AFV Coax Thread

[Mike E]

Coax definitely wasn't the word I meant to use... A mount similar to the Czech design (ie independent of the gun) might be able to work. I think it is just a matter of the ammunition size, how many rounds can be carried, and if it is really worthwhile. Epoch with the 30 mm auto-cannon and 57 mm grenade launcher will be very interesting.  

[Meplat]

How hard would it be to make a version of the old Browning .30 cal that fired 7.62 NATO?

It was done. The Brits and Canadians had their versions.

[Meplat]

MG-34 looks pretty good as a tank coax, IMO.  Sure, it's a bit sensitive to grit and crap, but it's in a tank so that's less pressing.  It has a barrel you can change from inside the tank without de-mounting the gun, and you don't need to headspace the barrel.

 

Also, unlike the M73, it works.

Pretty much.  A bit long for armor use, but otherwise? They could have done a lot worse.

 

MG-34 is a pretty darn impressive piece of kit when you compare it to other machine guns in use in the mid 30's.  It's an actual real example of quality German engineering.  A bit expensive for wartime production maybe.  What say the firearms experts here?

SOmewhat ammo sensitive, but that was compounded by the often terrible quality of wartime German ammo.

[Khand-e]

Another big reason you saw rifle caliber coax guns was space.

 

There were some oddities where a .50" was tried, but you always saw the fall back to something that did not take up much room, fired a lot of easily stowed cheap ammo that was common with your troops, and could chew up the squishies "good enough".

 

The old M37 variant of the M1919 was about as close to "ideal" as you got with a rifle caliber tank coax.

 

What about the M37 vs a 37mm gun like the M6A1 had? they both have 37 in the name!

[Collimatrix]

Coax definitely wasn't the word I meant to use... A mount similar to the Czech design (ie independent of the gun) might be able to work. I think it is just a matter of the ammunition size, how many rounds can be carried, and if it is really worthwhile. Epoch with the 30 mm auto-cannon and 57 mm grenade launcher will be very interesting.  

 

 

For a really huge secondary cannon, say, 30mm or more, I think you'd actually want it to be coaxial with the man gun.  Ideally, mounted right above it ala the 14.5mm on the IS-7 so that there's no torque on the turret from firing it.  As an added bonus, the smaller weapon wouldn't need its own recoil recuperators; it could re-use the ones from the main gun.

 

This would cause some problems with gun depression unless the secondary gun breech were kept very short, and that's where my idea about a blow-forward weapon comes in.

[Meplat]

What about the M37 vs a 37mm gun like the M6A1 had? they both have 37 in the name!

[Collimatrix]

Domestic Armored Vehicles mentions that prior to the adoption of the PKMT, Soviet designer VI Silin had a design for a dedicated tank coax MG that would put empty casings back into the belt, so as to keep all that brass from making a mess in the turret and getting into things.  Hilariously, at one point Google Translate auto-translated whatever the Russian for "machine gun belt" is as "gun food."

[Priory_of_Sion]

Why can't we go back to the days when ~37 mm cannons were the main weapon instead of being the coax?

[Khand-e]

Why can't we go back to the days when ~37 mm cannons were the main weapon instead of being the coax?

 

And have a 125mm autocannon for a Coax instead? I like this idea.

[Priory_of_Sion]

And have a 125mm autocannon for a Coax instead? I like this idea.

Somebody gets it!

[LoooSeR]

Domestic Armored Vehicles mentions that prior to the adoption of the PKMT, Soviet designer VI Silin had a design for a dedicated tank coax MG that would put empty casings back into the belt, so as to keep all that brass from making a mess in the turret and getting into things.  Hilariously, at one point Google Translate auto-translated whatever the Russian for "machine gun belt" is as "gun food."

Translation is actually right, because we use word "питание" when describing automatic weapon feed system. Hell, "feed" also can be used in context of food, after all.   

[LoooSeR]

Moderna photos via otvaga:

 

 

 

 

 

 

 

 

 

 

[Collimatrix]

Reposting this here:

 

Twin roof-mounted KPVTs, because your commander is going to want something serious to fight with if he needs to unbutton and use the roof gun!

[Khand-e]

Why not just use the 14.5mm variant of the Slostin gun like what was planned for the IS-7?

[Collimatrix]

There were a bunch of notional roof weapons mounts scribbled on paper for IS-7.  Some had a single KPV, some had a mix of KPVs and SGMTs.  For all I know the gatling mount was another planned version, but TBH the only place I recall reading that they planned to put a 14.5mm gatling on the roof of the IS-7 is wikipedia, so I am skeptical.

 

But it doesn't seem impossible.  The secondary armament of the IS-7 was complete insanity, so putting a huge gatling on the roof doesn't seem that far fetched.

[roguetechie]

On 8/29/2015 at 7:39 PM, Walter_Sobchak said:

How hard would it be to make a version of the old Browning .30 cal that fired 7.62 NATO?

