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Ambidextrous M37 safety mod

PostPosted: Sun Oct 29, 2017 10:21 am
by impala59
I have been using my extended capacity M37 in IPSC type competitions and have on a few occasions fallen foul of having the safety catch in the wrong position, causing embarrassment and time loss. As these courses of fire can involve strong and weak side shooting, and, where the briefing states that safety catches are to be used it is easy to become confused in the heat of the moment. That said, I decided to investigate making an ambidextrous safety catch that would be fool (me) proof :lol: (My original doodle complete with spelling mistakes and also the modification for version 2 below)
ASP (7).JPG (125 KiB) Viewed 916 times

I decided to use brass as it is relatively easy to work, and hard enough for non-pressure areas. I had a 1" piece of 1/4" round rod and some 2mm plate. I tried 6mm rod but that was too loose in the trigger plate hole. (1/4" = 6.35mm) I cut a 2mm slot parallel at each end of the rod and centrally filed a 2mm slot at 45 degrees to the end slots. I interference fitted the 2mm lever blanks to the slots then drilled and tapped for M3 screws.
I removed the trigger plate from the gun and stripped it down so as to remove the original safety catch. I re-assembled the trigger plate without the safety catch as my modification could be retro-fitted.
I fitted the lever blank to the left side of the new safety catch shaft and tried for fit and function. All seemed well so I refitted with the original detent spring and plunger in place and marked the detent positions for safe and fire. I then drilled a shallow hollow at each stop point and slightly dressed with a round needle file the furrow that the detent pin would track in. Next, I roughly profiled the lever shapes then fitted for full functionality test. With one slight bug, everything was fine and worked as I wished. The bug was the assembly allen screw head which protruded into the comfort area of the trigger finger on either side, it just felt wrong. Hence the modification to my drawing, and, when I get some more 1/4" rod the mark 2 which will see the levers mounted high on the shaft (in the FIRE position) and retained by a countersunk screw from the top. This will, I am sure redress the 'felt' problem without changing the function. In the SAFE (down) position the trigger is locked as effectively as with the standard safety catch. This safety catch feels normal (forward to fire) and will, I hope, eliminate the odd occasions where shoulder changes have caused confusion, as the trigger finger when placed on either side and moved into a ready position, finds the safety catch which positively alerts the shooter to its condition. Whilst I need some more 1/4" brass rod, for my mark 2 version, ultimately I will probably make it from steel, although I believe that it could be fabricated from other materials such as aluminium or nylon.
One thing that has been said about the 37 is that it's fully ambidextrous (apart from the safety catch which has to be changed to accommodate lefties or righties, Mine is now properly ambi! Another thing that occurred to me while putting it together, is that the levers could be any shape or size (within reason) so that oversized items could be used for gloved hands etc.
Photographs showing the various positions, (also my file marks etc as this is only a working prototype) I hope you find it of some interest
ASP (1).JPG (154.67 KiB) Viewed 916 times

ASP (4).JPG (126.55 KiB) Viewed 916 times

Re: Ambidextrous M37 safety mod

PostPosted: Sun Oct 29, 2017 10:24 am
by impala59
Continued due to 3 picture limit
ASP (2).JPG (116.35 KiB) Viewed 915 times

ASP (3).JPG (122.5 KiB) Viewed 915 times

As work progresses, I will update

Re: Ambidextrous M37 safety mod

PostPosted: Tue Nov 07, 2017 9:36 am
by impala59
With a new supply of Brass rod I got busy and threw together the Mk 2 rotating ambidextrous safety and a push thru' ambidextrous safety, I have to work fast as the ideas spring up, and I'm not so good at documentation (although I suppose I document them on the forum so there is some record, plus, hopefully further ideas from other members) First the rotating version
the components;
ascmk2 (2).JPG
ascmk2 (2).JPG (90.01 KiB) Viewed 879 times

Assembled with sharp edges removed
ascmk2a (1).JPG
ascmk2a (1).JPG (55.18 KiB) Viewed 879 times

The underside showing 'fire' slot
ascmk2a (2).JPG
ascmk2a (2).JPG (63.75 KiB) Viewed 879 times


Re: Ambidextrous M37 safety mod

PostPosted: Tue Nov 07, 2017 9:46 am
by impala59
The right side in 'SAFE' position, as can be seen this version is much more compact
ascmk2a (3).JPG
ascmk2a (3).JPG (65.9 KiB) Viewed 879 times

The right side in the 'FIRE' position (forward for Fire seems logical to me) the lever is now out of the way when firing and does not interfere with the trigger finger.
ascmk2a (4).JPG
ascmk2a (4).JPG (61.82 KiB) Viewed 879 times

The detent pin (original) sits on the flat upper surface and positively holds the catch in the fire position, when safe the catch also is held positively, but a smooth transition is easily made with the trigger finger on either side, in either direction I shall use this on my next competition and if all is well I shall fabricate in steel

Re: Ambidextrous M37 safety mod

PostPosted: Tue Nov 07, 2017 10:10 am
by impala59
Whilst awaiting the materials for the above, another idea popped into my head, that of a push thru' ambidextrous safety. Many of these ideas come from taking my guns down to component level so as to understand the workings and machinations of the design. I started by silver soldering a 2mm bar into my 1/4" rod to get an oversize blank
ptasc (3).JPG
ptasc (3).JPG (78.27 KiB) Viewed 879 times

I then cut a 'W' shape, where the 'V' either side is for the left and right 'FIRE' slots and the raised centre is the 'SAFE' position. I measured the distance between the 3 positions and the location of the original spring detent and filed corresponding slots. With a little fitting, the catch is positive in all positions and snicks into place solidly. As the piece is marginally longer than a standard catch, I angled the faces to keep them out of the way. I may reduce the size after some field testing, but for now this, like the rotating catch above seems to work well and will be re-fabricated in steel.
ptasc (8).JPG
ptasc (8).JPG (88.32 KiB) Viewed 879 times

As can be seen, the catch is a touch long, here in the 'SAFE' or 'central' position, but as soon as it is pushed in either direction for 'FIRE', it is no longer an issue, and does not snag the trigger finger on either side
ptasc (9).JPG
ptasc (9).JPG (71.97 KiB) Viewed 879 times

Once again I hope this has been of some interest to you