It is possible that a bump will knock a rifle heard enough to change zero. My experience is when it happens in not general by a inch. It's why you always check zero. I hunted Alaska , Africa, Argentina . I seen how badly they treat gun cases. I never have had a rifle lose it's base zero . I provide documentation for the shift of poi from what is considered the go to source for police and military snipers. I provide photographic evidence that I can build a accurate rifle , set it up and get it on target at 1100 plus yards with 15 rounds , true the data then on the next trip make spot on first round hits a 400, 900, and 1120. All we hear from you "It can t be and you don t know **** "
Different State - POI Change....is this normal?
- Thread starter Ingwe
- Start date
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Laws of physics.....i am not....
But....with Laws of physics a rain droplet is falling to the earth's surface...
Therefore a rain droplet would have less impact on bullet travel while it is below the path of the bullet..a droplet above would have more while above the bullet while in flight....therefore(and my assumption) wouldn't the bullet be more likely to be PUSHED downward when hitting the resistance of rain from above vs the rain that has already passed the bullets true poa flight path.....
I know a buddy had bullets blowing up from his 22250 in a drizzle....and when the sky cleared the next crow in the tree did also......
If you search for it there is high speed footage of bullets in flight. You can see the air being moved out of the bullets way. It leaves a wake just like a boat does. It's that wake that clears the path of the bullet that wake has more energy than the droplets. I shot in a drizzle many times and only difference I noticed was how easy it was to read wind. For the rain to have a impact it's mass and speed would have to equal or exceed that of the bullet
I only read but a few pages of this thread and seen a lot of guys speculating temp, baro/altitude, humidity, etc can change poi by 1 moa @ 100 yards. I do not think this is possible at that range. I went into my Ballistics AE app and, with a 0 yard zero (straight out the muzzle) and zero sight height, changed the conditions pretty severely and you probably cannot get 1/10" poi change of drop at that distance (more like 1/100"), let alone 1". If you think that a 20 or so feet per second change in velocity will change the poi by 1" @ 100 yards then we long range shooters have been kidding ourselves all these years, there is no way my rifle should be shooting under 2" groups at 800 yards unless the velocity spread is practically zero.
In Feb we were shooting our .300 WinMags out to 1200. Shot right before lunch and then it came a decent rain our second go around after. That was the only change in conditions and there was no noticeable change in poi using same dope.
The biggest factor to all the physics here......when the bullet leaves the barrel it is supposedly already slowing down.....true or not true....
Maybe the op was wearing gloves because he wasn't used to the climate..and that made him shoot differently.....
Op said he was busting PD's next day....but those are usually bigger than a dot on a target......
Maybe the op was wearing gloves because he wasn't used to the climate..and that made him shoot differently.....
Op said he was busting PD's next day....but those are usually bigger than a dot on a target......
It's a old school rule dealing with bullet profiles similar to 175 gr .308 match kings. The 20 degree change result in a change of air density. I can t get a ballistic program to mimic it either since I don t have a clue what to change air density to. The higher the bc of the bullet the less the effect since the eld profiles are by design resist drag. Look back to the post showing the formula from the police sniper manual. I have seen it on the range to a greater or lesser degree
HiTechRob
Active Member
Well, depending on the powder you are using, you can see a 1.5 fps to 3.5 fps variance in muzzle velocity in the same direction as your temperature change from zero. I see very little change using the Hodgdon Extreme powders like H1000 and Retumbo. For example, if the temperature went from 80F to 40F, then 40 x 1.5 = 60 fps decrease in MV up to 40 x 3.5 = 140 fps. That definitely will create a bullet impact change on the target and explains that you were low.... 1 inch low seems a bit much though. Also, a 2,100-foot increase in altitude, assuming pressure and humidity are constant, would negate that drop somewhat as the less dense the air is the less drag on the bullet and thus less drop you would have. What direction (N, S, E, W) you zeroed the rifle vs. the direction you shot can make a difference - but not at 100 yards... I shoot a 7RM as well but mainly shoot a 168-grain Berger VLD-H. It doesn't move much and my ballistic calculator is hooked up to my Kestrel wind meter to account for the change in zero environmentals vs. my current environmentals in my hunt area.
I hope that Ingwe will report back after his return home and trip to the range. Assuming he has the same Ammo. It doesn't sound like he dialed in a change, but if he did he could reset to original zero. If the rifle shoots to poa, we know the rifle is solid and the change was environmental.
The rule of 1 moa /20 degrees delt with expected shift due to air density and powder performance. So it adjusted for internal and external ballistic .
Nowoolies
Well-Known Member
Wow you really like your opinion hay
This thread is NOT about you your rifles or your loads
This thread is NOT about you your rifles or your loads
JDD,
I am at that point to where most of my students and peers would start to consider me old school and I am familiar with what those old school manuals say, having been a Military Sniper since before the proliferation of hand held ballistic calculators and now being a schoolhouse Senior Sniper Instructor. The problem with what you are pointing out is it's a generic solution instead of being specific, that and it doesn't effect trajectory at 100 yards.
As stated by another, even a big swing in velocity due to propellant temp will not account for such a change. Add that to a huge change in environmentals and you may not even get half of what the OP experienced. I suspect something far more nefarious.
I am at that point to where most of my students and peers would start to consider me old school and I am familiar with what those old school manuals say, having been a Military Sniper since before the proliferation of hand held ballistic calculators and now being a schoolhouse Senior Sniper Instructor. The problem with what you are pointing out is it's a generic solution instead of being specific, that and it doesn't effect trajectory at 100 yards.
As stated by another, even a big swing in velocity due to propellant temp will not account for such a change. Add that to a huge change in environmentals and you may not even get half of what the OP experienced. I suspect something far more nefarious.
JDD,
I am at that point to where most of my students and peers would start to consider me old school and I am familiar with what those old school manuals say, having been a Military Sniper since before the proliferation of hand held ballistic calculators and now being a schoolhouse Senior Sniper Instructor. The problem with what you are pointing out is it's a generic solution instead of being specific, that and it doesn't effect trajectory at 100 yards.
As stated by another, even a big swing in velocity due to propellant temp will not account for such a change. Add that to a huge change in environmentals and you may not even get half of what the OP experienced. I suspect something far more nefarious.
Thankfully another old school shooter who does t need a cell phone to connect. As you know every rifle and load is a story of its own. We seen a world of advancements in ballistics, bullet profile BC we never could imagine 20 years ago. The old formula accounted for a 2 moa change for temp and air density add back in 1 moa for the competing conditions of attitude . It explains the shift. THE ONLY WAY TO DETERMINE IF IT WAS ENVIRONMENTALS IS TO CHECK ZERO AT HOME RANGE . I Not yelling just typing for notice. If rifle returns to base zero it was environmental, if not could be gear failing to hold up. Depending on barrel profile a change in internal ballistic due to temperature could result in a difference in barrel time and a shift in poi. I just spent two years as a rso and volunteer instructor at a local 1200 yard range. I lost count how many rifles I help set and take out all the way to 1000 yards. Quality gear makes it easier, the electronics make it much easier and requires less math. I gotten spoiled
Nowoolies
Well-Known Member
strewth pal drop it will ya !!!
you are so full of s*^%
you are so full of s*^%
