The 6mm Creedmoor
By Chuck Hawks
Created by competition snipers George Gardner, owner of the GA Precision rifle company, and John B. Snow of Outdoor Life magazine, the 6mm Creedmoor was developed as a long range match cartridge for magazine rifles. It is currently (2017) the most popular caliber in the Precision Rifle Series (sniper rifle) competition.
The 6mm Creedmoor was formed by simply necking-down Hornady's 6.5mm Creedmoor case (itself based on the Hornady designed .30 T/C) to accept 6mm (.243") bullets. Of course, we already have a number of 6mm cartridges offering very similar or superior ballistics. Every 6mm cartridge performance niche has long been filled, but that does not dissuade wildcatters, or ammo companies, from re-inventing the wheel.
A muzzle velocity (MV) of 2960 fps with a 108 grain ELD match bullet puts the new 6mm Creedmoor well ahead of all the small 6mm match cartridges (6mm BR Rem., 6mm PPC, 6x47mm, etc.) and in the same general category as the 6mm Lapua, .243 Winchester and 6mm Remington. Loaded to the same maximum average pressure (MAP), its performance is inferior to the 6mm-284, 6mm-06, 6x62mm Freres and .240 Weatherby Magnum.
The 6mm Creedmoor would undoubtedly have remained just another obscure wildcat cartridge had it not been for the long range shooting and "tactical" (sniping) fad. Suddenly, long range match cartridges are in and names like Creedmoor, Palma and Lapua attract attention and generate consumer interest (also dollars).
The truth is there are no centerfire cartridge niches left worth filling and have not been for a long time. Almost all "new" centerfire cartridges introduced since the 1980s, with only a couple of exceptions (the .17 Hornet and .204 Ruger come to mind), simply duplicate the ballistics of existing cartridges, whether they are named WSM, WSSM, SAUM, T/C, RCM, Creedmoor, Lapua, Palma, Grendel, etc. Just old wine in new bottles, but I digress.
For 2017, Hornady has adopted the 6mm Creedmoor and is offering factory loaded ammunition in the caliber. Ruger is offering the cartridge in their Ruger Precision and American Predator bolt action rifles. Lapua has announced they will offer 6mm Creedmoor brass. Savage intends to chamber for the cartridge. The 6mm Creedmoor has apparently arrived.
The 6mm Creedmoor is a short action cartridge. Its case holds 50 grains of water, compared to 54 grains of water for the .243 Winchester and 47 grains for the 6mm Lapua. The rim diameter is the usual .473". The case head diameter is .470" and the body diameter behind the shoulder is .462", so there is very little body taper to ease extraction. The rather sharp shoulder angle is 30 degrees and the maximum case length is 1.920".
The cartridge overall length (COL) should be about 2.8". (COL may vary, as match cartridges are normally hand-loaded for specific rifles.) For sure, the case uses large rifle primers and standard .243" diameter bullets.
The 6mm Creedmoor case is shorter than the .243 Winchester and 6mm Remington. Long for caliber bullets can therefore be seated somewhat farther out and still work through short action (.308 length) magazines and there is a bit more latitude to accommodate different length barrel throats. This sort of minutiae may matter to competitive long range shooters loading their own ammunition for custom match rifles, but it obviously does not apply to factory loaded ammunition or hunting rifles.
What does matter to any sane shooter is minimizing recoil. Anyone, whether on the firing line or in the field, can shoot better with a rifle that kicks less and smaller caliber cartridges can shoot lighter bullets with the same sectional density, ballistic coefficient and trajectory as heavier bullets in larger calibers that kick harder.
This is why the .243 Winchester has been so popular for so long with young, novice, female and recoil sensitive shooters and hunters. Like the .243 Winchester, the 6mm Creedmoor is a low recoil cartridge. I calculate that, in an 8.0 pound rifle, the Hornady factory load should generate about 9.44 ft. lbs. of recoil energy and a recoil velocity of 8.72 fps. You can see why match shooters would like shooting it.
Here are the Hornady velocity and energy figures for the 6mm Creedmoor with a 108 grain ELD Match bullet (SD .261, BC .536) from a 24" test barrel (velocity fps / energy ft. lbs.):
Here are the Hornady trajectory figures for that load:
Hornady online reloading data for their 108 grain ELD bullet lists several suitable powders. I understand that H4350, Varget and Reloader 22 are popular choices. For example, the minimum load listed with H4350 is 35.4 grains, which is good for a MV of 2700 fps. The maximum load is 40.7 grains and the MV is 3000 fps.
Loads using RL-22 start at 37.2 grains for a MV of 2700 fps and go up to a maximum of 43.8 grains for a MV of 3050 fps. These Hornady reloads presumably use Hornady brass and possibly Federal 210M primers, but this information is not stated on the Hornady website. The test barrel length is also not given, although it is probably 24". Therefore, one should approach maximum loads with all due caution.
Copyright 2017 by Chuck Hawks. All rights reserved.