Walter, 

I have the blueprints for the Canadian 7.62 NATO M37retrofit if you want them let me know.

Sidenote: the Browning 1919/m37 is just outright an awesome gun that you can get to run just about any round between .22 lr and 8x63 Bofors...

Including 303 & x54r... I helped a buddy do a x54r version...

Fun fact: the Finns even figured out a really simple push feed link to convert mg42's to x54r... Aimo Lahti was a genius.

[Collimatrix]

I had seen a picture of that converted MG-42 and wondered how in the hell it worked.

[FORMATOSE]

AMX-30 M693 20mm autocannon superelevation (-8° to +40°) :

 

[Vicious_CB]

Ive been mulling over this topic for a while so it was a boon that I found this forum. Being mostly a small arms guy I admit that I know very little about AFV design. I was always puzzled why the 7.62 was the coax caliber of choice when the advantages of the heavy MG in range, barrier defeat and actually being able to take advantage of the FCS of an AFV without the main con of weight that infantry have to deal with.The only downside being volume. Im pretty sure a proper FCS makes a .50 cal far more effective than Joe aiming with the tip of barrel and walking the tracers into the target. But which heavy MG? I feel like the M2HB ROF is too low for a proper beaten zone at range. Maybe a AN/M2 or even a M3M at 1,100 rpm?

 

Also how does the new M230LF fall into the coax discussion?There are talks of it replacing the M2A1 and Mk19 on RWS or even vehicle mounts. Would it make a viable coax? How about it replacing the M2 on the TC's CROWS?

 

http://warfaretech.blogspot.com/

[Xoon]

30 minutes ago, Vicious_CB said:

Ive been mulling over this topic for a while so it was a boon that I found this forum. Being mostly a small arms guy I admit that I know very little about AFV design. I was always puzzled why the 7.62 was the coax caliber of choice when the advantages of the heavy MG in range, barrier defeat and actually being able to take advantage of the FCS of an AFV without the main con of weight that infantry have to deal with.The only downside being volume. Im pretty sure a proper FCS makes a .50 cal far more effective than Joe aiming with the tip of barrel and walking the tracers into the target. But which heavy MG? I feel like the M2HB ROF is too low for a proper beaten zone at range. Maybe a AN/M2 or even a M3M at 1,100 rpm?

 

Also how does the new M230LF fall into the coax discussion?There are talks of it replacing the M2A1 and Mk19 on RWS or even vehicle mounts. Would it make a viable coax? How about it replacing the M2 on the TC's CROWS?

 

 

The AN/M2 and the M3 are aircraft mounted, slip stream cooled HMGs, with thinner, lighter barrels.  It would overheat very quickly and would need to be down rated to below the normal M2.

If you want a higher rate of fire you would need a thicker barreled version, or a water cooled version. Maybe the FN M3P could work?

[Xlucine]

Volume is a major penalty for a .50 - the ammunition takes up a lot more space. Typical coax installations can take a belt that's several thousand rounds long, and a belt long enough for an equal length of time firing with a .50 would need several times more volume

[Belesarius]

3 hours ago, Vicious_CB said:

Ive been mulling over this topic for a while so it was a boon that I found this forum. Being mostly a small arms guy I admit that I know very little about AFV design. I was always puzzled why the 7.62 was the coax caliber of choice when the advantages of the heavy MG in range, barrier defeat and actually being able to take advantage of the FCS of an AFV without the main con of weight that infantry have to deal with.The only downside being volume. Im pretty sure a proper FCS makes a .50 cal far more effective than Joe aiming with the tip of barrel and walking the tracers into the target. But which heavy MG? I feel like the M2HB ROF is too low for a proper beaten zone at range. Maybe a AN/M2 or even a M3M at 1,100 rpm?

 

Also how does the new M230LF fall into the coax discussion?There are talks of it replacing the M2A1 and Mk19 on RWS or even vehicle mounts. Would it make a viable coax? How about it replacing the M2 on the TC's CROWS?

 

 

Welcome to SH!

 

 

[Collimatrix]

6 hours ago, Vicious_CB said:

Ive been mulling over this topic for a while so it was a boon that I found this forum. Being mostly a small arms guy I admit that I know very little about AFV design. I was always puzzled why the 7.62 was the coax caliber of choice when the advantages of the heavy MG in range, barrier defeat and actually being able to take advantage of the FCS of an AFV without the main con of weight that infantry have to deal with.The only downside being volume. Im pretty sure a proper FCS makes a .50 cal far more effective than Joe aiming with the tip of barrel and walking the tracers into the target. But which heavy MG? I feel like the M2HB ROF is too low for a proper beaten zone at range. Maybe a AN/M2 or even a M3M at 1,100 rpm?

  

Also how does the new M230LF fall into the coax discussion?There are talks of it replacing the M2A1 and Mk19 on RWS or even vehicle mounts. Would it make a viable coax? How about it replacing the M2 on the TC's CROWS?

