Military Rifle Cartridges

5.56 NATO, 7.62 NATO, .300 Winchester Magnum, .338 Lapua Magnum, .50BMG

These are the rifle cartridges in common use by modern western militaries. The smallest is the standard NATO infantry round, 5.56x45mm. Adjacent on the left is the “medium” 7.62x51mm, also a common infantry round, especially in theaters where longer engagement distances render the 5.56 ineffective. Middle is .300 Winchester Magnum (.300WM), which has long been fielded for snipers needing to push beyond the 1000-yard “effective” range of the 7.62mm NATO. The .300WM is being supplanted by the fourth cartridge, .338 Lapua Magnum (.338LM), which has emerged as the top long-range military sniping cartridge. Previously, long-range snipers often relied on the largest of the “small arms” cartridges: the century-old “heavy” .50 Browning Machine Gun (.50BMG) round.

The following table lists the size, weight, and range of each cartridge for typical military loads, barrels, and sea-level atmospheric pressure. The point at which bullets slow through roughly 1100fps is a common benchmark for range because that is the speed of sound at typical air temperatures. Historically the accurate range of a precise bullet has been limited by the effects of crossing through the sound barrier. However, modern barrels tend towards faster rifling twist rates which increase transonic stability. In the last decade snipers have recorded first-shot kills at ranges where their bullets were subsonic. Snipers at high altitudes have made a number of remarkable kills at distances of up to 2700yds. The thinner air at high altitudes creates less drag on bullets and thus extends their range.

Caliber Cartridge Weight Length Bullet Energy at 1100fps Standard Barrel Muzzle Velocity Range to 1100fps
MK318 Mod 0 180gr   2.26″   62gr OTM 170 ft-lbs   14″ (M4A1) 2925fps   730 yds  
20″ (M16A2) 3130fps   780 yds  
M118LR 400gr   2.80″   175gr OTM 475 ft-lbs   20″ (M110) 2570fps   970 yds  
24″ (M24A1) 2640fps   1000 yds  
.300WM MK248 Mod 1 490gr   3.50″   220gr OTM 600 ft-lbs   24″ (M24A2) 2850fps   1400 yds  
.338LM 680gr   3.68″   250gr 680 ft-lbs   27″ 3000fps   1525 yds  
730gr   3.85″   300gr 820 ft-lbs   2800fps   1700 yds  
.50BMG M1022 1750gr  5.45″   650gr 1780 ft-lbs   29″ (M107) 2750fps   1500 yds  

On the heavy end it’s interesting to see that the .50BMG is actually at a disadvantage to .338LM in terms of range (not to mention the added weight of the rounds and heavier guns needed to efficiently shoot it). But it does have the capability of delivering more than double the payload, so it is still in use for anti-materiel roles.

One more item that scales with the size of the round is the volume needed to suppress it. A good suppressor reduces the muzzle blast by over 30dB. Here are examples of the size and weight needed to achieve that:

Caliber Suppressor Weight Dimensions Volume
5.56mm Gemtech TREK-T 0.6 lb 1.5×5.7″ 10 in3
7.62mm TBAC 30BA 1.0 lb 1.5×9.0″ 15 in3
.338LM TBAC 338BA 1.5 lb 1.8×10.4″ 26 in3
.50BMG AAC Cyclops 5.0 lb 2.5×15.8″ 77 in3

Shown below are suppressors and rounds for .22LR, 5.56mm NATO, 7.62mm NATO, and .338LM.

Silencers for .22LR, 5.56 NATO, 7.62 NATO, and .338 Lapua Magnum

Notes: Prior to the M118LR the M118 was a 168gr OTM round. M118LR is also specified as MK316 Mod 0, and consists of a Federal case, Gold Medal Match primer, and 41.745gr of IMR4064 powder.

The previous version of .300WM was MK248 Mod 0, which had a 190gr OTM bullet. The Mod 1 specification is notoriously hot, using 77.7gr of H1000 powder, and allowing a peak chamber pressure of 78kpsi!

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