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Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.

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For Your Amusement   General Army topics

Started 15/9/21 by stancrist; 14517 views.
JPeelen

From: JPeelen

18-Aug

The biggest advantage of a 9 g 6.5 mm bullet is its high sectional density. Based on using real diameter, not caliber, a 7.62 mm bullet would need 12.2 g to achieve the same sectional density. M118LR sniper bullet weight is 11.2 g. 

This is enhanced by an excellent aerodynamic shape for a 1940s ordinary military design, having only 99 percent of drag compared to the G7 standard model. Most modern military bullets are closer to 105-110%.   

Based on Swedish range tables (but using ICAO atmsphere), the m/41 bullet stays supersonic to about 980 m distance, compared to 780 m for the 7.62 M80 (both from a machine gun barrel). The 7.62 M118LR stays supersonic to 950 m.   

Taking 600 m as range example, the m/41 still has a kinetic energy of 1061 J, your 8 g bullet (assuming identical aerodynamics) 964 J and 7.62 M80 has 900 J.  M118LR has 1144 J at this distance.  

An advantage not at all easily expressed in numbers is the significantly(!) reduced felt recol of the Swedish cartridge. A disadvantage in the eyes of modern military is the greater length of the Swedish cartridge, which, as Emeric has noted on this forum, would need longer weapon receivers and result in heavier weapons. 

Disclosure: The above data is computed using ICAO standard conditions and assuming: 

m/41 air drag 99% of G7 drag, based on analysis of Swedish range tables. v0 760 m/s from m/58 (Swedish FN MAG) barrel. Muzzle energy for 9 g and 8 g proposal assumed identical, therefore v0 806 m/s for the 8 g bullet. 

M80 air drag 107% of G7 drag, based on M80 "standard drag function" in report AD-A016865 by Malinoski. This is an average value among those published for M80. v0 830 m/s, bullet 9.5 g.        

7.62 M118LR air drag assumed as 108.5% of G7, as reported by Bryan Litz, v0 777 m/s, bullet 11.2 g.   

  • Edited 18 August 2022 17:11  by  JPeelen
JPeelen

From: JPeelen

18-Aug

Frankly, at the time the association of a Prussian infantry or cavalry general with matters of military technology was akin to him being  associated with a whore. Let alone consideration of cartridge details. Being detailed to a 1 or 2 year tour of studying at the military technological academy was considered an end of career step within infantry, field artillery and cavalry circles. German adoption of machine guns was only possible, because military amateur Wilhelm II insisted repeatedly over the years.        

As far as I can tell from design drawings of the Infanterie-Konstruktionsbüro (infantry design office) in the Bundesarchiv, before WW1 Prussian military was considering a still more powerful(!) 7 mm rifle along the same lines as the British .276 Enfield and the French experimental 7 mm weapons. Alas, we have no details.

The idea of equipping the ordinary soldier with a less powerful hand weapon was stricly a result of WW1 experiences and the replacement of rifle musketry with machine gun fire.           

EmericD

From: EmericD

19-Aug

stancrist said:

Perhaps they did realize it.  6.5x55 AP reportedly had a 7.3 g spitzer boat tail.

OMG!

"The V25 of the 6,5 pprj in a m/96 rifle is 950 m/s (3,117 fps) as compared to the V0 of 8x63 pprj that is 810 m/s (2,658 fps).

The penetration capacity of the 6,5 pprj actually proved to be better than that of the more powerful 8x63mm round. The armor piercing tungsten carbide core of the 6,5mm pprj projectile had a better shape for penetrating hard targets.

Test examples of pprj rounds penetration at 100 meters with a 90 degree impact angle results are:
140 mm of concrete
16-17 mm of HB 500 steel armor.
28 mm of HB 130 steel plate.

