• If you were supposed to get an email from the forum but didn't (e.g. to verify your account for registration), email Wes at stararmy@gmail.com or talk to me on Discord for help. Sometimes the server hits our limit of emails we can send per hour.
  • Get in our Discord chat! Discord.gg/stararmy

Sivaro Automatic Assault Carbine

Status
Not open for further replies.
This feels a little off.

The slug is very, very light for its caliber. Unless the slug has a coefficient of something 1 or less -- low drag -- you'll never get to 200 max yards, much less 200 effective yards.

Imagine a .45 pistol round. Its velocity doesn't even rise above subsonic. However, it has a good BC because of its weight. Likewise, .223 has a good BC because it is a subcaliber bullet that is light but aerodynamic and with a lot of powder behind it.

Your bullet weight needs to be much heavier if it is to achieve the results you want out of a semi-auto carbine.
 
Projection/ammo type:.460 SVO
80 gr (5 g)3,050 ft/s (930 m/s)1,680 ft·lbf (2,280 J)
Click to expand...

and range is listed as
Maximum Range: 750 Meters
Click to expand...

A quick glance a google shows that 9mm rounds with about half that kinetic energy will go more than twice as far.

Of course the trade off between range, speed, and weight isn't geometric, but all things considered Edto's stats look conservative for range.


Edit:

Checked with a few calculators online, and it looks like with different drag co-efficients you can get wildly different answers. With higher values I'm still seeing the bullet get out to around 600m before stopping at worst. Using the above calculator with the average amount of Drag the bullet is still quite deadly out past 1000 yards..
 
Last edited:
The problem is bullet shape.

With the statistics he has listed, the bullet either is very wide at the base before sharply tapering into a hollowpoint, or it's very long and practically hollow.

.460 is a huge caliber for a rifle round. For instance, check out .460 Weatherby, then look at its ballistics.

https://en.wikipedia.org/wiki/.460_Weatherby_Magnum?wprov=sfla1

That is the bullet's shape with 500 grains to work with. It still gets its speed close to Edto's round.

Imagine taking that bullet and hollowing out more than 80 percent of its weight. That is a terrible design; it would capture wind like a net and bleed energy far too fast. 750 yards would not come accurately, if at all. See how .460 Weatherby holds its energy well and flies straight, but eventually hits the dirt at 250 yards? Depending on shape, your bullet would fall before that because it lacks weight.

See where I'm getting at? Modern bullets don't do what your bullet does. If I use .460 S&W for your bullet shape, your bullet flies very straight, but it loses almost 67 percent of its energy at 250 yards. It doesn't make it to 750 yards before it hits dirt.

Use a typical .460 Wea. Mag. for your bullet shape and you hold energy and distance better, but still not very well, and it won't shoot as flat. And it falls before 750 again. Make it a hollowpoint and your coefficient will get worse; air resistance will build faster and reduce energy and range.

That's why I say that your bullet is too light for its caliber and speed. You need a heavier bullet to make your round really work.
 
Caliber is the width of the bullet, the casing and the explosive bits don't really factor into it.

This is an SMG, not a rifle, so large rounds are to be expected but in order to head off the next few questions we're firing this so fast modern weapons aren't an apt comparison.

Assuming this round has the worst possible design, it still dangerous out to 750 meters (820 yards). In this scenario you're aiming upward at maybe a 45 degree angle and lobbing rounds at the target like you have a mortar but you're still going to kill someone on the opposing end.

View attachment 5979

More reasonably, you could have a disk shaped innard that breaks apart hollow point style and then have a thin ballistic cap built around the round. If you really wanted to super-science it you could apply all kinds of special coatings to the round, or have a small tail-bleed-thing in the round to improve drag qualities. So if we plug in the variables for 'having a ballistic co-efficient similar to very terrible rounds' we end up with something more like this:

View attachment 5980

Ok, not NEARLY so bad as the worst case scenario, but still pretty bad. at 750 meters (820 yards) you're still having to arc your bullets pretty heavily to hit the target but the round is still deadly well past 750m.

---

Maximum range is a bit of an abstract quality here, but I would certainly think 750 is reasonable.
 
Ah. .460 Rowland. Now we are talking.

Zack's table assumes the worst, but we can get much closer with a sister round to the .460 -- the .45 Win Mag.

If we take your load that you took from Wikipedia and apply it to a bullet that's similar, we get a chart that, at 200 yards, shows a loss of more than 50 percent of its energy, but it flies pretty darn straight. So you've got that!

But it also hits the ground between 400-500 yards. Getting to 750 isn't just arcing; you are shooting a true rainbow. That's not practical and should not be considered viable.

