Tanks guns and ammunition.

[Mighty_Zuk]

2 hours ago, LoooSeR said:

Zvezda says that this is "secret" shell, so possibly they showed "Telnik" programmable HE-Frag.

   It is kind of... not very good. Amount of frag damage at such distance is rather low, IMO.

All I see is 3 minutes of a redcoat playing with a nice stick.

[LoooSeR]

43 minutes ago, Mighty_Zuk said:

All I see is 3 minutes of a redcoat playing with a nice stick.

15 hits in total for whole shield (which is wider than a human) which was around ~10 meters from detonation point.

[Mighty_Zuk]

43 minutes ago, LoooSeR said:

15 hits in total for whole shield (which is wider than a human) which was around ~10 meters from detonation point.

Which is what you could expect.... from a 40mm AB munition. 

[LoooSeR]

8 hours ago, Mighty_Zuk said:

Which is what you could expect.... from a 40mm AB munition. 

   Soldier inside of some sort dug in position and with body armor/helmet could have survived this explosion 10 meters away withouth much of problems. Thats why i think Zvezda is not saying thruth about shell being "secret". It is probably old He-frag that was made back in Soviet times for just developed Ainet system for T-80UK (APFSDS that they used in video was Mango, for example). I posted some time ago a pic of newer HE-frag (3OF82 projectile, part of 3VOF128 shot) with ready-to-use fragments, it should be noticeably better. 

 

[LoooSeR]

Ainet controls

[Mighty_Zuk]

1 hour ago, LoooSeR said:

   Soldier inside of some sort dug in position and with body armor/helmet could have survived this explosion 10 meters away withouth much of problems. Thats why i think Zvezda is not saying thruth about shell being "secret". It is probably old He-frag that was made back in Soviet times for just developed Ainet system for T-80UK (APFSDS that they used in video was Mango, for example). I posted some time ago a pic of newer HE-frag (3OF82 projectile, part of 3VOF128 shot) with ready-to-use fragments, it should be noticeably better. 

 

It doesn't look like it would be really noticeably better. 

I counted 12 rows per side with 7 fragments per row. 2 sides means 24 rows. Some are blocked from view so round it up to 30.

That's 210 fragments going forward. At least half of them will go upwards and above the target, and a considerable amount will go to both sides. 15 hits on a 2-man sized target simulating crouched men, sounds like it's statistically lower than what a 210-frag round would achieve, but not by far. 

 

Is there any "desirable effect" graph showing the distribution of an ideal/semi-realistic HE-F round over an area? Because the more I talk about it the more I realize I have no idea what am army would consider appropriate these days (though the tech hasn't changed much).

[LoooSeR]

 

Kind of related - 2E58 stabilizer for main gun.

 

Spoiler

   AFAIK this thing was planned to be part of upgrade for older tanks.

[Vicious_CB]

On 2/23/2019 at 1:04 AM, LoooSeR said:

   Soldier inside of some sort dug in position and with body armor/helmet could have survived this explosion 10 meters away withouth much of problems. Thats why i think Zvezda is not saying thruth about shell being "secret". It is probably old He-frag that was made back in Soviet times for just developed Ainet system for T-80UK (APFSDS that they used in video was Mango, for example). I posted some time ago a pic of newer HE-frag (3OF82 projectile, part of 3VOF128 shot) with ready-to-use fragments, it should be noticeably better. 

 

 

Looks like a nose fused round. I take it doesnt have a delay function to detonate after passing through walls and such?

[LoooSeR]

2 hours ago, Vicious_CB said:

 

Looks like a nose fused round. I take it doesnt have a delay function to detonate after passing through walls and such?

Yes, it is airburst only.

[FORMATOSE]

Regarding the length of the L29A1 C3TR :

 

 

Source : Service Inquiry CHALLENGER 2 Incident at Castlemartin Ranges, Pembrokeshire 14 Jun 17

[Wiedzmin]

and it's longer than L27 IIRC

 

 

[Lord_James]

Question for the more ballistically knowledgeable members of the forum (@Bronezhilet, @Collimatrix, @Sturgeon):

 

I'm designing a 6 inch (actually 155mm) (S)AP shell for a Destroyer Leader I am amateurishly designing (~160m long, ~14m beam, ~5m draft, 6000 metric tons standard), and need a little help. I have 2 main problems. 

 

• relating to Caliber Radius Head (crh), and it's component parts (mainly ballistic length and radius of curvature/caliber of ogive). I've made a rough outline in Inventor (with dimensions), and am a little confused about it's ballistic length: 

Spoiler

 

The purpose is to get the furthest range possible. The shell is 5.16crh long total with a 3/∞ crh windscreen. Target weight is ~55kg (~120lbs) and velocity is between 770-800m/s. Is meant to be used in a loader similar to that used in the Des Moines class cruisers. 

