inch / metric differences
no problem AGG...had the pictures hosted already so just a matter of sifting through them.
to continue telling about these fine rifles, here are some more pics that help illustrate
*basic* differences between the "metric" and "inch / commonwealth" patterns, largely
copy/pasted from a previous post elsewhere:
there are alot of differences. many subtle, others not so much.
most any parts kit and receiver can be assembled regardless of their respective
origin / pattern (metric/inch)
as far as wether the receiver is inch or metric, it could be either or some of both if
we're discussing century stuff. i'm not sure about the receivers they made, but some of
the (metric) Imbel receivers they imported, while type 3 externally, had some of the inch
cuts done to them. the pertinent areas to check (besides external profile) are:
the cut for the mag (inch on left):
corresponding portion of mags (again, inch on left)
because the cut out is larger on inch guns, they MAY function w/ either pattern mag but
sometimes the metrics will be sloppy and can cause feeding problems. (in-spec) metric
receivers won't accept inch mags.
here is the difference in floorplates, inch on right:
Commonwealth rifles have a folding rather than fixed knob on the charging handle:
here are the cuts for the charging handle (inch on left, cut back to allow for the folding handle):
the folding inch version may be employed on an unmodified metric receiver if the folding knob is
ground enough to fold over the forward end of the receiver. the slide portion is also a bit thicker/
wider than the metric and needs to be filed / sanded to fit into the CH rails.
inch top covers have downward-protruding tabs at their rear which fit into recesses in the
receiver. metric covers / receivers do not feature this.
inch cover on left:
inch cover on rightt:
cuts for the tabs at the rear of the inch top cover:
a comparative metric photo without the cuts....(my T1 SA58 which is metric type 1 but has
some inch sand cuts inside[dished-out portions along the carrier guide rails]):
sand cut features rarely encountered on metrics are the norm for the Commonwealth rifles'
receivers (as DSA pic above shows) bolts & (most obviously) bolt carriers. as seen here:
bolts are different too between them (metric on left now):
differences at rear of bolts / carriers, inch in front:
inch to left has a relief cut
firing pins do not interchange.
inch pattern rifles have a BHO which holds the bolt back only when YOU push it up while
retracting the handle, not automatically on the last shot as the metric rifles do. you can
replace the short pin on these (5/64"DIA IIRC) or the whole unit if you desire the last round hold-open.
the inch BHO shaft (and it's recess in the receiver) is slightly larger in diameter.
consequently a metric version will fit a little loose but should function ok.
inch on left:
-note the metric BHO has a 'wide foot'. there are also (earlier) metrics with a narrow foot,
and the Izzy variant which has a hole drilled through the tab that extends up off the foot.
no pic sorry...
the Commonwealth mag release is much different than the metric, extending the control surface
out to the rifle's left. interchangeable to metric receivers with the (longer) inch screw to
clockwise from top left are inch, metric, Israeli (my fav by far) & a tapco "Holland":
inch pattern flashiders employ a notched barrel / pin&donut arrangement whereas most metric
muzzle devices just screw on (excepting a few lugged variants).
the Commonwealth pattern features an "open-eared" gas block (a few metric variants feature this,
too, but i believe use metric-style regulator assy's.) that accepts a different type of front sight,
a blade more than a post as on metrics. the Commonwealth line of sight is ~3mm higher than the metric,
and employs a folding rear aperture not found on the metric pattern.
here are inch and metric gas blocks (inch on left)
the gas regulator / adjusting nut on the L1A1 aren't threaded onto the gas block as are the metric.
L1A1 on left:
gas plugs, "A" auto setting, note inch is not lettered but has a groove on the auto side which (or the A)
must be oriented to the rifle's top when you're not launching grenades or you'll be single shot!
inch on left:
"G" grenade setting, inch on left:
front & rear views, inch on left:
among the differences you don't readily see are the washers employed in timing the Commonwealth barrel:
and the 45* gas port as opposed to metric @90* to the bore's axis.
the lowers, while interchangeable amongst upper receiver types as assemblies, have major differences
which preclude interchanging many internal components. a quick way to check for lower type is the metric
pistol grip is fixed from it's underside by a nut while the Commonwealth PG is fixed by a bolt down thru
the top of the lower. buttstocks are quite different. Commonwealth lower has tangs that accept the buttstock:
on a metric rifle the stock or it's ferrule butt up against the lower. (can be seen in the next pic....)
the Commonwealth selector is way oversized compared to a metric version also. here are selectors
alot yet to cover, but there's a start!