In the same test at 300 meters with a 90 degree impact angle the results are:
120 mm of concrete
8 mm of HB 500 steel armor.
22-25 mm of HB 130 steel plate."

schnuersi

From: schnuersi

19-Aug

EmericD said:

Test examples of pprj rounds penetration at 100 meters with a 90 degree impact angle results are:
140 mm of concrete
16-17 mm of HB 500 steel armor.
28 mm of HB 130 steel plate.

In the same test at 300 meters with a 90 degree impact angle the results are:
120 mm of concrete
8 mm of HB 500 steel armor.
22-25 mm of HB 130 steel plate."

These figures are amazing. Even by todays standards they are really good.
While on the hot end for a 6,5x55 the ME isn't that high.

EmericD

From: EmericD

19-Aug

schnuersi said:

While on the hot end for a 6,5x55 the ME isn't that high.

Well, in order to achieve a V25 of ~950 m/s, you need a MV of ~970 m/s (maybe a little more), so that's >3.4 kJ of muzzle energy which seems significantly more than the ~2.9 kJ of the m/41 ball ammo.

But according to the link provided by Stan, the m/41 ball was using only 2.4 g of propellant (a very light load given the case capacity), when the AP was using 3.0 g, so the numbers seems OK.

schnuersi

From: schnuersi

19-Aug

EmericD said:

But according to the link provided by Stan, the m/41 ball was using only 2.4 g of propellant (a very light load given the case capacity), when the AP was using 3.0 g, so the numbers seems OK.

If the standard load was so light could they have shortened the cartridge? Could you make an educated guess what case length would have been possible?

EmericD

From: EmericD

19-Aug

schnuersi said:

If the standard load was so light could they have shortened the cartridge? Could you make an educated guess what case length would have been possible?

Depends on the powder they had available.

In our age where one company like Vithavuori could provide 12 grades of single base powder, it's easy to forget that before WWI (and in some case before WWII) it was a common practice to use extra case capacity to "regulate" the pressure of a powder that was too fast for the bullet weight / diameter.

For example, the lack of a powder slow enough doomed all the French "high velocity" 6 mm & 6.5 mm cartridge programs before WWI, as they needed very large case volume and relatively small powder load.

For example, the best results were achieved with a 6.5 mm cartridge nearly as large as the .270 Wby Magnum, but with a powder load of only 3.6 g, which is not even close to the 4.3 g "starting load" proposed by Vitha for this cartridge...

So, maybe they used this small load because the powder available was slightly too fast, anyway a ~2.4 g load is the maximum load of N540 and N550 that you can use in a 6.5x47 mm cartridge loaded with a 139 gr bullet.

Farmplinker

From: Farmplinker

20-Aug

Thanks for the info! In Sturmgewehr! the author implies Moltke was looking at a 7, possibly 6.5 cartridge that was less powerful than 8x57. Ah well, what could have been...

JPeelen

From: JPeelen

20-Aug

Thank you for mentioning the book "Sturmgewehr" by Dieter Handrich, so I could look up the source text (German edition).

In my view, Moltke's remark regarding reduced recoil of a self-loading rifle shows that he is not really familiar with the subject. The German 7.9 mm has a stiff recoil and any difference between self-loading and manual is theoretical, at least from from the conscript shooter's point of view. (Modern professional soldiers have been whining about the much less recoil of 7.62 NATO.)  

While Handrich does not elaborate, it is known from Morawietz that German engineers saw the power of the 7.9 mm as an obstacle to designing a practical self-loading rifle. But considerations of using a  less powerful cartridge did not at all go so far as the WW1 ideas of a real 300/400 m cartridge. German military considered caliber 6.5 mm as insufficient because lack of wounding power even much later (Deutsch, Waffenlehre, 1939).               

autogun

From: autogun

21-Aug

JPeelen said:

German military considered caliber 6.5 mm as insufficient because lack of wounding power even much later (Deutsch, Waffenlehre, 1939). 

One wonders how much testing took place in coming to that conclusion. During WW2 US medics treating US soldiers hit by small-arms fire were reportedly unable to identify whether the bullets which hit them were 6.5mm or 7.7mm. And of course, there were the "pig board" tests.

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