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firing pin spring and its guide in position. This can result in the firing pin, and its associated parts, coming
out of the bolt while firing and causing a serious stoppage.
The likelihood of all of those problems occurring can be reduced by having a written checklist and
always having two people involved in assembling the weapon and using the checklist.
The gun is not invulnerable to knocks and bumps or even wear. Common problems demonstrated in
service were things ranging from something as simple as the cocking handle being rammed into a tree or
stone and bent or broken, to the receiver tube that holds the barrel and gas system in place cracking from
the strain of bi-pod use. Feed trays become worn and allow misfeeds and feed tray covers become bent
and restrict the movement of parts. Barrels and gas systems become overheated and can erode or warp
from exposure to high heat and pressure. The feed system can be damaged by an inexperienced user
attempting to forcefully close the feed tray cover while the bolt is forward. There is no support depot
repair facility for the Grantville M-60 and for that matter, no mail order parts houses or internet web sites
to provide replacement parts directly to the users.
Army technical manuals call for special lubricants, but in reality anything oily beats nothing and guns have
been operated on used motor oil or sewing machine oil or WD-40 (TM) more than once. For extended
firing, the synthetics do seem to work best as they do not evaporate as easily.
The gun depends on steel links to feed ammunition. Each link is stamped from steel, hardened, and given
a protective finish. A link firmly holds one cartridge in position for feeding by friction around the body of
the cartridge and what is essentially a flat spring that snaps into the extractor groove of the cartridge. The
link also has a piece that snaps over the next cartridge in between the front and rear of its link. Once links
become damaged by being flattened or bent or lose their metal temper or are heavily corroded, they are
of no use. Fortunately links that are recovered undamaged can be reused many times. Links are normally
deposited just below the link ejection port to the right of the gun, as they are not forcefully ejected. When
the gun is tilted to the left, links may be struck by the forcefully ejected fired cartridge cases and
scattered. For the purposes of Grantville, it may be best to make some sort of bag to catch both the used
links and ejected cartridge cases so they may be more easily recovered for re-use.
Ammunition is the most important factor for keeping Grantville's M-60 working and the gun's biggest
weak link.
The best ammunition for the M-60 is 7.62 NATO ammunition having the "NATO cross" on the case
head. How much of this is in Grantville? The ammunition for the gun should drive a 147 to 152 grain
bullet at 2800 +/- 40 feet per second from its barrel. As the weapon is gas operated, it is critical that the
correct amount of gas pressure be available at the gas port in the barrel to cycle the action for the next
round. Any factory loaded military round of 7.62 NATO ball or tracer ammunition that bears the cross in
a circle stamp should function the M-60 or any NATO standard weapon in that caliber.
Obviously it is possible to reload some ammunition. U.S. military 7.62 NATO ammunition can be
reloaded by sport shooters who reload .308 Winchester. This has led some to call for the seizure of all
.308 ammunition and components to feed the M-60. Besides the political problems this may cause, there
is a technical problem. Commercial .308 Winchester or hunting ammunition typically do not have
cartridge cases constructed to the same hardness as NATO standard. Firing some hunter's .308
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ammunition in the M-60 can cause stoppages and likely ruin the cartridge case for further reloading. The
commercial brass tends to be far softer than the NATO standard, resulting in bent and creased cartridges
on loading and more importantly, bent, torn, or broken rims upon extraction. Should the bend, tear, or
break be large enough, the cartridge will fail to extract and require a cleaning rod be run down the barrel
to extract the case.
Owners of military style semiautomatic rifles will also often note this problem. Some, like the FN FAL
type rifles that have a gas regulator, can be adjusted to slow their action speed and not damage brass as
much. But they are best served with ammunition intended for such rifles.
A problem for reloading the 7.62 NATO military ammunition that may be in private hands is that much
of it may be of foreign manufacture and have a Berdan primer rather than the U.S. standard Boxer large
rifle primer. Berdan primers are much harder to remove than Boxer designs and few Americans reload
them or have tools to do so. There are a number of ways to remove the Berdan primers, each much
more time and material consuming than the removal of Boxer primers.
Another problem facing reloading for the M-60 is the availability of usable primers. It may be several
years before new primers of any type can be reproduced. For the immediate future only the primers in
the hands of reloaders or already loaded in cartridges are available. A factor that comes into play when
loading for military weapons is the hardness of various primers. The firing pin strike of the M-60 is
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