Hi i had an idea for a military cartridge in the .18cal range (4.65mm)

This would be given extreme, M4 esque energies from long barrels....and present a difficulty in stabilising the 47grn bullets.

Anyway to eliminate the inevitable barrel wear problems, i wondered if it would help to use the advanced modern stuff, like the hammer forged barrels on daniel defence guns.

I also considered sabots...im sure their poor accuracy in the 1980s tests was due to the very light projectiles. Ultimately i would require flawless 600m accuracy.

 Quality control is the main issue with sabots.

So yeah, any thoughts....

My main question is about rhe barrel wear.....also, do these advamced materials make the barrel heavier than usual?

What is the L/D ratio of the bullet you want to launch?

Diameter matches the MP7 round...4.65.

Length would.be around 25mm like the russian 545 or 224 valkyrie.

I dont think the l/d ratio would be related to barrel wear....other than bearing surface amount.

Well there is no reason to change unless the round does something special and no reason to go that small unless the reason is velocity.

One of Emeric's old copper projectiles was 6.5 mm and 6.8 grams for a BV of .235. Scaled down to 4.7 of so that gives us a BC of  .164 and a mass of just over 2 grams.  Now in a case like the .224 Valkyrie that gives scope for around 1200 mps though barrels will need to be a bit longer than the current fashion. No AP to speak of but it will be much flatter and with a shorter time of flight out to 800 metres or so. The only question is barrel wear.

Right. My energy requirement was 1100lbs (21 inch barrel approx)

With that energy, a 6.5mm projo would have awful performance. (or even a .22)

I did wonder how 4.6mm would fare compared to .20 or .19 cal, but the real thing i was wondering was about the barrel wear being reduced with advanced materials.

smg762 said:

I dont think the l/d ratio would be related to barrel wear....other than bearing surface amount.

You're right that there is no direct relationship between a bullet L/D and barrel wear, but if you want to use a projectile with a ~5.4 L/D, then saboted bullet are simply not an option.

ok. I wasnt too keen on sabots anyway...but i heard they actually allow a longer l/d bullet than normal rifling.

smg762 said:

ok. I wasnt too keen on sabots anyway...but i heard they actually allow a longer l/d bullet than normal rifling.

Nope, they have a negative impact not a positive one. Unless you have a sintered tool steel projectile which is coke bottle shaped and VLD, there is no point. 

Even then a crimped on copper sleeve would be more accurate and practical.

Sabots allow a fin stabilised projectile which means you can have a higher L/D ratio.

Technically you can have fins on the tail of a full-bore projectile, but needs a longer tail/bigger fins to be effective. Or you go for deploying fins, which are a nuisance in large calibre and probably impractical in small ones

Perhaps perfect sabot açcuracy (in small arms) could be achieved if you tried to take the exact proportions of a tank APFDS, (projectile weight versus muzzle energy).....

..and EXACTLY scale them down.

Tank flechette penetrators are 4.5kg each....sabot is roughly 3kg...

I dunno the energies though. Perhaps someone who knows could then do the math and work out how much a rifle projo would weigh.

Clearly more than 10grains as used in the ACR trials

Problem is tanks have no weight targets to reach....everythings very heavy

To match those proportions would probably mean a package weighing similar to 308 battle rifles