140g NBT @ 800 yards

[remingtonman_25_06]

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...

 

[remingtonman_25_06]

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...??

 

[dakor]

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.

 

[Michael Eichele]

[ 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.

 

[remingtonman_25_06]

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.

 

[Michael Eichele]

[ 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.

 

[MagMan]

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.

 

[Michael Eichele]

That is a very good point MagMan. Most scopes are not a true MOA to click ratio. If it is a .250 MOA/click scope your bullet should have dropped 123.5" at 800 yards with the info you provided. If the value was in reality .200/click, this would give you 74 clicks to hit your target instead of 59 clicks.

Good job MagMan!

As was stated, a dead zero at 100 yards and 80 clicks will give you 20.94" of differance IF it is truly .25 MOA/click. If it is .200 MOA/click it iwll be 16.75" of differance.

Bear in mind that this issue could still be a combination of problems like a faulty click value and faulty chrony.

Please, let us know.

 

[Michael Eichele]

On a side note:

If you ever want to test any scope as to its real MOA/click ratio, you can use this simple formula.

Inches bullets moved from zero / number of clicks / 1.047 / (zero range/100) The answer is EXACT MOA/click values and can be done with any scope.

This formula works for any zero and any number of clicks used, although, more clicks are better for a good average.

 

[remingtonman_25_06]

Alright guys, heres a quick update. I think I know whats wrong now /ubbthreads/images/graemlins/mad.gif First things first was to zero at 100, I was zeroed at 200, so I just went 5 clicks low and shot at 100. I was still a tad high, moved down 2 clicks, shot was zeroed at 100 yards. Crony was reading a slow 3215fps average today /ubbthreads/images/graemlins/confused.gif I took the advice and dialed 20 MOA or 80 clicks up and shot 2 times to see where I was hitting at 100 yards. I was right at 20 1/4" high, so obviously my scope is not the problem here..The next thing I did was check my drops as recomended. Zeroed at 100, should put me 20" low at 400. Well I shot 3 shot group and to my surprise was 1.5" /ubbthreads/images/graemlins/grin.gif but was -23". So me thinking my Cronygraph is off here. I plugged everything in, if my bullets BC is around .485, then based on my drops at 400, I'm only running around 3075fps instead of 3250fps. 3075fps matches up a lot better at 400 and 800, according to what my clicks and load are doing anyways. I think I need a new cronograph, what do you all think???

 

[Michael Eichele]

Do you know anybody close to where you are to barrow one before you buy??

 

[davewilson]

i've never cared what the speed was or BC. just shoot it and see how many clicks it takes your scope to make it hit where you want.that's very reliable.

 

[dakor]

Rem I was not trying to be a jerk I was just stating that a 7mm Rm is not going to get that kinda velocity. If you have a 30inch pipe maybe. I have the Nosler book also and I would really like Nosler show me in person they are getting 3300fps with a 140 and the rifle is still in one piece. /ubbthreads/images/graemlins/smile.gif They are dreaming that is as fast as a STW will shoot and that is not going to happen. That is why I dumped the 7 RM and got a STW. I have the same chrony you do I also have two others. I can tell you that your graph is probably lying to you. I have had mine give me a reading one day and then the very next day with about the same conditions out give me a reading up to 100fps + or -. I have noticed it really does not seem to work well after the summer months I think it has to do with the sun not being as bright. I do not know what you are shooting for a rig but if you have a factory rifle with a 26inch pipe and can get more then 3150fps without pressure signs I would hold on to it. That is why when I was shooting any of the 5 7mm mags I had I went with 160gr bullets because I could shoot them around 3000fps and was only getting around 3100fps with 140's. Really does not make sense but that is how it worked out. One of them even had a Hart 27inch tube. If you do not like the 140 shooting that speed try a 160gr or more.

 

[remingtonman_25_06]

I dont know anyone with a cronograph around here, seems I'm the only one who thinks ya need one /ubbthreads/images/graemlins/smile.gif I dont know, I'm kinda dissappointed. I really like the 140g BT, it shoots great, just wished I knew what the real deal was. I'm still betting its the cronograph. So whats a decent cronograph that wont cost me an arm and a leg??

Dave- I agree to an extent. Theres no other sure way to know what your bullets are doing until you shoot them, but it would take forever to drop test and confirm zero'es every 25 yards, etc. Just seems like it woudl be tedious (sp?) work. I get frustrated to easily, might be part of my problem..