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GP100 & SP101 improved but...

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Old May 1st, 2017, 10:19 AM   #1
Join Date: Jan 2011
Location: Vancouver, Wa.
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GP100 & SP101 improved but...

My health has kept me away from hobbies and activities for the last couple years. I am feeling marginally better and getting around to things.
Over the last couple weekends I have "worked up" my wife's SP101 and my GP100 (both 3" in .357 and older well broken-in models bought used).
I have:
-followed the IBOK instructions
-installed hammer, trigger, and hammer dog shims (end shake is within spec).
-installed Wolff springs (details below).
-bobbed hammer and removed single action sear on GP100.
-De-sharpened and polished both triggers.

Good before... awesome now! Nice and smooth, easy to stage, predictable release. I went back to the factory Trigger Return Spring. The 10# worked fine but I like the trigger to "push" my finger out of the way. For the Hammer Spring the 9# has worked with all/several brands of primer I have tried. Still may put the 10# in just because.
My problem with this one is HAMMER RUB, at the top - left portion of the hammer. It is properly shimmed. There is barely room for the hammer to clear the frame but...the hammer pushes hard to the left side? I am not sure the hammer is true and flat on the sides, seems to be though? However, the top of the hammer was askew (fixed). Before the action work and shims it rubbed on both sides.
I have also found the Hammer Strut to be bent. I got it nearly straight. Ruger is sending me a new one, shows up today.
What to do? It pushes to the left and/or... the sides of the hammer are not true on the axis and or... the frame opening is not symmetrical and/or...?

Hideously painful Double Action before..."OK" now.
Initially put in 10# Hammer and 8# Trigger Return Springs. This felt decent enough but the trigger return was soft and slow. So I put the factory Trigger Return Spring back in.
Fires reliably with 9# Hammer Spring, really do not want to go heavier unless i can lighten up the Trigger Return Spring.
Now Double Action is REALLY HEAVY again, but smooth.
I have done all the recommended deburring, smoothing, polishing, etc... listed in the IBOK.
Will the 10# Trigger Return Spring that came with my GP100 Kit fit the SP101?
I would like to try to go with 10# and 10# for both springs.
This also has a little Hammer Rub on both sides, but barely, I think I can fix it.

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Old May 1st, 2017, 11:27 AM   #2
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Oh, almost forgot... added XS Standard Dot Sights to both revolvers. What a huge improvement!
After installing them I was admiring them and noticed the one on the GP100 was very dim compared to the one on the SP101. I called XS (bought from them directly because of special nature of GP Sight) and they had a new one at my door three days later. No charge and no need to send in the first one. That is GREAT CUSTOMER SERVICE FROM XS SIGHTS!
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Old May 1st, 2017, 12:43 PM   #3
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Something that affects the trigger return on the GP and SP actions is the Trigger Plunger (KH03200) and its action on the Cylinder Latch (KH04504). The bevel on the Trigger Plunger tip should be mirror burnished, as should the mating surface on the Cyl Latch. You may also need to mirror burnish the sides of the Trigger Plunger.

My GP100 has the reduced hammer and trigger return springs, along with a complete internal polishing, and it functions perfectly. I don't use hammer or trigger shims, as I don't desire to fool with repositioning them when reassembling the gun after a field or detail strip.

With a friend's SP101, I had to go back to the stock trigger return spring for reliable trigger return, despite intense polishing of all the related trigger group parts and the spring 'tunnel' in the trigger guard unit.
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Old May 1st, 2017, 01:37 PM   #4
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Thanks firescout, I did get all those areas, thoroughly. I can only think something is hanging up on the return somewhere? Pawl, transfer bar, or ...? I did polish and smooth these areas as well. When I get a chance I should take it apart and look for signs of rough wear. Maybe polish the faces of the Transfer Bar?
It does appear to be on the return, specifically. It does not catch or stop, just soft. It is smooth when pulling and pretty decent with the 8# Trigger Return Spring. Just really soft and slow on the return. It is still smooth with the factory Trigger Return Spring, and returns fast, but a very heavy trigger pull. My wife does not like it much.
What is the factory Trigger Return Spring weight? I thought it was 11#, but I keep seeing 10#? Maybe my Wolff 10# is a moot point?
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Old May 1st, 2017, 05:58 PM   #5
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The trigger return weight (stock) on the SP is 10 lbs and GP I think is now 10 but used to be 12 lbs. Someone claimed a while back that Ruger changed the trigger return spring weight down to 10. As to the scuffing on the hammer sides what does the inside of the frame look like? Brownells used to make an India stone that was square to smooth out the inside of the frame to get rid of burrs. As to the hammer dragging on the one side if the new hammer pivot pin does not solve the problem I wonder if the hole in the hammer for the pivot pin is a true 90 degrees to the side?

