TARKKA-AMPUJAKILTA

Lainaa... high-velocity cannon there is some risk of the shock of impact with the rifling "stripping" the driving band. To combat this, some weapons have progressive rifling, in which the rifling grooves start out parallel then gradually increase in twist down the barrel. In a return to earlier "studded" ...

http://www.takilta.fi/keskustelu/viewtopic.php?f=12&t=808&p=7333&hilit=progressive#p7333

LainaaPerformance improvement experiments with non-standard cartridges



Improvement beyond this standard while still using standard .338 Lapua Magnum brass is possible, but the bullets have to be very long and the normal cartridge overall length of 93.5 mm has to be exceeded. The common 250 mm (1:10 inch) rifling twist rate also has to be tightened to stabilize very long projectiles. Such commercially non-existent cartridges are termed "wildcats". The use of a wildcat .338 Lapua Magnum based cartridge demands the use of a custom or customized rifle with an appropriately cut chamber and a fast-twist bore.



An example of such a special .338 calibre extreme range bullet is the German CNC manufactured mono-metal 18.92 gram (292 gr) LM-105 (G1 BC ≈ 0.93 – this Ballistic coefficient (BC) is calculated by its designer, Mr. Lutz Möller, and not proven by Doppler radar measurements). If Mr. Möller's assumptions are right the LM-105 would have a supersonic range of ≈ 2000 m (2200 yd) at a muzzle velocity of 915 m/s (3002 ft/s) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m³). The LM-105 bullet has an overall length of 54.79 mm (2.157 in) and derives its exceptional low drag from a radical LD Haack or Sears-Haack profile in the bullet's nose area. Rifles chambered for this wildcat cartridge, with a cartridge overall length of 105 mm (4.13 in), and equipped with custom made 180 mm (1] 900 mm (35.43 in) long barrels finished first and second at several long range competitions. Its most recent win (2007) was in an international Special Forces and police sniper competition in Switzerland against rifles chambered for 7.62x51 mm up to .50 BMG at ranges from 100 m – 1500 m (109 yd – 1640 yd). The LM-105 bullet exhibited its very low wind drift susceptibility notably at ranges beyond 800 m (875 yd).[21]



The .343 Lapua Magnum LM-107 is a wildcat cartridge under development based on the standard .338 Lapua Magnum cartridge case[22]. The LM-107 is hoped to boost the ballistic performance of the LM-105 by achieving an increase in supersonic range. The 19.3 g (298 gr) LM-107 projectile is 59 mm long and has a Haack profiled nose and a Adams profiled tail. The rifling twist rate for the .343 Lapua Magnum LM-107 wildcat cartridge will be 180 mm (1 in 7 inch), Ø lands = 8.72 mm, Ø grooves = 8.45 mm and loaded with the LM-107 projectile will have a cartridge overall length of 107 mm. The length of the neck is increased from 8,31 to 8,50 mm to support the bigger LM-107 bullet. Several other dimensions of the .338 Lapua Magnum parental cartridge are also changed. The shoulder angle gets steepened from 40° to 60° and the body taper is set at 1°. The throat area is set at a 2° cone-angle. All this modifications make the .343 Lapua Magnum a fairly comprehensively revised wildcat cartridge. Out of a 900 mm (35.43 in) long progressive twist barrel Mr. Möller expects to achieve 909 m/s (2982 ft/s) muzzle velocity. If Mr. Möller's design assumptions are correct the LM-107 projectile with a calculated G1 BC of 1.02 will offer a supersonic range of ≈ 2170 m (2373 yd) at a muzzle velocity of 909 m/s (2982 ft/s) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m³).

LainaaSiksi lähdimme SO:n kanssa kehittelemään parempaa ja hallitumpaa ase/luotiyhdistelmää silti hyvällä lentoradalla. Ja kas kummaa parempi saatiin aikaiseksi!

Lainaus käyttäjältä: JPuItse suunniteltu sorvattu luoti ja 300 Lapua magnum Sako TRG-S/41 kivääri 94,7mm pitkin ammuksin, normaalilla 655 mm piipulla jossa 10" tavallinen rihlannousu. Aseen kokonaispituus suujarruineen 1200mm, paino 6,5 kg (ilman bipodia), S&B PMII 4-16x50 kiikarilla ja täydellä 5-panoksella lippaassa.



Luodit 10,4g BC 0.69 (tod.näk. enemmän, selvittämättä tarkemmin) ja lähtönopeus 1080 m/s