History
C.I.P. standardized the .300 Lapua Magnum in 1989, with Finland as the country of origin. It is the big, beltless .338 Lapua case necked down to .308 inch, built to drive the heaviest, highest-BC .30 caliber match bullets flatter and through less wind than the .30 magnums on smaller brass.
The .338 Lapua found a factory-ammunition following. The .300 never did. The later .300 Norma Magnum matched most of its ballistics on a shorter, more efficient case and took the off-the-shelf ELR market outright. What survives is a handloader's round, kept alive by shooters already running the .338 Lapua case who want a .30 caliber option from the same brass family.
Lineage
From the .338 Lapua it inherits the beltless, rimless head and a roughly 20 degree shoulder, and it feeds from a magnum-length action on a large rifle magnum primer. The parent .338 Lapua descends in turn from the .416 Rigby. Its peers are the other big .30 caliber ELR rounds: the .300 Norma Magnum, .300 PRC, .30-378 Weatherby, and .300 Remington Ultra Magnum.
Specifications
| Spec | Value |
|---|---|
| Case type | Rimless, beltless, bottlenecked (~20° shoulder) |
| Bullet diameter | 7.82 mm (.308 in) |
| Neck diameter | 8.73 mm (.344 in) |
| Shoulder diameter | 13.82 mm (.544 in) |
| Base diameter | 14.91 mm (.587 in) |
| Rim diameter | 14.93 mm (.588 in) |
| Case length | 69.20 mm (2.724 in) |
| Overall length | 94.50 mm (3.720 in) |
| Case capacity | ~96 gr H2O (nominal) |
| Primer size | Large rifle magnum |
| Belted | No |
| Rifling twist (C.I.P.) | 1 in 9.4 in (240 mm) |
| Max pressure | C.I.P. 4,400 bar (440 MPa, ~63,800 psi) |
| Recommended barrel | 32 in, 1:9 twist |
Dimensions are taken from the C.I.P. TDCC datasheet for the .300 Lapua Mag (cartridge maximum). C.I.P. headspaces on the shoulder and prints no datum circle, so the datum line on the cutaway is a derived mid-shoulder reference, not a published gauge dimension.
Barrel Design
The barrel logic here is all about keeping the heaviest .30 caliber match bullets stable and fast to distance. I set my twist at 1:9, a touch faster than the C.I.P. standard 1:9.4, to hold a comfortable stability margin on the 215 to 250 grain bullets through the transonic range where it matters most.
This is a large, overbore magnum, and a long barrel lets its slow powders finish burning. The baseline I'd recommend is 32 inches, which collects the velocity without pushing into the unwieldy. Barrel life is the expected cost of a case this overbore: throat erosion will walk your accuracy node out over the low thousands of rounds, so treat the barrel as a consumable on a serious ELR rifle.
The tables below are computed at that 32 inch barrel from representative handloads. There is no common factory .300 Lapua ammunition, so confirm your own load on a chronograph before trusting any dial.
Handload Performance
Handload · 230 gr Berger Hybrid Target
| Range (yd) | Velocity (fps) | Elevation (mil) | Energy (ft-lb) | Windage (mil) |
|---|---|---|---|---|
| 0 | 3050 | -0.3 | 4750 | 0.3 |
| 100 | 2930 | 0.0 | 4384 | 0.1 |
| 200 | 2812 | -0.3 | 4039 | 0.3 |
| 300 | 2697 | -0.8 | 3715 | 0.4 |
| 400 | 2584 | -1.4 | 3411 | 0.5 |
| 500 | 2474 | -2.1 | 3127 | 0.7 |
| 600 | 2367 | -2.8 | 2861 | 0.8 |
| 700 | 2262 | -3.5 | 2614 | 1.0 |
| 800 | 2161 | -4.3 | 2384 | 1.2 |
| 900 | 2062 | -5.2 | 2171 | 1.3 |
| 1000 | 1965 | -6.1 | 1972 | 1.5 |
| 1100 | 1871 | -7.1 | 1787 | 1.7 |
| 1200 | 1779 | -8.1 | 1616 | 1.9 |
| 1300 | 1688 | -9.3 | 1456 | 2.1 |
| 1400 | 1600 | -10.5 | 1308 | 2.4 |
| 1500 | 1514 | -11.8 | 1171 | 2.6 |
| 1600 | 1430 | -13.2 | 1044 | 2.9 |
| 1700 | 1348 | -14.8 | 928 | 3.2 |
| 1800 | 1269 | -16.4 | 823 | 3.5 |
| 1900 | 1194 | -18.2 | 728 | 3.8 |
| 2000 | 1125 | -20.2 | 646 | 4.1 |
| 2100 | 1081 | -22.4 | 596 | 4.5 |
| 2200 | 1052 | -24.7 | 565 | 4.8 |
| 2300 | 1028 | -27.2 | 539 | 5.2 |
| 2400 | 1006 | -29.9 | 517 | 5.6 |
Muzzle velocity 3050 fps is the factory figure from a 32 in test barrel. Expect your own barrel to read a little differently. Velocity is color coded green supersonic, yellow transonic, red subsonic; treat transonic and subsonic rows as approximate.
Trajectory
FAQ
What barrel length and twist should I run?
A 1:9 twist for the heavy 215 to 250 grain .30 caliber match bullets the cartridge is built around (slightly faster than the C.I.P. standard, for stability margin), and a 32 inch barrel to collect its velocity. This is an ELR build; a shorter barrel gives up the reach that justifies running a case this size.
Is the .300 Lapua Magnum a SAAMI cartridge?
No. The .300 Lapua Magnum is standardized by C.I.P. rather than SAAMI, with Finland as its country of origin. The dimensions on this page come from the C.I.P. TDCC datasheet. Because C.I.P. headspaces on the shoulder, there is no published datum circle; the datum shown on the cutaway is a derived mid-shoulder reference.
How does it compare to the .300 Norma Magnum?
They land in very similar performance territory with the heaviest .30 caliber bullets. The .300 Norma reaches it on a shorter, more efficient case and, crucially, has real factory ammunition and widespread ELR support, which is why it won the market. The .300 Lapua makes most sense for a handloader already invested in the .338 Lapua case who wants a .30 caliber companion.
Is there factory ammunition?
Not in any practical sense. The .300 Lapua Magnum is a handloader's cartridge; you form or buy brass from the Lapua case family and load it yourself. Shooters who want an off-the-shelf .30 caliber ELR cartridge generally choose the .300 Norma Magnum or .300 PRC instead.