 

I have a conical ballistic cap that is 3crh long (465mm) and a boat tail (tracer element is also suppose to double as a base burn device), but I was going for an even longer ballistic cap length (I remember seeing a shell defined with a 6/12crh length, but I cant find that reference anymore) while keeping <800mm in total length and a high volume for more weight/ larger bursting charge. Should I increase the ballistic length even more, or change some other aspect of my shell? 

 

• Should I use a different shape? I read on Navweaps that US shells had a secant ogive, and this had better ballistics than tangent ogive, but they didn't compare it to conical. Is a conical windscreen the best choice for this shell? 

 

Other tips on how to improve this shell are also welcome (yes, I know I forgot my bourrelet and driving bands), but I'm most concerned with the windscreen/ballistic cap. Thank you in advance, 

 

Lord James 

[LostCosmonaut]

A von Karman ogive will give you the minimum drag for a fixed length and diameter.

 

They are significantly more of a pain to model in solidworks or similar software, for the tank design contest I just modeled my shells as tangent ogives, which I figured were close enough and much easier to draw.

[Sturgeon]

Here is a 5.69 caliber 5g 5.56mm small arms projectile with a Von Karman ogive:

 

 

It is tricky to do this in SolidWorks, but very possible. All of my current designs use VKOs, so once you get used to them they're not that big of a deal. I'd definitely say it's more of a pain in the ass to do the cannelure, actually.
 

As a shortcut, you can use a tangent ogive, or even better, a secant ogive. Secant ogives can even more closely approximate the VKO shape, without the hassle.

Also, your boattail is ogival. As counter-intuitive as it may seem, it's been proven for decades that conical boattails, not ogival ones, give the best drag and stability characteristics. Here's one supporting source. I think if you look at the overall shape of the projectile, you find that the conical boattail conforms better to the Sears-Haack/Von Karman shape than does an ogival boattail - this is because by necessity a bore-riding projectile needs to have a straight shank, you can't just make it a truncated S-H body, so the ogival portion is set further back. Another thing to note is that your boattail is probably shorter than you want - it's a little less than 0.65 calibers. The boattail in the small arms projectile above is 1 caliber long; conceivably it could be even longer. Longer boattails are harder to stabilize requiring tighter twist rates, but to be honest at the scale of a naval gun this is not likely a serious design constraint. I would use a boattail length of at least 0.8 calibers, and probably 1.0 or longer.

[Lord_James]

Ok, so what I’m getting is: 

 

• I need a near-conical, secant type windscreen, maybe something around 3/12crh. 
• Lengthen my boattail to ~1 caliber, and change it to a conical type with a gentle angle of around 8 degrees. 

 

I’m thinking about either a 3/12crh windscreen with a 1.0 cal conical boattail (which will give me 155mm to place the driving bands), or a 3.2/15crh windscreen with a 1.2 cal conical tail (I will have only ~80mm for driving bands), or some combination of those features. I’ll get on that tomorrow morning. Thanks for the help! 

[Sturgeon]

4 hours ago, Lord_James said:

I need a near-conical, secant type windscreen, maybe something around 3/12crh.

 

You want your secant ogive to have a radius that is about 7 times the full length of the ogive along the projectile. Like so:

 

This is the Army Ballistics Research Laboratory's AR-2 Short projectile shape. Note that even though there is a meplat at the tip I have extended the ogive to give the full length until it hits the y axis. The radius is 136.81mm, which divided by 19.56mm gives you almost exactly 7. Here's a closeup of the ogive, with a proportional Von Karman ogive overlayed on top for comparison (highlighted in baby blue):

 

You can see that this ratio gives you an ogive that is about as close as you can get to a VKO without going through the effort. This ratio changes a bit depending on the exact ogive length, but fortunately the AR-2 Short shape has an ogive length after meplat of 3.08, which is right around what you want.

[Lord_James]

New 155 modified design: 

 

Spoiler

 

Ballistic cap is now a 3.2/22.6crh (actually 3.226/22.58) secant ogive and the tail is a 1.2 cal, 8^o ,conical boattail. Radius of the secant is 3510mm (3508.9). 

 

As for the bourrelet and driving bands: 

• The bourrelet is flush with the end of the windscreen, and I think it's a little small but I know little about projectile design. 
• I have a bit of space to place a driving band on the shank, but while looking through some modern projectiles and how they are shaped, I found a HE shell with a sabot-like piece over its tail, which also contained the driving bands. If this is a reliable way to solve that problem, I could probably increase the length of the cap and/or tail. Conversely, I could also place a sabot-like piece over the cap that mounts the bourrelet, and I can place my driving bands on the shank; either seems acceptable (if they work as theorized). 