The springs are interchangeable between the SP and GP. Don't know why the action is now heavy on the SP. I have the 9 lb mainspring and 8 lb trigger return in both my GP and SP and the SP double action is about 8.4 lbs and the GP 7.5 lbs, the difference due to better mechanical advantage in the GP.

Last edited by Rover; May 1st, 2017 at 06:02 PM.
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Old May 1st, 2017, 08:01 PM   #6
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Rover, for the GP100, actually it is the Hammer Strut that showed up today. I will take a close look at the existing Pivot Pin, tomorrow. The inside of the frame in this area looks fine as I have smoothed it up, conservatively. It did not alleviate the rubbing though. I stopped there because I did not want to start "hogging out" the frame without a clear understanding of the cause. Initially, before the action job and shims, the hammer was sloppy loose in the frame and rubbed all over on both sides. Now it PUSHES or LEANS to the left. I may try truing up the sides of the hammer and thinning it MINUTELY to use thicker shims and get more clearance on both sides of the hammer. It is very close on both sides.
I cannot imaging I bent the hammer removing the spur. We used a milling machine and let the cutting do the work, very slow, very careful. I cannot imagine bending the hammer, period.

Since the factory Trigger Return Spring on the SP101 is 10#, that answers that question.
The SP101 did not just become heavier. Before I worked on it, it was heavier and rough. Now with the factory Trigger Return Spring it is still fairly heavy, but better, and really smooth. With the 8# Trigger Return Spring and 10# Hammer Spring it is pretty decent. That return is just so soft.
The area of the trigger guard where the plunger meets the trigger strut is about the only place that I cannot figure out how to smooth up, with the tools I have on hand (no Dremel). How to describe... front of Trigger Return Spring Channel where the Plunger stops and the Trigger Strut has the little groove it rides in. I will see if I can smooth it up?
Also maybe assemble with Transfer Bar out and see... then Pawl... one at a time?
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Old May 8th, 2017, 03:08 AM   #7
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Update (if anybody cares?)...

I figured out the SP101. I found a slight burr at the top right hand edge, right at the end, of the trigger return spring plunger shaft. This made the plunger hesitate ever so slightly before going completely forward and resetting the trigger plunger.
With the factory Return Spring it easily pushed by. The 8#... not so much.
I had already deburred and polished the shaft but this area was just far forward enough to be missed by the 1/4" bit.
I knocked the burr off the shoulder with a round needle file and polished the area with a Green Polishing Compound covered Q-Tip and a drill (still do not own a Dremmel).
Nice and smooth reset with the 8# Trigger Return Spring now. I prefer the 10#, but it is my wife's gun and she likes it this way.

I have not had time to look further into my GP100 hammer rub issue other than:
- hammer pivot pin is straight and true.
- the new hammer strut made no difference.
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Old May 13th, 2017, 08:02 AM   #8
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Well, just for the sake of closure...

I figured it the hammer rub issue with my GP100.
I used calipers, a lapping plate, and permanent marker to determine that the hammer is in fact true and square.
Then I used calipers and a known small - flat - straight edge to confirm that the left side of the opening on the frame for the hammer was NOT true and straight.
The area around the axis point for the hammer pivot pin was .010" - .012" wider than the area around the top and bottom of the hammer.
So I slowly and carefully with many measurements removed material from the frame at the top and bottom.
Now the axis point is only .004" - .005" wider than the top and bottom.

At this point, other than possibly bead blasting the exterior some day, I consider these projects done.
- reamed cylinder throats
- chamfered forcing cones
- complete action jobs
- shims on: hammers, hammer dogs, and triggers
- contour and high polish triggers
- XS standard dot sights
- 8# TRS & 9# HS on SP101
- 10# TRS & 10 HS on GP100
- bobbed and DAO conversion on GP100

I did all work myself, for the first time. With a LOT of help from: IBOK, 4D Reamers, Trigger Shims, XS Sights, the good people here at rugerforum, and a very good friend with a milling machine.

I have added a few pics just because.
We call my wife's SP101 her "Pimp Gun" on account of the faux pearl inserts.
Also included is the XS sight I used as this is a question that comes up often on the forums.
Attached Images
File Type: jpg 20170513_082225_1494689861360.jpg (3.45 MB, 10 views)
File Type: jpg 20170513_082157_1494689879906.jpg (3.76 MB, 13 views)
File Type: jpg 20170513_082138_1494689895027.jpg (2.95 MB, 11 views)
File Type: jpg 14946900779751059663942_1494690103254.jpg (3.55 MB, 15 views)
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