WA SVI Trigger tuning

WA SVI Trigger tuningby
Matthew Dean (aka MobiusStrip)
written Friday, May 17, 2002


NOTE:
All part no’s refer to the WA SV manual.

The following parts need to be separated from the rest of
the Frame

  • Trigger Bow # 27 and pad
  • Leaf Spring # 72
  • Hammer Strut # 38 (with hammer
    attached)
  • Beavertail # 30
  • Valve plate connector # 36

Trigger Bow
# 27
The outside edge is normally quite smooth,
but the inside is often rough with a burred edge. Lightly
break the rough edge with 800 grade abrasive paper.
Now the trigger should be fitted into the grip frame.You will
notice that with the trigger unit in the grip, that there
is some sideways slop, this will be felt as “creep”
when the trigger is pulled, and it is even more noticeable
when the pull is lighter.

To cure this firstly measure from
the back of the trigger bow to the back face of the trigger
pad (approximately 44.5mm). What ever the measurement is –
write it down!

Now, a very small amount at a time, you have to slightly bend
the trigger bow side arms (from the inside), and put it back
in the gun, until there is practically no sideways movement
of the trigger bow in the grip frame, but it must still be
able to slide freely.

Once you have accomplished this,
measure the distance from the back of the trigger bow to the
back face of the trigger pad again. The distance will most
probably have changed, if it has, it needs to be brought back
to the original length, or the trigger over travel screw #
79 will not function correctly.This is done by bending the
front (trigger attached) and rear straps so that you regain
the length you originally had. It is tricky to do this and
the finished item should slide in and out of the trigger slot
without binding or slopping from side to side.

Leaf
Spring # 72
This will have rough edges on each
of the individual tabs, use 800/1000 grade abrasive paper
to break these edges so that they are nice and smooth.

For a lighter pull, bend back the
sear tab – 2, and trigger return tab – 1, slightly. How much?
It is very hard to specify the exact amount and of course,
individual preference, but if you go too far you can end up
with other problems such as trigger bounce, where the hammer
falls to half cock as the slide slams forward or a situation
where the Hammer has slack at rest.

Hammer Strut
# 38
Separation is optional, but provides the
best results. Once separated from the hammer, this part too,
should be de-burred, especially in the lower part where it
rides inside the mainspring housing # 31. In fact on some
of the custom hammer struts you see for the “real thing”,
the lower part of the hammer strut is cylindrical!

When finished reassemble to hammer
for the next step.

Hammer
# 29
This part has undergone modification,
as can be seen by the photo, a new section of reinforcement
webbing now runs up the front of the hammer, where as the
old style has reinforcement only at the bottom. My experience
is that the new style can have a problem with the Half Cock
Notch lip catching on the inside of the frame.

To see if your gun has this problem,
assemble the gun but leave out the Sear # 24 and the Disconnector
(bottom half) # 25, Sear Pin # 24 and Beavertail # 30. Now
rock the Hammer gently back and forth and feel for a slight
catching as the Hammer moves through its arc of travel. If
it does, chances are this is the Half Cock Notch Lip hitting
the frame, as shown on the photo. Use some sort of marker
pen/water-soluble paint to lighten/darken (dependent on original
colour) this edge, then after a few Hammer rocks, remove the
Hammer and look to see if the pen mark/paint has been scraped
off. If it has, a gentle “kiss” with a fine file
on this area should be enough to solve this. – Do not go too
far only a small amount of material should need to be removed.

Beavertail
# 30
Modification
to this part is partly optional, an area that can cause problems
is for this part to be only partially depressed when gripping
the gun, and thus not unblocking the trigger bows path, leading
to a locked trigger. Gripping the gun tightly is the obvious
way to avoid this, but people with small hands (like me) are
especially susceptible to this, and the lack of “meat”
on our hands makes this sometimes hard to do.It might only
happen occasionally, but usually in the middle of a shootout!

Increase the tolerance for error by removing material from
the underside of the part of the Beavertail that protrudes
furthest into the gun. Before modification this part measures
at 4.75 to 4.5mm, (there is a slight taper). After removing
material it measures 4.55 to 4.0mm. A small change but a significant
one, and it has helped myself and others who find that this
has given them trouble.


Valve
plate connector # 36
Once
removed from the frame, this part again has rough edges to it,
by now the phrase, “break the edges with 800/1000 grade abrasive”
paper should be springing to mind.

Post Assembly Tuning Time
to set the Trigger over travel screw, # 79. With the magazine
out of the gun, hold the trigger back and ease the hammer back
and forth, and slowly screw in the over travel screw a bit at
a time until a “bump” is felt, this means you are hitting
the half cock notch and the over travel screw then needs to be
backed out. Continuing to hold the trigger back and ease the hammer
back and forth, keep backing out the screw until the bump is no
longer felt, then back out another half turn and lock in place.

Now strip the gun, and reassemble, minus the Beavertail. Now looking
at the left side of the gun, in the exposed are where you can
see the Hammer Strut, Leaf Spring and Trigger Bow, once again,
hold the trigger back and rock the hammer back and forth. What
you are looking for is unwanted contact between the Sear tab of
the Leaf spring and the Hammer Strut. If there is contact, the
Sear tab will have to be bent so that it clears but still operates
as intended. See Leaf Spring diagram for slight change in shape
of tab 2.

Also look for scratch marks on the inside of the
Beavertail where the Hammer strut may have rubbed. If it has rubbed,
and the Hammer Strut is already de-burred, (see above), relieve
the inside of the Beavertail where there are rub marks with a
half round needle file, then blacken up with a marker pen, reassemble,
hold back trigger and move Hammer back and forth. Disassemble
and check for marks. Repeat this process until no contact is made.

Make sure the gun is lightly lubricated with a good quality oil,
in all the internal moving areas.


Last
updated:
Tuesday, February 11, 2003 9:53 PM

Except where listed, all contents are Copyright 2003 ArniesAirsoft




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