 

 

The primary constraining factor in tank design is volume.  A tank is about 50% armor by weight, and armor is by far the single heaviest part of a tank.  Making components larger and bulkier adds a lot of weight indirectly because it increases the volume that needs to be protected by armor.

 

So, the most compelling argument for a more powerful coax on a tank is that the coax can be used to zap less armor targets like infantry, unarmored vehicles, etc, and so economize on the use of main gun ammunition, which is gigantic.  But this idea has been challenged too; early on in the development of the M1 Abrams there was an idea to have a coaxial 25mm autocannon.  Apparently the actual armor combat experience from the Middle East suggested that anything vaguely vehicle-shaped got serviced with the main gun.  There may be more to this, but I've only read that much.

 

There are other issues with large-caliber coaxes.  The area where the main gun protrudes from the turret of the tank is a weak point, and adding a large secondary weapon only makes this weak point wider.  There is also the problem that autocannons produce substantial recoil, to the point where they can jerk the turret off-target if they are mounted too far from the centerline of the turret.

 

That said, a few tanks have had large-caliber coax weapons.  The French Leclerc has a .50 coax, and a number of Russian heavy tanks had 14.5mm coaxes (which were a close match to the ballistics of the main gun and helped walk in rounds).  I'm sure there are other examples in this thread.

[LostCosmonaut]

The Strv 2000 proposal had a "coax" 40mm gun, although that doesn't count 100% since the main gun was designed exclusively for use against vehicle targets (the autoloader was designed to only feed APFSDS rounds for simplicity).

[Vicious_CB]

11 hours ago, Collimatrix said:

 

The primary constraining factor in tank design is volume.  A tank is about 50% armor by weight, and armor is by far the single heaviest part of a tank.  Making components larger and bulkier adds a lot of weight indirectly because it increases the volume that needs to be protected by armor.

 

So, the most compelling argument for a more powerful coax on a tank is that the coax can be used to zap less armor targets like infantry, unarmored vehicles, etc, and so economize on the use of main gun ammunition, which is gigantic.  But this idea has been challenged too; early on in the development of the M1 Abrams there was an idea to have a coaxial 25mm autocannon.  Apparently the actual armor combat experience from the Middle East suggested that anything vaguely vehicle-shaped got serviced with the main gun.  There may be more to this, but I've only read that much.

 

There are other issues with large-caliber coaxes.  The area where the main gun protrudes from the turret of the tank is a weak point, and adding a large secondary weapon only makes this weak point wider.  There is also the problem that autocannons produce substantial recoil, to the point where they can jerk the turret off-target if they are mounted too far from the centerline of the turret.

 

That said, a few tanks have had large-caliber coax weapons.  The French Leclerc has a .50 coax, and a number of Russian heavy tanks had 14.5mm coaxes (which were a close match to the ballistics of the main gun and helped walk in rounds).  I'm sure there are other examples in this thread.

 

 

Thanks for the warm welcome guys. Hope I can contribute with my limited knowledge base. 

 

I see. So a M230LF coax is probably out the question since its eating up too much space inside the turret. In terms of ammo volume 7.62 vs .50 cal, I know the M1 Abrams particularly carries an absurd amount to coax ammo comparably to other tanks, something like 10,000 rounds. Im not quite sure what ratio would be if you swapped 7.62 to .50 cal(2:1?3:1?) you would probably still have as much coax ammo as other MBTs. Also logistically .50 cal is very common in both light infantry and with the stryker guys so there would be no shortage there. 

 

As far as gunners lighting everything up with main gun, isnt that a training issue? Like we say in the shooting community,  sounds like a software issue not a hardware issue. Something like a technical probably doesnt warrant a main gun round. .50 cal API also makes swiss cheese out of double reinforced concrete walls that can easily stop 7.62 SLAP. Also Ive heard more than few times in Helmand where USMC tanks on overwatch were unable to support their infantry clearing a compound due to the fears of some devil dog catching a sabot petal in the back of the head. I have no idea what the danger space is when firing a saboted round is but Ive heard its a real issue when supporting infantry. 

 

Maybe the answer is stick a M230LF on the commanders CROWS? if you used the CROWS-LP it probably wouldnt be much larger than the CROWS /w M2HB(height wise) than we have now. The question is where to store all the ammo. Now at least you have some HE throwing capability when infantry are within the danger space of the main gun. 

 

If volume is an issue the most space efficient system would be the .338 NM LWMMG from General Dynamics. .50 cal range in a M240 package though it probably doesnt have the same barrier defeat capability as a .50 cal slug. Supposedly the 160th SOAR is interested in this round to replace their .50's with this which makes sense in aviation where take off weight is a huge issue where less weight = more time on station before going winchester bingo.  

 

Vehicle wise you can probably get away just swapping the M240 with the .338 LWMMG since they are similarly sized where a M2 would probably call for a redesign of the mantlet.