6 ms·
Two interesting observations from this article: * I am more amazed at the quality of the scope that the shooter could place a bullet on a 8" bullseye at a dist
by srvmshr 4y ago
Two interesting observations from this article:
* I am more amazed at the quality of the scope that the shooter could place a bullet on a 8" bullseye at a distance of 7.08km. There must be something fascinating to it since, Rayleigh's criterion for resolving two points puts some physical limits to the aperture. To resolve a palm sized mark, you need a sufficiently large aperture on telescope & that's not easy to mount/operate.
* This is one of the neatest images I have seen of the effect of rifling on the bullet, in addition to the thermochemical effect on the bullet tip. The tip at that distance & time of flight goes through sustained heating & there is some evidence of rapid oxidation - much like a piece of metal exposed for few seconds to blowtorch.
- twawaaay 4y agoI am pretty sure in this case the scope is used just like scopes on artillery. You would be interested how artillery scopes resolve from tens of kilometers? They do not.
- somat 4y agoartillery can rarely see their target. My understanding is they use a reference point they place near by and are good at turning offsets to this to the correct angle and powder charge to reach the target. it helps to have an observer that can see the target the can provide aim adjust feedback. Note that they can do direct fire missions where the target is sighted directly. but I think that is considered too damn close when that happens. Also note that tanks(a direct fire device) have been known to engage targets at 4+ kilometers. Probably a case of a large stable mount, and a good targeting computer. A fun fact, computing artillery tables was the primary task of some of the first electronic computers.
- wlesieutre 4y agoAnd before the electronic computers, we used mechanical computers! https://hackaday.com/2013/03/13/retrotechtacular-mechanical-targeting-computers/ https://hackaday.com/2013/03/13/retrotechtacular-mechanical-...
- iancmceachern 4y agoAnd before that we used human computers! https://en.m.wikipedia.org/wiki/Computer_(occupation) https://en.m.wikipedia.org/wiki/Computer_(occupation)
- adrian_b 4y agoThe first job that my father got (around 1953) was as a "computer", at an astronomical observatory. However, such jobs have started to disappear very quickly after that time, with the spread of the electronic computers.
- chrisseaton 4y agoAnd conversely we sometimes use direct fire weapons such as machine guns in an indirect fire mode.
- Alupis 4y agoThe article mentions it's a variable optic with 6-35x. 35 power is nothing at 4.4 miles... the target was probably smaller than the reticle crosshair. For reference, most of your typical spotting scopes are 60x... and even at 1,000 yards things are hard to see. Here's an article with helpful images through several popular spotting scopes for comparison[1]. [1] https://www.pewpewtactical.com/best-spotting-scopes/ https://www.pewpewtactical.com/best-spotting-scopes/
- kevin_thibedeau 4y agoThat looks like rusted iron residue transferred from the sheet metal backing of the target. They had a board down the middle that they had to cut away to extract the bullet so it was encased in the wood for a while with vaporized metal and water before they got it out.
- Alupis 4y agoI don't see where they tell us what bullet they used, but it's hinted at being a copper jacketed/bonded lead bullet. So we're seeing copper, and black residue from barrel fouling, aka. powder residue from inside the barrel's rifling. You should be able to wash and/or tumble most of the residue off the bullet and get something shiny out of it.
- leereeves 4y agoThe article said the bullet was: "The .416 Barrett cartridge is made by “necking down” a .50 Browning Machine Gun (BMG) round to accommodate the roughly .40-caliber bullet. It’s a relatively short, stout bullet that proved ideal for its purpose, Humphries said." and: "a 422-grain copper bullet"
- Alupis 4y agoThat doesn't tell us what bullet was used... that only tells us what caliber and weight was used. There are many bullet designs and materials. Additionally, the cartridge powder load will matter for ultra-long range shots like this too, so knowing what brand of powder, model and how many grains would be helpful too. A shot like this almost certainly used a hand-assembled, custom round. But the bullet itself is probably "off the shelf" and so would be the powder and case too. The exact combination might be their "secret sauce" though... long range folks get weird about this stuff.
- thereisnospork 4y ago>But the bullet itself is probably "off the shelf" and so would be the powder and case too. At this level I wouldn't be surprised if they did something ridiculous like CNC machine a copper billet bullet to ~micron tolerance/consistency. That said, from the pictures they appear to at least start with a commercial or 'to-spec' round from the company Unknown Munitions.
- Vexs 4y agoFor those curious, the specific scope is this one: https://vortexoptics.com/razor-hd-gen-iii-6-36x56.html https://vortexoptics.com/razor-hd-gen-iii-6-36x56.html
- alostpuppy 4y agoI really expected it to be more expensive.
- walrus01 4y agoAnything more expensive available for civilians is generally thermal or night vision, it's easy to spend $6k-8k on a scope with half the zoom but thermal 640x384 sensor capabilities. People use $4000-9000 thermal scopes at much less zoom and much shorter ranges under 400 yards shooting feral hogs in Texas.
- hajile 4y agoThey aren't quite at the top-end price of traditional scopes. Hensoldt makes scopes that go for almost $8k. They aren't aiming for a 4-6 inch target though (I seriously doubt you could even see that with 35x at 4.5 miles). They are aiming for the center of a target 7.5 feet by 10 feet. The difference between that 8k scope and this 4k scope is mostly a tiny bit of clarity and last 2-3% of fit and finish. Neither of these would affect scope accuracy and the clarity wouldn't exist at that range anyway due to particles in the air. No purpose in special ordering one and blowing 4k that could be spent elsewhere on something that won't impact the actual shot.
- Cd00d 4y agoWhat is that they have mounted on the front of the scope?
- dymk 4y agoLooks like a Charlie TARAC from the youtube comments - https://tacomhq.com/charlie-tarac/ https://tacomhq.com/charlie-tarac/
- nullc 4y agoRayleigh's criterion doesn't hard limit your ability to aim-- so long as you have a good prior what the image plane projection of the target is. To give a contrived example. Say we have a function f(x) == a*exp(-(x-m)^2). I evaluate f(x) at 1 and 2 and tell you that the evaluations are f(1)=0.27093242847450331643480903517 and f(2)=1.1666240719274935885932696286. From that, you can tell me the amplitude (a) and peak position (m) with on the order of 100 bits of precision (in this example). This is contrived because its noiseless and you know the system response perfectly, but I think it demonstrates that an alignment under assumptions need not be limited by rayleigh's criterion.
- tromp 4y agoFor this kind of experiment, do you even need a scope? (Asking as a complete noob). It seems what you need most of all, is the ability to make the most minute of adjustments to the aim of the rifle, combined with feedback on where the last bullet landed relative to the target. Then it becomes a bit like Newton-Raphson approximation. Or are the conditions on the record such that each successive firing must aim from scratch? One question of interest is how far repeated shots with the exact same rifle aim are going to land from each other. That would depend on changing wind directions and other atmospheric effects. Presumably you pick a day of near zero winds for such attempts.
- simonh 4y agoAgreed, the scope is really just a rough aid in an application like this. How do you even know how to adjust the scope for that range in the first place? You’d zero in on the target by adjusting group to group, or in this case probably shot to shot.