Powders for 308
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great then now you know that a small headwind does more than cause a tiny drop in bullet impact. Headwinds and tailwinds are rarely if ever direct they will always shift back and forth. In the link they use a 10 mph wind shifting a measly 3° and it caused a 2 MOA shift. In F class terms that would move you from the X ring to the 8 ring.
Sine of 3 degrees is .05233.
A 10 mph wind from 3 degrees either direction of LOS will move shots horizontally a bit over half an inch if the drift rate is 10 inches (1 MOA) per mph at 1000 yards.
https://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
A 10 mph wind from 3 degrees either direction of LOS will move shots horizontally a bit over half an inch if the drift rate is 10 inches (1 MOA) per mph at 1000 yards.
https://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
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This is a good day out to 200 yards.
The flags are placed at 25 yard intervals. A constant wind is often non-existent and it's not unusual to have a variable wind out of one direction 25 yards down range from the line of fire and a totally different direction and velocity 175 yards down range and this says nothing for the 500 yard line. On a breezy day it's the shooter who can gauge the wind all the way downrange that takes the match. To believe the wind is a constant is just plain foolish. All the formulas are about useless for a changing wind.
The above was actually a shooters dream but even with the breeze out of one direction The velocity changes all the way out to 200 yards.
Ron
The flags are placed at 25 yard intervals. A constant wind is often non-existent and it's not unusual to have a variable wind out of one direction 25 yards down range from the line of fire and a totally different direction and velocity 175 yards down range and this says nothing for the 500 yard line. On a breezy day it's the shooter who can gauge the wind all the way downrange that takes the match. To believe the wind is a constant is just plain foolish. All the formulas are about useless for a changing wind.
The above was actually a shooters dream but even with the breeze out of one direction The velocity changes all the way out to 200 yards.
Ron
don't take this the wrong way Bart but I trust Damon Cali more than I trust you on this, once gain read the link. I have recently observed this phenomena myself, Damon is not making this up
https://bisonballistics.com/articles/why-headwinds-are-more-difficult-than-crosswinds
@ reloadron. yep when all the flags are blowing in one direction it is indeed a good thing, due to a 35 ft berm on the right and a 50 ft tree line on the left my range gets a swirling effect
back to topic this morning I tested out BLC-2 in my new .308 bolt build. I was shooting 45.0 gns topped with a 168 gn Nosler CC. I had loaded these for my AR10 a while back, charges were thrown not weighed, Remington 9 1/2 primers, LC mixed year cases. The barrel is 24 inches and fluted and it was pulled from a Savage 10 FP10 several years back and has appx 500 rounds down it. Once I had the scope dialed in I was hitting a 1 MOA plate consistently shooting prone from a bipod and bunny ear bag @ 200. Recoil seemed mild and I had no problem remaining on target through recoil but I had a muzzle brake on it.
https://bisonballistics.com/articles/why-headwinds-are-more-difficult-than-crosswinds
@ reloadron. yep when all the flags are blowing in one direction it is indeed a good thing, due to a 35 ft berm on the right and a 50 ft tree line on the left my range gets a swirling effect
back to topic this morning I tested out BLC-2 in my new .308 bolt build. I was shooting 45.0 gns topped with a 168 gn Nosler CC. I had loaded these for my AR10 a while back, charges were thrown not weighed, Remington 9 1/2 primers, LC mixed year cases. The barrel is 24 inches and fluted and it was pulled from a Savage 10 FP10 several years back and has appx 500 rounds down it. Once I had the scope dialed in I was hitting a 1 MOA plate consistently shooting prone from a bipod and bunny ear bag @ 200. Recoil seemed mild and I had no problem remaining on target through recoil but I had a muzzle brake on it.
Powders for 308
Oh right, back on topic. My choice of powders for .308 Winchester varies depending on rifle. For my M1A and AR10 I really like powders like IMR4895, Hogdon4895, Accurate Arms2495 and while I am not fond of it Varget but nothing slower than Varget for any of my gas guns. That includes an M1 Garand I have chambered in 7mm-08 which could easily be a .308 Winchester.
With my bolt gun in .308 Winchester I like the VihtaVuori powders like N135 and N140, Varget, Alliant RL15 and a few others.
My best suggestion as to a .308 Winchester Powder is try several in your rifle with several bullet weights and types. Since I haven't hunted in years most of what I shoot are match bullets or common 150 grain FMJ bullets. Suggestions are fine but you need to find what works for you in your gun(s).
