Double action characteristics - M15 S&W

[SPR1]

I picked up a new in box 20 year old M15 (S&W Heritage series with Turnbull color case hardened frame). The double action pretty much sucked out of the box.... Yes, I am a heathen and I am shooting it..... When I took the factory grips off to wipe it down I discovered some light rust. That helped me rationalize shooting it.

I slicked up a few burrs inside, put a 14 pound rebound spring and a different factory mainspring in it. This work has dramatically improved the trigger pull. As has firing and dry firing it about a thousand times.

But, since new, the final stacking portion of the pull, where you could stage it, is much more of a creepy, hard, increase in pull than any other Smith I have had. I am wondering if this could be insufficient clearance between the DA sear nose and the trigger?

Thoughts?

 

[armorer951]

To answer your question, if I understand your terminology correctly, no. More than likely insuffecient gauge between the top end (contact portion) of the hand and the ratchet, as the gun carrys up.

 

[SPR1]

By gage, do you mean length, i.e. The hand needs to be longer?

 

[SPR1]

Ps. I just double checked, the cylinder is rotated and locked tightly before the problem is felt. It is the last bit of carrying the hammer back where the creep is felt.

 

[armorer951]

It's actually a width issue. The "creep" you describe is most likely the hand making it's way past the ratchet after the cylinder has locked into battery. This condition will be mitigated somewhat by firing/use.
Since other issues can cause the creep you are describing, proceed with caution. It's impossible to properly diagnose using only your description of the problem. Best to have it checked out by a competant, S&W trained revolver armorer, or factory personnel.

 

[SPR1]

Thank you.

 

[tomcatt51]

It's actually a width issue.

Width issue kinda. The hand is thicker than the width of the opening it has to squeeze thru after the cylinder has locked. The usual fix is a thinner hand. It's easy to thin the hand. Only the tip needs to be thinned and only on the center pin side.

 

[Bullet Bob]

If it's any consolation, I have two of those, and neither has the double-action pulls I am used to on K frames.

 

[SPR1]

Width issue kinda. The hand is thicker than the width of the opening it has to squeeze thru after the cylinder has locked. The usual fix is a thinner hand. It's easy to thin the hand. Only the tip needs to be thinned and only on the center pin side.

That sounds simple enough to fix. Thx

 

[tomcatt51]

That sounds simple enough to fix. Thx

It really is, with qualifications. Check the stacking (that's what the glitch at the end of the pull seems to be called) on each chamber. It will usually vary some as the ratchet fitting is rarely perfect. You thin the hand hand so the chamber(s) with the least stacking have none. That will leave the others with varying amounts. To fix that you have to even out the ratchets. Thats another story.

The part of the hand you thin is the part you see poking thru the recoil shield if you open the cylinder, hold the clinder release back, pull the trigger and hold it back. You remove material from the cylinder center pin side. Use a stone. Go slowly .002" can be a bunch. Do it with the hand removed from the gun. Stone a little, test, repeat as necessary. A 0-1 verniered mic is a good thing to have.

S&W std hands seem to have a thickness range of ~.005". If you know somebody who has accumulated a bunch of them you go thru them with a mic and find a couple thinner than yours to try.

 

[SPR1]

Much appreciated

 

[scooter123]

Check for wear marks inside the frame recess and sideplate. My 620 had this and a 0.0015 hardened shim on the side of the trigger producing the rub smoothed it out perfectly. As for the cause, I suspect the pivot hole in the trigger might be just a hair off perpendicular.

 

[SPR1]

Thanks. Will do

 

[tomcatt51]

On the forged triggers you also want to check the cross pins, make sure none are protruding and dragging.

 

[SPR1]

I recall seeing some drag marks on the side of the hand. Me thinks there may be some burrs in the slot. Surgery is scheduled for Saturday morning.......