Now. Is this meant to be an SMG/pistol-round carbine, or is it firing an actual rifle round? .460 Rowland is a pistol round used for match shooting and close-range hunting. Close as in under 100 yards. If you want a pistol round fired out of a long gun, no problem. But it means cutting your range to something reasonable, and understanding that it won't be accurate much beyond 200 yards, far less with wind.
 
I really don't care about range honestly. within 100 yards is more than enough for underground combat

I'll make max 350
 
but we can get much closer with a sister round to the .460 -- the .45 Win Mag.
Click to expand...

Closer than the actual math for the hypothetical round? We can determine exactly how far the round drops over a distance and saying it hits the ground between400-500 yards is demonstratably false. Your comparisons are for a round with about half the kinetic energy, so you're way off in terms of your estimations. For hitting a target at ~ 800 yards you're only having to aim up a few degrees (~10 yards above the target if you're sight is dead on, or aiming up .7 degrees). Not exactly shooting the rainbow, since it only requires aiming up a few degrees.
 
The calculator I used lets me replace speed and weight while keeping bullet shape static. That's how I was able to do my calculations.

Thank you, Edto. Let me know when that change is ready. Do you plan to use this round in other weapons?
 
I'm wondering what calculator you used.

Ballistics calculators use a value called ballistics co-efficient rather than shape. Ballistics co-efficient is a combined value for shape, texture, ect calculated by how much velocity the bullet loses at a certain amount of distance from the muzzle. Not only is your estimation off from what I got, but if you used the ballistic coefficient for the .46 or .45 you should have gotten a result with better range as generally the larger the round the better the ballistic coefficient.
 
I don't think you understand guns as well as you'd like to make it sound. That's ok.

I used gundata's calc. Lets you modify BC separate of speed and grain. Bigger =/= better BC, if you'd check your math there.

I used shape as shorthand for BC because I changed bullets first, then changed the values so it would assume a certain shape before I calculated.
 
Doshii Jun said:
The calculator I used lets me replace speed and weight while keeping bullet shape static. That's how I was able to do my calculations.

Thank you, Edto. Let me know when that change is ready. Do you plan to use this round in other weapons?
Click to expand...
Yes I plan for other rounds to be used at a later date. I will be adding an Ammunition, upgrades, and attatchments section to this wiki.
 
Sweetness. Just submit rounds separately and we're gold. I got into the round before remembering that.
 
Doshii Jun said:
Sweetness. Just submit rounds separately and we're gold. I got into the round before remembering that.
Click to expand...
Why do I need to make a new Wiki for every ammunition type? It just adds to a bunch of smaller wiki's that could easily be dealt with on the main wiki without having to open up new tabs.
 
I can't duplicate your results using your calculator. The calculator you are using is giving me the same results I got earlier.

You also don't seem to understand what ballistic coifficent is, but that is ok. bc improves as size increases because you have more interior and less surface volume which means less drag per weight. Shape is only part of BC and due to the weight of the round, using the BC from .45 rounds is going to give you a very incorrect result. It also should make the rounds fly further.

I would love to see how you got your results on the calculator.
 
Edto Xar'Sivaree said:
Why do I need to make a new Wiki for every ammunition type? It just adds to a bunch of smaller wiki's that could easily be dealt with on the main wiki without having to open up new tabs.
Click to expand...
Not a new wiki, but a collected page of them. Those are the rules we set up, so that way each time a weapon using a round is created, the round can be linked to its place on that collected page. It cuts down on copypasta.

Zack, I'll respond after I get dinner. Hopefully W doesn't wake up; if he does, you can take my word for it on the results.
 
Last edited:
I believe I paraphrased your links earlier on. I was looking at these tables when I wrote about how a larger bullet leads to a better ballistic co-efficient.

You linked my supporting documentation.


Can you show me the values you used on the calculator to get to your conclusion? I think the only way you could have gotten close to your estimation is if you mistook grains for grams and put in 5 instead of 80.



---

Edit: Just to show you what I mean, here is the table from the first link that shows a better BC value for larger rounds, of course there is a lot of variation on that because of grain and propellant but it is generally trending upward as rounds get heavier/larger:



  • .224" (.22) 55 grain, BC .255
    .243" (6mm) 90 grain, BC .385
    .243" (6mm) 100 grain BT, BC .430
    .257" (.25) 100 grain BT, BC .393
    .257" (.25) 120 grain BT, BC .435
    .264" (6.5mm) 120 grain, BC .433
    .264" (6.5mm) 140 grain, BC .496
    .277" (.270) 130 grain BT, BC .449
    .284" (7mm) 145 grain, BC .457
    .308" (.30) 150 grain BT, BC .423
    .308" (.30) 165 grain BT, BC .477
    .311" (.303) 150 grain, BC .411
    .323" (8mm) 150 grain, BC .369
    .338" (.338) 200 grain, BC .448
    .375" (.375) 270 grain BT, BC .429
 
Last edited:
Status
Not open for further replies.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…