Thoughts on 8 mm Kurtz, 7.62 x 39, and 6.8 mm.

[A Guy Out West]

Which would make the best military assault rifle caliber? I think the Germans had it nailed back in the 1940s.

 

[Laurie]

Actually, I'd argue the British / Belgiums / Canadians had it nailed Ca. 1950 with the .280/30 British aka 7X43mm aka 7mm Mk1z aka 7mm NATO aka 7mm FN Short and a few more names to boot. Throw in the original superb 1950s FN FAL (Fusil Automatique Leger) which really was (full auto / selective fire) automatic and light unlike the final long, heavy, and semi-auto version dictated by the adoption of the over-powerful US T65E3 / 7.62 NATO cartridge.

 

[A Guy Out West]

Never heard of that one Laurie. One of the reasons I like this site, actually lean a few things here.

 

[A Guy Out West]

Actually, I'd argue the British / Belgiums / Canadians had it nailed Ca. 1950 with the .280/30 British aka 7X43mm aka 7mm Mk1z aka 7mm NATO aka 7mm FN Short and a few more names to boot. Throw in the original superb 1950s FN FAL (Fusil Automatique Leger) which really was (full auto / selective fire) automatic and light unlike the final long, heavy, and semi-auto version dictated by the adoption of the over-powerful US T65E3 / 7.62 NATO cartridge.

Looked it up, no doubt the British round has better ballistics, however it has a COL of 65 mm vs the Kurtz of 48 mm. Advantage of he German round would be you could carry more ammo and have a smaller lighter gun. Trade offs in everything.

 

[hybridfiat]

Current research and development on the 'Ideal' cartridge and caliber are swinging between the 6.5mm for it's inherent accuracy and the 7mm for downrange kinetic energy delivery so a compromise is likely, the 6.8mm.
The cartridge will be a Kurtz probably a cartridge based on a Rem .30cal or similar. This keeps weight and bulk down allowing a larger number to be carried and loaded.
The 6.8 SPC has been trialed by the Americans and would be acceptable but the forces are not keen on the expense of changing all their weapons. Instead they have gone for improving the projectile used in the 5.56x45 NATO. Not sufficient as many who have fought in Afghanistan will testify. The round simply hasn't got the authority at 300m+ for suppressing fire to keep the enemy's head down or to knock them off.

 

[hybridfiat]

Laurie, I loved my SLR L1A1 but we were hampered by it's semi auto ability. For a while the addition of a piece of matchstick below the sear rendered it full auto but as with the later (With it's official 'piece of matchstick') L2A1 the rifle was uncontrollable, uncomfortable and undesirable.

 

[A Guy Out West]

8 m Kurtz 123 gr. @ 2250 - 1940s
6.8 SPC 120 gr. @ 2460 - 2002

Wonder what he Kurtz would do if necked down to .27?

 

[Greener Jim]

I'd be more interested in what would happen if you bumped the Kurtz up the 10 Ksi it's down compared to modern cartridges. Same for the 7.62x39 for that matter.

 

[hybridfiat]

You could try it. The German case is available and a custom reamer from Manson Reamers in America doesn't cost that much. Dies will though.
Lots of sizing down and neck reaming needed but it would be an interesting wildcat. The case would be very strong so in a strong short action, loads could be pushed to the limit. Has anyone got a copy of Barnes Cartridges of the World to hand? I'm on the mine so can't look to see if this has been done.

 

[hybridfiat]

The Kurtz has a greater capacity than the 5.56 x 45 so I'd say loads would be aprox that of the 6.8 SPC. Capacity is the major factor in load development if projectile weights and action strength are equivalent.
I used to do wildcats so my approach to load development may seem a bit cavalier to some. Remember when doing a new case and load there ARE no references or precedents to help. So approximation, a cradle and a long piece of string round the trigger are the norm.

Addit: I've just had a look at the relative case capacities of the 7.62 x 39 and the Kurtz and they are very very close. I'd say that given a steep shoulder (improved) angle the Kurtz would be the same. So you would be wasting time playing with it. Use a PPC case instead.
To see what kind of results can be got from this case go to information on the 220 Russian and the .22, 6mm family of PPC cases.

 

[Greener Jim]

I do, just had a look and can't see owt that uses it as a parent. 30 Kurz by Barnes comes close as it's just a severely shortened 308/30-06 case.

 

[Greener Jim]

The Kurtz has a greater capacity than the 5.56 x 45 so I'd say loads would be aprox that of the 6.8 SPC. Capacity is the major factor in load development if projectile weights and action strength are equivalent.
I used to do wildcats so my approach to load development may seem a bit cavalier to some. Remember when doing a new case and load there ARE no references or precedents to help. So approximation, a cradle and a long piece of string round the trigger are the norm.

I'll have a look on quickload for a rough approximation. Necked up to.338" or .366" would be interesting as well

 

[hybridfiat]

Last of all I made a 6mm 30-30 rifle using the 30-30 shortened to 1.5". Original case taper as it had to feed into a Martini Cadet action and an improved shoulder. Very close to the Kurtz in capacity and performance was excellent. It was a very efficient cartridge. Very little powder and low weight very good velocity using the lighter projectiles (70gn -85gn).
I didn't keep it as someone wanted the action in another more easily fed caliber (.357 Maximum).

 

[hybridfiat]

I'll have a look on quickload for a rough approximation. Necked up to.338" or .366" would be interesting as well

The .357 maximum case is a good one to use in applications like this. I've still got a custom built Martini Cadet chambered in .224-.357max. Thats a .357 max case necked down in a 221 fireball FLR die to .224 and neck turned. It gives velocities (only with light projectiles >50gn) so close to the .222 Rem that they are indistinguishable.
Necked to .338 it would be a very good candidate for a 'Whisper' rifle. Fast twist, long heavy projectile and sub sonic velocities.

No No No I have far too much to do now I cannot be distracted by more projects, I'm on the (wildcat) wagon.

 

[Muir]

I do, just had a look and can't see owt that uses it as a parent. 30 Kurz by Barnes comes close as it's just a severely shortened 308/30-06 case.

I briefly has a 308x1.5 Barnes. I have thought that if someone wanted to make a sub sonic round for the new Ruger Precision Rifle it would be just the thing.~MUir

 

[Greener Jim]

I haven't seen the Howa Mini in the flesh but it'd be a nice start for a Kurz variation. That's if the bolt face has enough meat to open it up to Mauser size.

 

[Muir]

How about the 300 AAC Blackout? I just bought 1000 Federal 130 grain SOST HP Match bullets. I'm looking forward to spanking them out around 2200 fps. I've never shot them but rumor is they are nasty on the receiving end.~Muir

 

[Reiver Boy]

How about the 300 AAC Blackout? I just bought 1000 Federal 130 grain SOST HP Match bullets. I'm looking forward to spanking them out around 2200 fps. I've never shot them but rumor is they are nasty on the receiving end.~Muir

The 300Blk is getting quite a bit of face time today, I predict the rifle builders round the UK will start getting more and more enquiries over the next few months. Go on, give that old .222/.223 a new lease of life and stick a 14" 300Blk chambered barrel on it

 

[A Guy Out West]

How about this one, a 6 x 45 mm 75 gr. @ 2700 fps. The US Govt. could just get new uppers and we could have a much more effective military rifle than the M16. While they were at it, they could also switch to a gas piston system. A guy could still carry 660 rounds without too much trouble.

 

[bewsher500]

read this
hard to argue with sheer uptake and usage
good read