How does a two stage trigger get it's method of operation? (what I'm trying to say is I know what it feels like but how does it do that)

Is it possible by machining/modification to change a two stage trigger into a single stage trigger?

1894--

Good question---

The two stage on most military rifles work by creating two different levels of leverage. The first stage pull the sear down easily because the point of leverage on the trigger is closer to the fulcrum point. (where the trigger and sear are pinned together). When the rear hump of the trigger reaches the bottom of the tang the point of contact is roughly twice as far from the fulcrum point and so the trigger pull is doubled for the last half of the pull.

It used to be common to silver solder an extension on the front stop surface of the trigger with a set screw that bore against the sear body. The set screw took up the first stage and left the second stage for the primary trigger. That meant there was half as much sear engagement as before but roughly double what an over-ride trigger has, so plenty safe on a hunting rifle.

Some old English express rifles were done differently. They cut off the first stage trigger hump and then cut the top of the sear down until there was only the primary trigger engagement left. Some have a small extension added to the *rear* of the trigger for an overtravel adjustment.

1894,

In the cold or while wearing glove, 2 stage triggers provided an easy way to "feel" the trigger, so you would know when the sear was ready to trip. The first stage of a 2 stage design is meant to "take up" the slack and usually was the result of the trigger pivoting on a "hump" built into the sear. The last stage or second stage, is the actual force required to trip the sear. Or something like that.

Yes it is possible to turn a 2 stage into a single stage. What it would take to convert it would depend on which trigger it is you have.

Malm

May I borrow your thread for a moment...

Regarding using a two stage trigger with it's built-in safety features, what can you do to smooth the second stage and lighten it so that a little extra "bump" fires it, like a well-adjusted single stage? I'm talking of Mauser 98 and P-17 / Mod 17 Enfield triggers.

Thanks,
Todd

BTW has anyone seen the new 'mil-spec' single stage replacement triggers from Brownells? Pretty pricey, but I like the idea. How about someone setting up a service to weld up your 98 trigger and re-machine to single stage, wherein you send them yours in exchange, and they send you one they have already done up. For say $20 - $30. Any of our manufacturing members interested?

Todd--

I dusted off this old post and re-posted it. I think it covers what you ask, but I have a clarification if you want it.

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Since the sear is pivoted, it rotates. Which has to mean there is only one position that the sear is 90 degrees to the bore line. Where is it?

The accumulated slop of the cocking piece in the shroud which is screwed to the bolt which is slightly sloppy in the rear ring ALL adds to the amount off of 90 degrees the cocking piece is held by the sear.
Cock your rifle and look at it in profile. The cocking piece is not straight with the bore is it? How far “off” is it? We’ll need that later.

The sear moves about .060 in the first stage and .030 or so in the second stage. Figure an arc of .090 and a radius of 1.350 on the 1912 Steyr I keep next to the computer. Now the distance above the pivot point where the top of the sear is located has to be calculated by taking measurements. I use the bottom of the rear tang as an index point.

On this ‘98 the center of sear pivot is .030 below the surface of the rear tang. The tang is .115 thick from the bottom to the bottom of the cocking piece slot and the sear sticks up .104 into the slot.

That means the top of the sear is .249 above the pivot. .250 is a quarter inch and so we’ll round to that.

Now you tell me. Is the surface of your sear square with the bore line at rest….or in the fired position?

If yours is like mine its about 3 degrees, 10 minutes off square at rest. Its leaning forward by that amount.

Using the formula for calculating subtension of tangent angles. Says something profound like: “The angle between a tangent and a chord drawn from the point of tangency equals one-half the angle at the center subtended by the chord.

I cheated…. I rotated the sear on the table of the optical comparitor until the top of the sear had rotated downward by .900 (10x mag) and re-measured the angles. Bingo! 90 degrees when its in the fired position.

Now, how much slop has the cocking piece got in it when cocked? How far off 90 degrees is it?
Is the angle of the cocking piece equal 90 degrees to the bore line to begin with in the actual part? Yes on this M98.

So how much off 90 degrees should the cocking piece or sear be ground to allow a perfect flat and 90 degrees to the bore line fit between the two parts?

My head hurts! You do that part.
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Geometry determines trigger pull. If you can correctly calculate how to attaing a flush, flat, and perfectly mated sear/cocking piece a good trigger pull will follow.

Ive tried two methods to turn them into a single stage. The first was to simply grind out the hump that makes the first stage. Suffice to say the two stage is better IMHO. The other I find to be much better, simply build up the bottom of the reciever a bit where the trigger cam contacts it but not too much. I used silver solder, have fired a couple hundred rounds and it has done well so far. Another member has done this with JB weld. Perhaps Jack or Malm could suggest a better means of build up. This essentially takes away the second stage, and since the first stage pull has more leverage than the second, you can obtain a lighter pull by removing the second.

Dont forget to "rough play" test your trigger work for saftey after adjusting. If you build it up just enough to make the sear disengage just at the end of the first stage, there is still a lot of sear engaging the cocking piece to assure a safe sound trigger.