 

I also have a question about the meplat now: 

 

8 hours ago, Sturgeon said:

 

 

I see a lot of flat meplats at the end of large caliber (and rifle caliber, too) projectiles, but in your sketch here, it looks a little rounded, or at least angled (both the secant and VKO). Would a smaller or rounded/angled meplat have better ballistic properties, or is it like the boattail where it is counter-intuitive (until a certain point)? 

 

Either way, thank you for the advice! If there's anything that needs changing (or rather, more optimization) for the shell, I'm all ears. 

[Sturgeon]

35 minutes ago, Lord_James said:

I see a lot of flat meplats at the end of large caliber (and rifle caliber, too) projectiles, but in your sketch here, it looks a little rounded, or at least angled (both the secant and VKO). Would a smaller or rounded/angled meplat have better ballistic properties, or is it like the boattail where it is counter-intuitive (until a certain point)? 

 

Either way, thank you for the advice! If there's anything that needs changing (or rather, more optimization) for the shell, I'm all ears. 

 

The meplat on the VKO is rounded because that's what I had available (it comes from a bullet with a lathe-turned steel tip). The flatter meplat of the secant ogive AR-2 Short is a byproduct of manufacturing; it's difficult to draw brass that finely to a point (although they somehow did it with the original AR-2 Short projectiles, they are very fine). In my experiments with different meplat shapes, rounded is better. Given the scale of ammunition you are working with and the fact that you have an attached windscreen, I'd figure out just how fine you can make the meplat (probably very, very fine) and then use a circle tangent to the ogive and centered on the centerline.

[Lord_James]

I present the 155mm S12a APCBC-HE: 

 

 

46.1kg all together, with an aluminum outer shell, steel cap and body, and Explosive D burster (driving band 'sabot', tracer/burner, and base fuse not created yet). 

 

From left to right:

• Aluminum shell front (ballistic cap) ~0.8kg 
• Normalizing cap ~10.8kg 
• Projectile body ~31kg 
• Aluminum shell rear (cup) ~0.6kg 
• 2.87kg of Explosive D 

I probably fucked up the normalizing cap, so if anyone wants to elaborate, I would be grateful. 

[Lord_James]

On 2/4/2019 at 3:08 PM, Bronezhilet said:

Shape stabilisation increases drag though, and increasing drag together with lowering mass is a double whammy for your deceleration numbers. Although I haven't checked if the increase in Mv offsets the increase in drag.

 

Question: 

 

I remember, either you or someone else, said that soviet HEAT shells were primarily shape stabilized. Why are they referred to as HEAT-FS, and not HEAT-ShS (Shape Stabilized)? Also, do the fins do much of anything for those HEAT shells? 

 

Glad to hear you’re safe, and thank you in advance for the answer. 

[Ramlaen]

 

Quote

THE M865A1 CARTRIDGE IS 4 INCHES LONGER THAN THE CURRENT M865, TO MORE ACCURATELY REPLICATE THE LENGTH, WEIGHT, AND CENTER OF THE CURRENT TACTICAL CARTRIDGE (M829A4) IN ORDER TO IMPROVE TRAINING.

 

[Zadlo]

del

[Zadlo]

19 hours ago, Ramlaen said:

 

 

 

IMHO M829A4 can be thicker in diameter than M829A3 by around 2 milimeters. 

 

@Lord_James, I've recently read an article from early 90s about projecting 122mm round with enhanced range. 

And I'll give a small but important tip - use a hollow bottom in a round. In case of 122mm round it enhanced round's range for about 10 - 15%.

[Lord_James]

Finished 155mm S12a APHE naval shell: 

 

 

Spoiler

 

 

Top row (non-penetrating material) from left to right: 

• 3.2/22.6crh aluminum Ballistic Cap - 0.8kg
• 1.2cal boattailed aluminum Body (cup) - 0.67kg 
• Discarding rotating bands (aluminum and brass) - 0.44kg each (1.32kg total) 

 

Bottom row (penetration material) from left to right: 

• Hardened steel Cap - 11kg 
• Steel penetrator - 30.7kg 
• Explosive D Bursting Charge - 2.87kg 
• Base fuse (non self destroying) - 0.17kg 
• Tracer and Base Burner - 0.09kg 

 

Total mass: 47.8kg 

Ballistic mass: 46.48kg - 46.39kg (the lower number is for when the tracer burns out) 

Penetrating mass: 44.74kg 

 

I have no velocity for this round yet, as I have yet to make propellant charges and an actual gun, but I am planning on around 780m/s at muzzle. With these numbers, the penetration would come out to be 492mm point blank, but I doubt the DDL this goes with will fire at other ships PB. This might be better as a SAP shell as the late war 6"/47 heavy AP were 59kg, and travelling at a similar velocity. 

 

Anyway, I am always open to adjustments to the design, and I will not bore everyone here with more posts about Naval AP shells. 

[Ramlaen]