RUGER MarkI/II/III Pre-travel screw install - DIY project

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RUGER MarkI/II/III Pre-travel screw install - DIY project

Post by Bullseye » Wed Aug 17, 2005 3:21 am

For RUGER, Mark I/II/III pistols
Trigger pre-travel screw installation – DIY Project
By Bullseye

There isn’t really much to this project. This procedure can be performed on either an aftermarket or factory trigger. You just need to get a 4-40 thread pitch, 3/16" long Stainless Steel Allen set screw from your local hardware store. Next drill & tap the trigger mid way between the pin through hole and the bottom of the trigger's front face. (see picture)

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I tapped mine for a 60% thread size, which was using a #42 twist drill (or 3/32" drill bit) to drill the pilot hole. A size #43 twist drill bit can also be used for this installation and it will provide a 75% thread size. But, the #43 twist drill will require extreme caution when tapping, as this very small sized tap is prone to breaking and a #43 sized hole puts a lot more stress on it while tapping the threads. Do not attempt to cut the threads too deeply (in one pass) with this tap or it will certainly break it. It's best to use a drill press and vice for drilling this pilot hole, but it can also be done very carefully with a hand drill. The hole needs to be very straight. The trick is to not drill it too deep into the trigger body or drill into the hole opening for the trigger cross pin. You can use a smaller drill bit for drilling a pilot hole and then gradually step-up to a 3/32" sized bit.

The Allen (Pre-travel) screw can be adjusted to take most of the slack out of the trigger before it engages the sear. This addition will shorten the travel of the stock Mark II's trigger pull considerably. You will need a little bit of slack (only a very little) to leave enough room for the gun’s disconnector to reset during any sustained fire operations. The trigger will not operate repeatedly if this slight amount of slack is not there and the disconnector fails to reset.

The pre-travel screw can be a pain to adjust because you'll have to completely remove the trigger each time to adjust it. However, once you get it adjusted correctly, the feel is worth the wait. I used a little blue Locktite to keep the screw from moving under the gun's recoil. This adjustment screw uses the trigger slot face as the primary surface for the adjustment and will keep the trigger from returning all the way back to the forward most position.

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If you have a stock Ruger target trigger (A01201) with an Allen Screw in the top most part of it (above the trigger pin through hole) this screw is for "over travel" adjustment, not "pre-travel."

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A pre-travel screw can be added to this type of factory trigger, as has been done to the trigger in the picture.

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On a (A01200) old stock factory Mark I or Standard trigger. (See picture, upper most trigger) Some of you may have to file off the lower bump (make it flat) located in this position by the factory. Then drill and tap the spot where the former bump was for your set screw. You may have the insert come out when you drill and tap this bump. That's because that bump is actually a pin inserted by the factory into the Mark I trigger. No big deal, but you will have to now use a bigger set screw. The good news is: you won't have to drill another hole because the new screw size I'm going to give you will fit right into it. The bad news is: now it's a metric sized set screw; 4mmx5mm, .70mm pitch. You'll now need a metric 4mm .70mm pitch tap. And, a #2 metric Allen Wrench. The rest of the installation follows the regular procedure.


Also 6-32 x 3/16 inch size Allen set screw may also be used for this installation procedure if the preferred 4-40x3/16 (Stainless Steel) size is not available at your local hardware store. Centering the hole for drilling with a 6-32 screw is a little more critical as not to drill into the trigger pivot pin through hole. Use the applicable sized twist drill bits for installing the 6-32 screw from the Tap Chart for the size threads you desire (Again I recommend using the 60% thread size).

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Good luck.

R,
Bullseye
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