Winchester M70 Trigger Adjustment


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Jaywalker
October 13, 2003, 10:10 AM
I found the following description of the way a gunsmith would adjust a Winchester M70 trigger and have a couple of questions:Adjusting the Model 70 Trigger
by Frank Kleinburg (fkleinbu@tivoli.tivoli.com)
(Original article posted at www.recguns.com)
Let me discuss how the trigger on the Model 70 works. Knowing how it works will allow you to know how a gunsmith would adjust it.
The trigger mechanism on the Winchester Model 70 is remarkably simple. Remove the barreled action of a Model 70 from its stock and you can see just how simple it is. You will see a trigger that pivots on a pin. Look at the rear portion of the trigger (normally hidden by the stock) and you will see a square head screw (the trigger stop screw), three nuts, and a spring (we'll call it
the trigger return spring).
The purpose of the trigger stop screw is to limit the amount of over travel of the trigger. It is possible to screw the trigger stop screw in far enough that you will not be able to pull the trigger enough to release the sear. Ideally the trigger stop screw should be screwed in as far as it can and still have enough trigger movement to reliably release the sear. This will allow for the greatest amount of adjustment of the trigger spring tension.
Tension on the trigger return spring determines a majority of the trigger pull weight (the rest of the trigger pull weight comes from the friction between the trigger and the sear). The spring surrounds the trigger stop screw, both can be seen just behind the trigger. The trigger stop screw is held in place by a pair of captive nuts, one on each side of the part of the trigger the stop screw passes through. A third nut sets the tension on the trigger spring. Tightening this third nut (turning it clockwise) against the trigger spring will increase the trigger pull. And turning it counter clockwise will decrease the trigger pull weight.
After making any adjustments, be absolutely sure to test for an excessively light trigger. To do this, screw the barreled action back in the stock. With the bolt cocked, in the closed position on an empty chamber, and the safety off, butt down the rifle. That is hold the rifle barrel pointing upward, let the butt bounce on the ground. It should take a considerable bump to cause the firing pin to drop (on the empty chamber).
On a friend's pre-64 Model 70 trigger, the spring had to be changed because enough of the trigger spring pretension could not be removed to get an acceptable trigger pull weight. Yet on another (on one of those new classic actions), it was possible to remove ALL of the trigger spring pretension. This is a dangerous situation because only the trigger to sear tension keeps the cocked rifle from firing.
Well I hope you now have a better understanding of how a Model 70 trigger works. Of course for all trigger pull weight adjustments you should take your rifle to a reputable gunsmith.


Of course, I plan to follow his advice and take the rifle to a gunsmith, but I was just wondering what else the 'smith might do. Would he, for instance, have to do anything other than "just pull hard" to get the action out of the stock and away from the melted stuff around the screw? Would he Loc-Tite Blue the screws when he was finished? Also, would he have to have special wrenches to fit the trigger screws?

Jaywalker

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Jim K
October 13, 2003, 09:37 PM
"Melted stuff around the screw"? Has the rifle been glass bedded? If so and it was done right, the action should still come out of the stock with little problem. If glass bedding is done wrong, you take the stock off with a hatchet.

On the trigger, just adjusting spring tension is usually enough to give a trigger pull that will satisfy most people. But in the "good old days" BAFL (before all the f*** lawyers) I also stoned the trigger engagement to give a pull of around 2.5 pounds, a figure that could not be reached by just changing the adjustments. This is tricky, though, and mostly not reversible. So if you, or your gunsmith, gets too happy with a stone, new parts may be needed.

Jim

Jaywalker
October 13, 2003, 10:24 PM
Thanks. I thought the M70 recoil lug had a factory-applied thermoplastic compound added as bedding support. Not so?

Jaywalker

Jaywalker
October 14, 2003, 10:55 AM
There was a little plastic/glass in the bedding, but not enough to interfere with removing the action from the stock. Special tools were not necessary, though you'd certainly need a narrow wrench if you wanted to move the two nuts separately. Otherwise, a moderate-sized adjustable wrench works okay. I could see no place that needed Loc-Tite.

I can see that anything further takes more knowledge, but a pull weight adjustment is simple. This M70 is now at a shade over four pounds and bumping the stock on the floor checks that it's safe. The trigger's much improved. It has no noticeable overtravel. There's a bit of creep that won't bother me hunting, and I can't see shooting a 300 Win Mag too often off of the bench, so maybe I'm done.

In the "For What It's Worth" category, there are three bolts securing the action and stock. When those bolts are removed, one notes that the one on the right is shorter than the other two. When reinstalling the short screw, one notes that it no longer reaches the threads in the action. One wonders about this for awhile, then one reverses the rifle and discovers that now all of the bolts reach their homes. ;)

Jaywalker

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