This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.
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What about muzzle report / recoil? Is there a worthwhile difference between 20 and 30?
The projectile does the work, and straight (or near) straight walled cartridges give you the most projectile for the volume taken up by the ammunition, and then you have to consider if you go 20mm you'll likely want dual feed with a separate AP and HE round like the Germans do with their 20x139 Rh202 which further closes the gap with regards to ammunition weight and volume.
I see the 30x113 as having about the smallest useful HEDP, allowing you to roll with one ammunition type on a platform that's small and light enough (be it an M230, a critter like the ASP, or something else) to be a viable .50 / 40mm replacement on some platforms. I do believe there's still a niche for something even smaller, I'm visualizing the same HEDP projectile as the 30x113, but with a shorter case, firing out of something XM307 sized, which would be less concussive and jarring on softskins while still having a flatter trajectory and lower TOF than the Mk19.
So would 20x102mm. A search found the following weights of 100 rds in steel ammo cans: 12.7x99mm - 35 lbs 20x102mm -- 92 lbs 30x113mm - 110 lbs (estimated weight -- a 30mm ammo can has 110 rds, and weighs 120 lbs)
Kind of an interesting thing I learned recently in terms of 30x113 vs 20x102 - 30mm uses Aluminum cases (~70% lighter then brass) vs Brass for the 20mm.
So even though the 30mm has a shell weight ~2.5x larger, the 30mm is only marginally heavier than 20mm because of its AL case.
I do believe there's still a niche for something even smaller, I'm visualizing the same HEDP projectile as the 30x113, but with a shorter case, firing out of something XM307 sized, which would be less concussive and jarring on softskins while still having a flatter trajectory and lower TOF than the Mk19.
I had actually thought resurrecting the WW2 German MK108 cannon would be a solid sweetspot between MK19 and M230LF.
40x53 = 790fps / 250g shell
30x90rb = 1700fps / 330g shell
You get a big boost in both velocity and HE payload vs 40mm, while still having a smaller / less blasty cannon then the m230lf.
Thing even looks like the MK19:
I have no measured data on either recoil levels or muzzle blast, so your guess is as good as mine.
I read in a manual on urban warfare that Army testing found 20mm didn't penetrate much better than .50.
Depends on which 20mm ammo you are comparing with which .50 cal.
The best 20x102 rounds for penetration will be the APDS developed for the naval Phalanx anti-missile system. The current MK244 as used in the Phalanx 1B looks interesting: it fires a 104.5g 14mm projectile at 1,100 m/s, from longer "optimised gun barrels".
The mk108 or something like the 108 is indeed interesting...
Or just something really cheap that can fire 30x113, that would work too.
Quite a few people have suggested that the fitting a 12.7x99 mm HMG on the UK's Boxer fleet is inadequate. Long-term, it seems likely that a turreted 30x173 mm cannon will be acquired. The question is, what will happen in the short-term?
Short term, I think probably the fastest, cheapest, and most bang for the buck option would be to retain the .50 RWS, and simply mount a coaxial missile system.
Either a Javelin, or the UK's new Martlet Missile, should be pretty straightforward to integrate (not sure what RWS the UK uses for Boxer.)
This 'CROWS-J' Javelin co-ax is what the US Army did to boost the firepower of many of its Strykers, as a response to basically the same set of circumstances presented here with the Boxer. Namely, we need to boost striking power over .50, but don't want to spend the money yet on giving them proper 30x173mm cannons.
Given that the Boxer is essentially the UK's Stryker, its compelling precedent.
And from a danger to the enemy standpoint, I think a .50+Javelin is likely more of a threat to enemy vehicles then a 20x102 or 30x113 cannon. (Of course a 30mm + Javelin + 7.62 gpmg would be the ideal.)
The fielding of the Common Remotely Operated Weapons Station-Javelin (CROWS-J) is part of a larger effort to give the basic Stryker infantry carrier more firepower.
That effort began in March 2015, when commanders began requesting a 30mm cannon to give Strykers more punch than the standard .50 caliber machine guns if they have to face potential adversaries such as Russia.
The UK has apparently already tested this on a different vehicle (the Spartan) and found it very effective:
The British Army sponsored the tests fired from a Kongsberg M151 Remote Weapon Station mounted on a Spartan armored fighting vehicle in Salisbury Plain Training Area in Wiltshire, England.
Each Javelin flew distances between 1.2 and 4.3 kilometers and hit the ground target each time.
"This is important within an expeditionary context where you take everything you need with you and don't get regular resupplies.."
The mk108 or something like the 108 is indeed interesting...
Yeah its very compact for an AC.
MK19 40x53 AGM: 78lbs, 43" long, 16" barrel
MK108 30x90 AC: 128lbs, 41.6" long, 23" barrel
M230LF 30x113 AC: 160lbs, 84" long, (?) barrel
In terms of warhead size, it also launches a 330g shell, which is nearly the payload of the 30x173mm. So for a HEDP Airburst or HE-Frag load it would outperform 30x113, albeit with less overall range / longer time of flight.
I'm curious what the 30x90's powder charge is, and how it would compare in terms of recoil and blast to the 20x102 and 30x113.
This 'CROWS-J' Javelin co-ax is what the US Army did to boost the firepower of many of its Strykers...
A logical way to boost combat power. Glad to see it happening.
I proposed Javelin as IFV armament a quarter of a century ago.