The
recoil spring should be changed, at the latest, when it has lost 0.500”
of free length from new. At this point, the spring has suffered a
considerable reduction in load exerted at installed (when the gun is in
battery).
How long will an ISMI recoil spring last? In
independent testing, ISMI spring have endured in excess of 100,000
compression cycles. We don’t recommend going that long between changes
however. With an ISMI spring, practice routine maintenance and change it
once a year. See our warranty information on page 5.
Should I use a spring buffer? We do not recommend
the use of a spring buffer in the 1911 pistol. Buffers tend to be a
bandage for a recoil spring that no longer performs adequately. Put a
fresh spring in instead. Buffers reduce slide travel which can have an
adverse effect of feeding reliability. In addition, buffers can break
apart during firing and make the gun inoperable.
STI & SVI magazines and springs - how can I get
them to function reliably? There are a number of things that are
involved in attaining reliable magazine function. Proper magazine
dimensions are critical. ISMI includes the factory specifications on
each package of STI/SVI magazine springs. If your magazine is out of
spec, you can return it to the factory or have an experienced
pistolsmith tune it. Make sure that the interior surface of the feed
lips are smooth and free from burrs. Virgil Tripp at Tripp Research has
conducted independent spring testing (see www.trippresearch.com) and
covers his results in the tech talk section of his web page. They also
provide a number of tips and recommendations for STI/SVI mag bodies.
ISMI standard capacity mag springs have 11 coils
instead of the standard 10 coils. We did this to maximize spring loading
with the belief that it is easier for the shooter to remove a coil if
necessary rather than try to add another coil to the spring. In some
cases this will cause the solid height of the spring to be too long thus
causing the top 3 transition coils to be compressed inside the spring,
leading to premature failure. If in doubt as to whether you should
remove a coil, give us a call.
The amount of space that the spring works in when
fully compressed is directly dependent on the internal dimensions of the
magazine. We have customers that can use our 170mm spring in their 140mm
mags with no loss of capacity; conversely we have had customers tell us
that in what should be the same magazines, that they have lost a round
of capacity with our 140mm length springs. This is the cause and effect
of differences in the internal side to side dimensions of each magazine
body.
