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The Small Arms Thread, Part 8: 2018; ICSR to be replaced by US Army with interim 15mm Revolver Cannon.


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24 minutes ago, Sturgeon said:

This is 4.9 inches drop at 200m:

 

That's a 5.5" B8 bullseye target, similar in size to a human heart or vital zone in the head

This is representative of 6.5 Grendel 123gr ammo from a 20" barrel or 100gr Grendel from a 14.5" barrel

The bigger circle is the extreme spread (2.5" at 100 meters), the smaller circle is a representative mean radius (0.865" at 100 meters)

Now, this is a 50% pH at 200m target

 

And you need less than 2.7" drop at 200m to achieve that. M855A1 has 3" drop at 200m with a 100m zero.

 

Are they still going on about the 6.5G being the universal cartridge and all that? 

 

Ive always thought 6.5G had it ass backwards. I want flat trajectory at the distances I would typically be shooting at(300m and in) and don't mind more drop further out since past a certain point the difference between a 5 and 6 mil drop at 800m is moot point using the hashmarks on your reticle. IMO the design philosophy behind the 5.45 cartridge is just right.  

 

 

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Let's all take a trip back to the late 1970s and early 1980s.  This was the time of punk.  This was the time of despair.   Punk was all about minimalism; strip everything down to a few chords, wear

Stechkin's Abakan (TKB-0146). https://www.kalashnikov.ru/abakan-stechkina-avtomat-stechkina-tkb-0146/        Bullpup, system of "recoil impulse shifted in time", 2-stage

So what, my 5.56 rounds are groundbreaking too if I shoot the dirt.

1 minute ago, Vicious_CB said:

 

Are they still going on about the 6.5G being the universal cartridge and all that? 

 

Ive always thought 6.5G had it ass backwards. I want flat trajectory at the distances I would typically be shooting at(300m and in) and don't mind more drop further out since past a certain point the difference between a 5 and 6 mil drop at 800m is moot point using the hashmarks on your reticle. IMO the design philosophy behind the 5.45 cartridge is just right.  

 

 

 

You'd love the 5.7mm Hermes, then.

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On 10/22/2018 at 10:30 AM, Sturgeon said:

5.7mm Hermes would use 5.45 brass cases, blown out and necked (slightly) up for .224" caliber projectiles. Case capacity is 29.5 grs H2O. It's designed to propel a 57gr very low drag VKO bullet at 3,000 ft/s from a 14.5" barrel. 

 

I like it! Thats quite a long 57gr bullet, it should have some nice flight characteristics and good terminal ballistic potential. Some guys did a doppler radar regression of the 7n6 bullet and the results were quite surprising, it had a BC similar to a 77gr SMK, I need to check my notes to see exactly what is was but it was ahead of its time, basically 5.56 NATO 2.0 but made with shittier materials. 

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1 minute ago, Vicious_CB said:

 

I like it! Thats quite a long 57gr bullet, it should have some nice flight characteristics and good terminal ballistic potential. Some guys did a doppler radar regression of the 7n6 bullet and the results were quite surprising, it had a BC similar to a 77gr SMK, I need to check my notes to see exactly what is was but it was ahead of its time, basically 5.56 NATO 2.0 but made with shittier materials. 


IIRC ARL doppler testing of the 7N6 bullet showed an 0.168 G7 BC. For 7N22 it clocks an 0.180 G7.

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Not as high as I thought but still pretty good. Are you using the all "green" construction for the EPR bullet 57gr bullet? I wonder how much extra case capacity you can get by going with a regular lead filled base instead of copper. Or just do it like the russians with a full length penetrator.. 

 

5_457N54RAP_014_JPG-636932.jpg

 

5_457N54RAP_002_JPG-636930.jpg

5_457N54RAP_010_JPG-636931.jpg

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21 minutes ago, Vicious_CB said:

Not as high as I thought but still pretty good. Are you using the all "green" construction for the EPR bullet 57gr bullet? I wonder how much extra case capacity you can get by going with a regular lead filled base instead of copper. Or just do it like the russians with a full length penetrator.. 

 

5_457N54RAP_014_JPG-636932.jpg

 

5_457N54RAP_002_JPG-636930.jpg

5_457N54RAP_010_JPG-636931.jpg

 

I definitely recommend reading my articles on BC and form factor:

 

https://www.thefirearmblog.com/blog/2016/05/13/ballistics-101-ballistic-coefficient/

 

https://www.thefirearmblog.com/blog/2016/05/16/more-on-ballistic-coefficients/

 

https://www.thefirearmblog.com/blog/2016/06/09/ballistics-101-form-factor/

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2 minutes ago, Ramlaen said:

But it "wasn't designed" to do that. 

 

M193 frags but "not by design".

 

But it's a trite clause at best. We could say the main design is to punch a hole in paper. But if it just so happens to violently expand and induce polonium poisoning then that's totally not the main design. Totally an accident. Just a little fluke. Lolz we already made some so piss off.

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      There are many who feel that the 5.56 NATO is a superlative rifle round. Much has been said about larger alternatives to 5.56, such as various 6.5mm and 6.8mm rounds among others. Less has been said about smaller rounds. Off the top of my head, I can recall that there was a German 4.6x36mm round, used in the HK36, and the British 4.85x49mm round. Neither of these rounds managed to gain widespread acceptance. My knowledge of the voodoo that is ballistics is somewhat limited, so I'm uncertain as to whether these failures were caused by flaws with the rounds themselves, or because they were below some lower limit of effective bullet size, beyond which performance decreases rapidly. Could we see a resurgence of these concepts in the future, or do they represent an evolutionary dead-end?

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