Megawatt maker
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I have not bought a factory 300 RUM round in 15 years, and won't. They want way too much money for a lousy box of 20. I can load almost 60 (or more) for the same price.
Spin drift.
- Thread starter Megawatt maker
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Megawatt maker
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Maybe...but to each their own. Even zeroed at 300..it only shoots about 2 inches high at 100. Good enough for hunting and a lot of everything else. I just don't see the need myself. I'm not shooting in competition.
Varminterror
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There’s a disjunction between 1.5moa shift in 100-300 and .5moa shift 300-600.
There is no environmental or physical effect which would cause this. Even pointing at scope cant or crooked tracking doesn’t compute here. We gotta chase rabbits which will actually get us fed here - Corvette, Cowabunga, Welsh Corgi… however we misspell it, Coriolis and Eötvös isn’t the answer here… Magnus Effect, Spin Drift… Scope cant, adjustment lash… none of these are consistent with what you’re seeing, so chasing these rabbits ain’t gonna get you fed.
Lateral drifts are almost always dominated by wind - simply because it takes such little wind change to promote bigger lateral shifts than any of these minuscule other effects.
Maybe I can point it this way: I don’t make any corrections for Coriolis for any of my rifles at this range of 100, 300, or 600, and I never get that kind of shifting - regardless of zero, it’s not happening because of Coriolis. So don’t waste energy chasing that rabbit - certainly not any more energy than turning 90 or 180 degrees and showing yourself that it’s NOT Coriolis. I am damned certain the 1.5moa offset from 100-300 is not Coriolis related, as that shift is around 10x in magnitude greater than possible.
If it repeats in varying winds, then you eliminate the most common influence in lateral shift - wind. If it repeats with a different scope (confirming mount integrity along the way), you’ve eliminated the second and third most common influences in lateral shifts.
The groups pictured look to have a lot more horizontal dispersion than vertical, and 3 shot groups may not be telling the whole picture. Comparing loads with two different powders at 600 yards for 3 shot groups and making POA corrections, eh, that’s not common marksmanship strategy… kinda just throwing spaghetti at the wall and wondering why one piece stuck over here in an S shape and another piece stuck over there, shaped like a fish… do we think the two powders (are both charge weights optimized?) SHOULD have the same POI at 600? Especially when there’s only half inch or so between 2 shots each of the 2 groups on that page - despite a reported 3” left adjustment.
I can’t see a smoking gun here, but I can readily point away from the proposed issues of Coriolis, spin drift, and scope cant.
There is no environmental or physical effect which would cause this. Even pointing at scope cant or crooked tracking doesn’t compute here. We gotta chase rabbits which will actually get us fed here - Corvette, Cowabunga, Welsh Corgi… however we misspell it, Coriolis and Eötvös isn’t the answer here… Magnus Effect, Spin Drift… Scope cant, adjustment lash… none of these are consistent with what you’re seeing, so chasing these rabbits ain’t gonna get you fed.
Lateral drifts are almost always dominated by wind - simply because it takes such little wind change to promote bigger lateral shifts than any of these minuscule other effects.
Maybe I can point it this way: I don’t make any corrections for Coriolis for any of my rifles at this range of 100, 300, or 600, and I never get that kind of shifting - regardless of zero, it’s not happening because of Coriolis. So don’t waste energy chasing that rabbit - certainly not any more energy than turning 90 or 180 degrees and showing yourself that it’s NOT Coriolis. I am damned certain the 1.5moa offset from 100-300 is not Coriolis related, as that shift is around 10x in magnitude greater than possible.
If it repeats in varying winds, then you eliminate the most common influence in lateral shift - wind. If it repeats with a different scope (confirming mount integrity along the way), you’ve eliminated the second and third most common influences in lateral shifts.
The groups pictured look to have a lot more horizontal dispersion than vertical, and 3 shot groups may not be telling the whole picture. Comparing loads with two different powders at 600 yards for 3 shot groups and making POA corrections, eh, that’s not common marksmanship strategy… kinda just throwing spaghetti at the wall and wondering why one piece stuck over here in an S shape and another piece stuck over there, shaped like a fish… do we think the two powders (are both charge weights optimized?) SHOULD have the same POI at 600? Especially when there’s only half inch or so between 2 shots each of the 2 groups on that page - despite a reported 3” left adjustment.
I can’t see a smoking gun here, but I can readily point away from the proposed issues of Coriolis, spin drift, and scope cant.
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JFrank
Member
@Varminterror IMO is correct, thats not spin drift causing the variance on paper, double check your scope of course and finish the load development over a good set of wind flags.
C-grunt
Member
I agree that it's probably wind. A 300 RUM is a powerful cartridge but it's not going to take much wind to move those rounds a few inches at 600 yards.
Another option.... Try another proven scope on the rifle. Leupold makes good stuff. I love my Mk5. But it's still an mechanical object made by man and can be broken out of the box.
