Well I searched here and didn't find anything.
Where are you guys with 20moa bases measuring for height for ballistic data? Granted I think it's only about a 0.10" difference from one end to the other but I am trying to get this nailed down pretty close.
Thanks!
its not a perfect world.
i usually measure from the gas port to the center of the scope ring.
daily fluctuations in temp. will affect your data. leaving ammo in a vehicle overnight when it goes
down to zero will affect your data. shot angle will affect your data. not to mention wind and thermal affect.
then all those unseen tree branches.
I know it's not a perfect world but the scope height is a variable I can remove. I use powder that is fairly temp insensitive, and when I go shoot I put the current environmental conditions in.
The thing is with a 20moa base the scope is physically not level with the barrel, at what point on the scope are the measurements needed to minimize calculation errors due to a measurement error.
Centerline of the windage knob to the centerline of the action.
Thanks!!Originally Posted by stangfish
I estimated this measurement, but after reading this post I think i will check it out. My data seemed to work well, but could be better for the 700yds+ area. That's where I started having more difficulty putting lead on target consistantly.
Well I put in the ballistics calculator for 1.25" and 1.50" scope height and at 1000 there is a 2.2" path deviation at 1000 yards so there it is almost 0.25 MOA at that point just in the difference of 0.25" of mounting hieght. This is where I was wanting to find the correct place to measure at so as were running to further distances to ensure my ballistics calculator is on par with what I am encountering at the range.
most often charts need tweeking before a final version. first off chronagraph information is rarly
perfectly accurate. id be printing a chart and go shoot. the actual shooting results trump all other
factors at least on that day under those conditions. you will no doubt be tweeking numbers in order
to match what you actually did. that will give you a baseline to go by. your weather station can be helpfull
in updating your data on subsequent outings. another option and the one i use is sighter shots.
today there is alot of talk about first round cold bore hits even at extreme distances. no doubt in some areas
that would be more important than in others due to terrain. we shoot across wide valleys onto steep mountainsides.
sorta like shooting at a picture on a wall. misses can be quickly evaluated corrections made and follow up shots
on their way in seconds. im well aware not all areas are as easy as that. a miss may in fact be hard to detect as to why.
thats where a buddy acting as a spotter is very important.
there is a 2.2" path deviation at 1000 yards
Think about it!!! 10 fps?
10fps is about 3.4" with the 175g SMK
I really want to try some 155SMK Palma bullets same BC but lighter and I can make them go faster!
The Bergers ar not that much more.
I never have had any good luck with Berger bullets they have always been temperamental with me.
data is simply a means of getting you on target quickly. seeing hits is far more important than data. even if you guess the yardage
and are wrong causing the shot to go 10' low. so long as you or your spotter saw it you can be on with the second shot or at least very close. my guess is you have an equiptment issue or your method needs to be scrutinized. are you shooting from your belly?
what cartridge are you using?
And which bergers. The heavier hybrids are a little more forgiving.
Yep shooting prone most of the time, like you said good data can get me there quicker and more reliable that's what I want it for.
This was off a bench the last time. And the wind had picked up in the afternoon. Also my brother in Law who was spotting is not trained to on what to look for as a spotter, so I had to try and do both to get on target. In SOCAL the ranges are usually in the hills, so there are multiple crosswinds to try and read. My data had me **** close, but there were a few items that I didn't have with me last time I went that I won't forget next time.
I was just excited to get the new build on the firing line. I'm sure there are some tweaks I could definitely make to my range card.
Yeah I'm from so Cal I know what you mean about battling the winds in the canyons and hills.
the wind isnt unique to ca. or any other part of this country it happens all over.
its simply something you learn to deal with that charts wont give you.
the questions about what cartridge and type of berger bullet havent been answered.
If wind is a big concern switch to a 6.5 of some sort. Much more forgiving in the wind.
It's not that big of a deal, I would like a 260 but it's not going to happen anytime soon
Well put yobuck. Understanding this in the big picture will gain the best results...
.22LR * 6.5x47 Lapua * .223 Rem * .308 Win * 260 Rem * Large Cojones!
[I]"I can prove anything by statistics except the truth."[/I]
Ok, now that we are back on target:I agree with JHelmuth that Yobuck's quotes get the big picture.
I would either go with Stangfish's statement, or would guess that the center of the reticle when properly focused and aligned with the target might be the answer, but I have no facts to back up my guess.
I realize this is still an approximation, and that's the best I believe we are going to get.
Think about the following:
Even if you have your scope mounted on a 0 MOA base, the angle (from horizontal) of the light path from the target through the center of the reticle to your eye is at the same angle as if the scope were mounted on a 20 MOA base.
So, the rhetorical questions I would ask are:
1. Is it really the height of the scope above the barrel that is important or is it really the height of the actual light path above the barrel that we should be measuring?
2. If the answer is the light path, then where along that light path do we measure "scope height?
This is a good academic question and discussion, but, at least for me, at some point I accept approximation as "good enough." I don't think I can consistently and deliberately change my POI by .25 MOA, so I have no problem accepting a reasonable "area of probability" in which my bullets will impact the target.
that sums up the whole discussion. we should attemt to use as accurate data as possible. but we also need to accept that data alone
wont improve what we lack in ability and or equiptment. this stuff can be learned very easily by average shooters who are willing
to listen.
im sure youd agree that their are 6.5s and then their are 6.5s. the wind will be more forgiving on the one driving a 140
@3300 than it will be on one @2800.
so now what happens if we drive a 284 180 berger at 3200?
or a 300 gr berger in a 338 @3200?
their all gonna be door to door to a point, after which the bigger bullet will prevail.
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