ISSC Mk 22 Screw Replacements- Best to do the updates before firing the rifle
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Quoted from GammaRT from this thread.
http://thefiringline.com/forums/show....php?p=4906817
ISSC MK22 Socket Head Cap Screws
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Hi all, this is in response to the socket head cap screw fix by weneary3.
First of all, thank you for a very informative explanation & guide to address the screw loose issue experienced by many others in various online discussions.
Back in December 2011, in anticipation of the arrival of my new MK22 around Christmas, I took the advice of weneary3 and acquired some stainless steel 6-32 x 3/4 and 6-32 x 1/2 socket head cap screws. I wanted to replace the factory screws as a "preventive maintenance" before using the rifle. BTW, my local Home Depot and another big box hardware store did not carry this type of screws. My local RC model hobby store and two industrial supply stores (Fastenal & Brafasco) do have these screws. However, Fastenal only sell them in packs of 50. I got free screws from Brafasco as I was purchasing the blue Loctite from them.
When my rifle finally arrived, I proceeded to do the swap as well as Loctite all the other screws. To my surprise when I removed the factory vertical & horizontal cap screws: they are not the same size as the 6-32! Now, the 6-32's will screw into the factory screw holes but the fit was very sloppy. Visual inspection shows the 6-32 looks skinnier than the factory screws. So a thorough investigation was in order.
Being a rifle from Europe intended for an international market not exclusive to the U.S.A., I thought it was a bit odd that the fasteners (screws) would be in imperial sizes (e.g. 6-32). A quick check of the hex (Allen) key confirms my suspicion: the factory screws use a 3mm hex key. This translates to a M4x0.7 metric size cap screw. Measurement of the major diameter of the thread confirms the M4x0.7 metric size.
I proceeded to replace both the vertical & horizontal screws as well as the stock plate cap screw (the one that fasten the stock plate to #39). I found the factory stock plate cap screw too short. The screw hole in #39 was tapped much deeper than the factory screw was using.
So here's the revised screw replacement info for non-stripped threads:
Vertical screw: stainless steel socket head cap screw M4x0.7x18mm
Horizontal screw: stainless steel socket head cap screw M4x0.7x16mm*
Butt Stock Plate screw: black oxide or stainless steel socket head cap screw M4x0.7x12mm
*I am using a longer screw than factory. The factory horizontal screw sits flushed with the far side of the nut when tightened. A longer screw with 15mm or 16mm length will protrude a few millimeters beyond the nut - a much better fit mechanically. And there is room for these longer screws.
Hope this help.
Cheers... happy plinking!
_______________________________________________________
(right idea but wrong thread sizes)
Easy and cheap fix. So far for my MK22 all goes well with an additional 400 rounds with no further issues.
After much aggravation and frustration only added to by ISSC ignoring my requests, I was able to figure out the cause and correct the issue with the "vertical" bolt being stripped out causing all the FTE's (failure to eject) This bolt threads into piece #39. The cycling of the bolt will loosen and then strip the threads out of piece #39.
The bolts are show on the left side of the picture.
The original bolt is a #6-32 allen cap bolt and about 3/8" long which was only engaging about 1/3 of the threads. When either of these two bolts loosed, you will get FTE's. Wish I knew why they used short bolts which were so short?....
For non-stripped threads- purchase a 2-pack of #6-32 x 3/4" long allen cap head screws in stainless steel for less than a dollar. For the "horizontal" screw use a #6-32 1/'2" long screw.
FOR THREADS ALREADY STRIPPED- (My vertical screw had already stripped out) I retapped it to #8-32.
WORKS PERFECT NOW!
_____________________________________________________________________________
There is also that firing out of battery (or even out of chamber) issue. That is a design issue. A semi auto should not be able to fire unless the bolt is either right forward or close to it.
[youtube]4IlxUsAZueg[/youtube]
--------------------------------------------------------------------------------
Quoted from GammaRT from this thread.
http://thefiringline.com/forums/show....php?p=4906817
ISSC MK22 Socket Head Cap Screws
--------------------------------------------------------------------------------
Hi all, this is in response to the socket head cap screw fix by weneary3.
First of all, thank you for a very informative explanation & guide to address the screw loose issue experienced by many others in various online discussions.
Back in December 2011, in anticipation of the arrival of my new MK22 around Christmas, I took the advice of weneary3 and acquired some stainless steel 6-32 x 3/4 and 6-32 x 1/2 socket head cap screws. I wanted to replace the factory screws as a "preventive maintenance" before using the rifle. BTW, my local Home Depot and another big box hardware store did not carry this type of screws. My local RC model hobby store and two industrial supply stores (Fastenal & Brafasco) do have these screws. However, Fastenal only sell them in packs of 50. I got free screws from Brafasco as I was purchasing the blue Loctite from them.
When my rifle finally arrived, I proceeded to do the swap as well as Loctite all the other screws. To my surprise when I removed the factory vertical & horizontal cap screws: they are not the same size as the 6-32! Now, the 6-32's will screw into the factory screw holes but the fit was very sloppy. Visual inspection shows the 6-32 looks skinnier than the factory screws. So a thorough investigation was in order.
Being a rifle from Europe intended for an international market not exclusive to the U.S.A., I thought it was a bit odd that the fasteners (screws) would be in imperial sizes (e.g. 6-32). A quick check of the hex (Allen) key confirms my suspicion: the factory screws use a 3mm hex key. This translates to a M4x0.7 metric size cap screw. Measurement of the major diameter of the thread confirms the M4x0.7 metric size.
I proceeded to replace both the vertical & horizontal screws as well as the stock plate cap screw (the one that fasten the stock plate to #39). I found the factory stock plate cap screw too short. The screw hole in #39 was tapped much deeper than the factory screw was using.
So here's the revised screw replacement info for non-stripped threads:
Vertical screw: stainless steel socket head cap screw M4x0.7x18mm
Horizontal screw: stainless steel socket head cap screw M4x0.7x16mm*
Butt Stock Plate screw: black oxide or stainless steel socket head cap screw M4x0.7x12mm
*I am using a longer screw than factory. The factory horizontal screw sits flushed with the far side of the nut when tightened. A longer screw with 15mm or 16mm length will protrude a few millimeters beyond the nut - a much better fit mechanically. And there is room for these longer screws.
Hope this help.
Cheers... happy plinking!
_______________________________________________________
(right idea but wrong thread sizes)
Easy and cheap fix. So far for my MK22 all goes well with an additional 400 rounds with no further issues.
After much aggravation and frustration only added to by ISSC ignoring my requests, I was able to figure out the cause and correct the issue with the "vertical" bolt being stripped out causing all the FTE's (failure to eject) This bolt threads into piece #39. The cycling of the bolt will loosen and then strip the threads out of piece #39.
The bolts are show on the left side of the picture.
The original bolt is a #6-32 allen cap bolt and about 3/8" long which was only engaging about 1/3 of the threads. When either of these two bolts loosed, you will get FTE's. Wish I knew why they used short bolts which were so short?....
For non-stripped threads- purchase a 2-pack of #6-32 x 3/4" long allen cap head screws in stainless steel for less than a dollar. For the "horizontal" screw use a #6-32 1/'2" long screw.
FOR THREADS ALREADY STRIPPED- (My vertical screw had already stripped out) I retapped it to #8-32.
WORKS PERFECT NOW!
_____________________________________________________________________________
There is also that firing out of battery (or even out of chamber) issue. That is a design issue. A semi auto should not be able to fire unless the bolt is either right forward or close to it.
[youtube]4IlxUsAZueg[/youtube]
