The 6.5mm Grendel
By Chuck Hawks
The 6.5mm Grendel was designed as a cartridge for long range precision shooting with AR15 type rifles. It is basically a match cartridge and, to a lesser extent, a hunting cartridge.
Bill Alexander of Alexander Arms developed this short, squat 6.5mm cartridge. Alexander Arms is now (as I write these words in 2005) offering ammunition and rifles in 6.5mm Grendel caliber. Unfortunately, as far as I can determine (the Alexander Arms web site is very limited in scope), these are only military style match/sniper rifles on the AR15 platform, which are of limited utility to mainstream hunters and shooters.
The AR15 rifle imposed severe constraints on the 6.5mm Grendel's design in the areas of back thrust, pressure (MAP 45,000 psi), and cartridge overall length. The new cartridge had to function safely in an action designed around, and feed through a magazine intended for, little .223 Remington cartridges. These compromises would not have been necessary had the 6.5mm Grendel been designed to function in strong, civilian rifle actions such as Browning's autoloading BAR, lever action BLR, and bolt action A-Bolt II.
Freed of the constraints imposed by the AR15 rifle platform, a more versatile and effective 6.5mm cartridge design would have been possible. That was the approach taken by A-Square and Remington that resulted in the 6.5mm-08 A-Square, which was released commercially as the .260 Remington. But that cartridge was designed with normal short action (.308 length) civilian rifles in mind, like the Browning's mentioned in the paragraph above, which are capable of routinely operating at a maximum average pressure (MAP) of 60,000 psi or more.
As the model for case design, Alexander chose the 6mm PPC, necked-up to accommodate standard .264" diameter bullets. This case eventually proved to be well suited to his needs.
A prototype 6.5mm Grendel rifle was completed and demonstrated in 2003. Lapua (the Finnish ammunition maker) engineers assisted Alexander with modifications intended to optimize the case for use with 107-130 grain bullets, which included a longer shoulder and a shorter neck.
Most of the 6.5mm Grendel's case dimensions remain similar to those of the parent PPC case. The case length is 1.505", rim diameter is .442", rim thickness is .050" and head diameter is .445". The PPC's basic case shape was retained. Capacity is about 35 grains of water. Cartridge overall length is 2.255" and bullet diameter is .264" (6.5mm). MAP is about 42,000 psi. (The permissible MAP for the AR15/M16 action is only 45,000 psi, according to Alexander, so do not attempt to develop high-pressure loads for the 6.5mm Grendel cartridge.)
The intrinsic accuracy of the 6.5 Grendel is alleged to be excellent. It is worth remembering that U.S. soldiers in the Pacific Theatre during WW II found the accuracy of the 6.5x50 Japanese service round, a cartridge offering very similar ballistics to the 6.5mm Grendel, to also be very good. Accuracy is a trait long associated with moderate 6.5mm cartridges.
Alexander Arms offers 6.5mm Grendel ammunition factory loaded with 90 grain Speer TNT varmint bullets, Nosler 120 grain Ballistic Tip hunting bullets, and Lapua 123 grain Scenar match bullets. This ammunition is loaded using Lapua brass with an Alexander Arms headstamp and costs $20/box (20 rounds) online from Competition Shooting Sports. Alexander Arms also offers 6.5mm Grendel reloading dies made by Lee Precision ($44/set from Competition Shooting Sports).
The 120 grain Nosler Ballistic Tip bullet has a ballistic coefficient of .458 and a sectional density of .246. Here are the velocity/energy figures for that bullet as factory loaded for the 6.5mm Grendel: Muzzle - 2600 fps/1801 ft. lbs.; 100 yards - 2413 fps/1551 ft. lbs.; 200 yards - 2234 fps/1330 ft. lbs.; 300 yards - 2062 fps/1133 ft. lbs. At a MV of 2600 fps the trajectory of that bullet looks like this: +2.8" at 100 yards, +1.1" at 200 yards, -7.5" at 300 yards. The maximum point blank range of that load (+/- 3") is 259 yards.
Here are some hunting reloads developed by David M. Fortier and first published in Shooting Times Magazine. Mr. Fortier used Lapua brass and Federal Gold Medal Small Rifle Match primers for all loads:
Hornady 100 grain SP bullet, 30.0 grains Western Powder X-Terminator, COL 2.25", MV 2807 fps.
Nosler 120 grain Ballistic Tip bullet, 31.0 grains AA2520 powder, COL 2.26", MV 2636 fps.
Cartridges of this class are adequate for taking most CXP2 class game, such as European and North American deer. Shooters should welcome any new cartridge that combines adequate trajectory, killing power, and accuracy with low recoil.
Note: A full length article about the 6.5mm Grendel can be found on the Wildcat Cartridge Page.
Copyright 2005, 2013 by Chuck Hawks. All rights reserved.