Another option.... Try another proven scope on the rifle. Leupold makes good stuff. I love my Mk5. But it's still an mechanical object made by man and can be broken out of the box.
JFrank
Member
Yes the scope may have a poi shift after the first round or adjustment and the settle and print groups, then again it might just not shoot well past 3000 fps.
I’ve attached some 300 saum AI load development from a friend whom is quite detailed and accomplished just for thought on foremat and a link to a scope discussion.
https://forum.accurateshooter.com/threads/tested-12-scopes-today.3964653/
I’ve attached some 300 saum AI load development from a friend whom is quite detailed and accomplished just for thought on foremat and a link to a scope discussion.
https://forum.accurateshooter.com/threads/tested-12-scopes-today.3964653/
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FL-NC
Member
Spin drift is usually not real.
FL-NC
Member
yesOh ?
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Varminterror
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Oh ?
.
Cruising at a very moderate pace, about as bad as it gets for the task, my Dasher load only has .2 spin drift at 1000. Sure, that’s 7.2”, but that’s also equivalent to only 1mph wind error…. At 600, spin drift is 0.1… one click difference from compensated to not…
Is it real, or is it REALLY real? Eh. I have spin drift compensation active in my ballistic solvers (I don’t activate Coriolis compensation for anything under a mile), and I correct my wind direction. But it’s pretty rare that I can estimate wind to +/-1mph down range, let alone better. My scores MIGHT change if I didn’t compensate for spin drift… MIGHT… but probably not…
GooseGestapo
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You grossly misunderstood and misrepresented what I actually wrote! But you were correct on the misspelling of coriolis. Spellcheck got me. Also left hand twist of 5R rifling.
So rest easy, I just deleted my post....
foxmeadow
Member
I disabled mine I've never meant to type "ducking"...
I have a VX5HD that has the reticle in the scope crooked.I could level by the turret top and when I double checked it with the plumb bob it showed up.It's on my to do list to get it sent off and fixed.I've found it best to level the rifle and use the bob to get the crosshairs right.Rifle cant starts to make quite a difference past 300 yards.Wind,terrain and mirage conditions are what I've found to be the hardest to work around by far more than spin drift or corpuscle effect.(not auto correct,just being a butthead)I learned the hard way how much rifle cant can come into play when I was shooting a 280AI I had just built at 1,000 yards on a calm morning.I wanted to get it shooting before the sun came up and the mirage and summer breeze got too bad and I was in too much of a hurry to put a level on it.Despite the fact that there was no wind to speak of I was getting a lot of horizontal,and the rifle had been well under half MOA when I was setting it up at 100 yards.I was shooting at a 16 inch plate at 1,025 yards to be exact,and I couldn't keep it on the plate,sometimes shooting left and sometimes shooting right with very little vertical change.I had a little level in my drag bag and I used it on top of the scope to get the rifle settled down.I just set it on top of the turret,leveled the rifle and shot.The level fell off under recoil and I had to fool with it each shot,but it took the horizontal out and the rifle shot like it should.
I shoot 600 yards at a different location than I shoot 1,000,and every rifle I shoot there shoots to the right a few inches,and I've never really figured that out.It's in a field that is at the foot of a steep ridge to the left of where I shoot and I don't know if it's air stacking up or something else that causes it,and that's why I mentioned terrain.I have to view shooting in a different light when I go beyond 300 yards.The guys who can set up,read the conditions and make a good shot right off the bat at long range have my respect and admiration.Even though I've put a lot of shots downrange beyond 300 yards,I'm seldom ever right on at anything beyond 500.I've done a lot of shooting with different rifles in the wind at 500 yards,and it can be tough.Up until this last component shortage I was shooting 500 yards on every windy Sunday afternoon that came along just to try and learn how to deal with it.I learned quite a bit,and one thing I found out is that no cartridge will shoot well in the wind if the shooter can't.Many things come into play as distance increases,and all of them can have a profound effect on where the bullet goes.
I shoot 600 yards at a different location than I shoot 1,000,and every rifle I shoot there shoots to the right a few inches,and I've never really figured that out.It's in a field that is at the foot of a steep ridge to the left of where I shoot and I don't know if it's air stacking up or something else that causes it,and that's why I mentioned terrain.I have to view shooting in a different light when I go beyond 300 yards.The guys who can set up,read the conditions and make a good shot right off the bat at long range have my respect and admiration.Even though I've put a lot of shots downrange beyond 300 yards,I'm seldom ever right on at anything beyond 500.I've done a lot of shooting with different rifles in the wind at 500 yards,and it can be tough.Up until this last component shortage I was shooting 500 yards on every windy Sunday afternoon that came along just to try and learn how to deal with it.I learned quite a bit,and one thing I found out is that no cartridge will shoot well in the wind if the shooter can't.Many things come into play as distance increases,and all of them can have a profound effect on where the bullet goes.
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