPS (275 FPS slower) then you come up with a trajectory closer to what you are seeing based on the factory BC.

Try a differant chrony and let us know.
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  #7  
Old 02-02-2007, 02:21 PM
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Re: 140g NBT @ 800 yards

Have you double checked your scope? (clicks to MOA) Zero it at 100 then dial up 20 MOA or 80 clicks and shoot at the same spot on your target. It should be 20" higher or really close.
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