Ron
Oh right, back on topic. My choice of powders for .308 Winchester varies depending on rifle. For my M1A and AR10 I really like powders like IMR4895, Hogdon4895, Accurate Arms2495 and while I am not fond of it Varget but nothing slower than Varget for any of my gas guns. That includes an M1 Garand I have chambered in 7mm-08 which could easily be a .308 Winchester.
With my bolt gun in .308 Winchester I like the VihtaVuori powders like N135 and N140, Varget, Alliant RL15 and a few others.
My best suggestion as to a .308 Winchester Powder is try several in your rifle with several bullet weights and types. Since I haven't hunted in years most of what I shoot are match bullets or common 150 grain FMJ bullets. Suggestions are fine but you need to find what works for you in your gun(s).
Ron
The trick is matching the powder to the bullet weight. The heavier the bullet, the better it will play with slow powders. I like the 4064 range of powders, and Varget was originally designed by ADI (as AR2208) to compete with 4064. With the 175-ish-grain bullet weights, the 4064s and Varget do very well. If you are going to shoot 125s and 150s, you may well discover your gun is happier with N135 or, sometimes, even with 3031. All you can do is try it.
Regarding the wind debate, the fishtailing wind simulated in the article isn't shifting 3°. The article says the standard deviation of the fishtailing is 3°. So the total error span for twenty shots will average 11°. Hence the bigger error.
You can use Didion's old formula from 1858 as an approximation. The sine of 11° is 0.19 on my calculator times 5 mph is 0.954 mph, times 1.46666… gives 1.399 ft/s, times 12, gives 16.8 inches per second for the span of the shift in crosswind velocity component. It's more precise to do ±5.5°, but at these angles, the error is less than half a percent, so I took the shortcut. If the bullet leaves the muzzle at 2800 fps, the vacuum TOF flight would be 3000 ft / 2800 fps, or 1.07 seconds. If the bullet has the equivalent of a G1 BC of 0.5 all the way to 1000, then the TOF in an ICAO standard atmosphere is 1.598 s (from an exterior ballistics calculator I wrote; cheating, but the only other way is measurement and Didion would have had a stepped sequence of ballistic pendulum measurements for this). The difference will be 0.528 s. Multiply that times 16.8 inches per second, and you get 8.704 inches of total shift in the horizontal plane. My ballistics software puts it at 8.69 to 8.91 inches, depending on if it is a tailwind or a headwind, but Didion's estimate still does pretty well for its age.
Regarding the wind debate, the fishtailing wind simulated in the article isn't shifting 3°. The article says the standard deviation of the fishtailing is 3°. So the total error span for twenty shots will average 11°. Hence the bigger error.
You can use Didion's old formula from 1858 as an approximation. The sine of 11° is 0.19 on my calculator times 5 mph is 0.954 mph, times 1.46666… gives 1.399 ft/s, times 12, gives 16.8 inches per second for the span of the shift in crosswind velocity component. It's more precise to do ±5.5°, but at these angles, the error is less than half a percent, so I took the shortcut. If the bullet leaves the muzzle at 2800 fps, the vacuum TOF flight would be 3000 ft / 2800 fps, or 1.07 seconds. If the bullet has the equivalent of a G1 BC of 0.5 all the way to 1000, then the TOF in an ICAO standard atmosphere is 1.598 s (from an exterior ballistics calculator I wrote; cheating, but the only other way is measurement and Didion would have had a stepped sequence of ballistic pendulum measurements for this). The difference will be 0.528 s. Multiply that times 16.8 inches per second, and you get 8.704 inches of total shift in the horizontal plane. My ballistics software puts it at 8.69 to 8.91 inches, depending on if it is a tailwind or a headwind, but Didion's estimate still does pretty well for its age.
I don't think I would know what to do with a steady crosswind. All the ranges I shoot at reassemble bowling alleys, the wind is either a tail wind, head wind or is playing ping pong bouncing off the tree lines and berms. Maybe up in the plains states or out in the desert they get a steady crosswind but in the pine forests and swamps of the south there aint no such thing
The calculation is for a single 5 mph wind vector whose deflection spans the expected extreme range from one side of the target to the other for 20 shots, -5.5° to +5.5° off the bore axis. Mind you, those values are for the expected two most extreme shots out of the 20, while the others will all be in between. There's no break from watching flags or, with pulled targets, seeing where the spotters appear on the other targets to reveal the action of wind not present all the way back at the firing point.