Overbore Addiction: The Big 224s Member Robert Coles LOAD for maximum case capacities
(overfl ow grains in H2O) and will list them from least to greatest: 1. 22-250 A.I. = 46.90 2. 22-243 = 50.00
3. 22 CHeetah MK I = 54.00 4. 22 CHeetah MK II = 56.00 5. 220 Swift A.I. = 57.00 6. 22 Clark = 59.00 7. 22-284 = 61.84
22-250 A.I. Another P.O. Ackley success with
his classic blown-out case and 40-degree shoulder. Velocities will push to 4,000 fps and the case has an effective range out to 500 yards. Reduced bolt thrust and case stretch, along with the ability to chamber and shoot factory 22-250 loads, make this extremely accurate round a versatile choice.
22-243
Big cases, heavy bullets, slow burning powder, and fast twist barrel combine to make a satisfactory "big boomer" for oversize 22 caliber cartridges.
rel burner cartridges.” You know the talk: “You’ll replace that barrel in 600 rounds.” “Better have a good supply of extra barrels on hand.” “The barrel makers will love you.” As avid varmint shooters (that’s why you are reading this … right?) we all know too much heat to a barrel will produce an eroded throat. The 220 Swift was an example of this. However, shooters proved that example may not be true with proper loading recipes and keeping down bar- rel overheating by pacing your shots. While shooting my 22-250 and 22
T
BR I eventually became interested in the big 224s. Sure, I can push my 22-250 to 4,000 fps with 40-grain woodchuck medicine. But out around 500 yards bullets are suffering the effects of wind and drift. I had copies of “Wildcat Cartridges” Volumes 1 and 2 by Wolfe Publishing and became intrigued with the examples of 224s pushing 80-grain bullets well into the 1,000-yard range. These dedicated purpose cartridges are developed for long range shooting where long and heavy .224" bullets are used to buck the wind better and retain
Page 92 Winter 2012
his is an overview on a subject that has been dubbed “bar-
their energy out to extreme distances. How this is done is sort of confusing to reloaders since fast twist barrels will most likely shoot best with fast burning powders, and likewise for slow twist barrels and slow powder. What I have found is obtaining
the desired results from an overbore case design requires loading up with a slow burning powder, heavy bullets, and a fast twist barrel. The results are the longer the pressure pushes down those 26"-plus barrels, the more velocity is produced to send the heavy 22 caliber bullets downrange effectively. Another factor that becomes apparent is the need to scrub out that bore more frequently, sometimes as often as after 10 rounds. The high velocity produced in a small bore tends to copper foul quickly and degrade accuracy. A word of caution when working up loads is to always look for high pressure signs and stop shooting any load that produces such indicators.
Numerous cartridges fi t this cat-
egory, and I will touch on just a few. Some need extensive case preparation and forming, while others need only to be necked down. I consulted Quick-
This cartridge was developed by
Paul Middlestead of San Diego, Califor- nia. It is based on the standard 243 Win- chester case necked down to .224". The body dimensions remain unchanged but the shoulder angle is increased to 30 degrees, resulting in a longer neck (.300" vs. .241"). Case forming is accomplished by running a 243 case through a 22-243 full-length sizing die. Velocities have been reported to exceed 4,000 fps while keeping groups well under one-half MOA at 100 yards. This cartridge excels with heavier bullets in the 68- to 75-grain range with rifl ing twist rates of 1:9" or 1:8". Other versions include the 22-243, 22-243 Middlestead, and 22-243 A.I. 22 CHEETAH
The 22 CHeetah was developed
by Jim Carmichael, shooting editor of Outdoor Life magazine, and Fred Huntington of RCBS. The case is a full- length Remington 308 BR case with small primer pocket and necked down to .224". There actually are two versions of this case, the MK I with a 40-degree shoulder and the MK II with a 28-degree shoulder. This cartridge has proven to be superbly accurate and very effective out to 300 yards and more. 220 SWIFT A.I.
P.O. Ackley’s wildcat, blown out with a 40-degree shoulder. The three
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