Five, 10, 15, and 25-round magazines are available from PRI, with either regular
USGI-type floor-plates, or wide 6.8 SPC floor-plates.
Powder selection for maximum velocity is more difficult than .223 or .308
because the 6.8 SPC has less case volume compared to its bore area. Hodgdon
H322 and Alliant Reloder 10X produced the best combination of accuracy and
velocity in my barrel with the V-MAX bullet. Other notable powder choices
include Vihtavuori N130 and N133, AA 2230 and Winchester 748. Any large rifle
primers will work in the Remington and SSA brass. Sub-minute accuracy was easy
to achieve with neither elaborate brass preparation nor a lot of load
"tweaking". In short, it is a forgiving cartridge.
While 6.8 SPC can be chambered in almost any 7.62x39mm or 5.56 rifle, or
Contender pistols, the most compelling platform is the AR-15 because of the
SPC's heritage. An AR-15 chambered for 6.8 SPC requires only a new barrel, a
new bolt cut to accept the larger case head diameter and new magazines.
Standard complete AR-15 lowers require no modifications, and 6.8 SPC uppers are
built on standard stripped upper receivers.
Just after 6.8 SPC's announcement, rumors flew that USGI M16 magazines would
feed 6.8 SPC with little or no modification. This unfortunately turned out to
Shown here fitted with a lightweight titanium JET sound suppressor, the 18-inch
6.8 SPC rifle provides all the capability of the SPR, but superior terminal
performance.
be false. After five or six 6.8 SPC cartridges are loaded into a USGI magazine,
they begin to bind up; after seven or eight, the magazine walls will bow out
wider than the receiver's magazine well will allow.
Precision Reflex Inc (PRI) solved the problem by designing a magazine
specifically for the new cartridge. Their magazines have narrower ribs than
USGI magazines to accept the larger body diameter of 6.8 SPC cases, while
keeping the same external dimensions for weapon compatibility. The PRI design
uses steel thinner than the aluminum used for USGI magazines and flat-ground
welds to join the two halves in manufacture, instead of the overlapping spot
welds found in USGI magazines. As a result, the maximum possible cartridge
over-all length (COAL) is increased to about 2.310 inches from about 2.245
inches in USGI magazines. A 6.8 SPC magazine of about the same dimensions as
the 30-round USGI magazine holds 25 rounds, while a smaller version holds 15.
PRI offers five and ten-round magazines to satisfy some local legal
requirements. C Products LLC has just developed a 6.8 SPC magazine, which
should ship April 2006.
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