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Super GP100 tuning


Fishbreath

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I think this is appropriate to this topic. Ruger just sent this out yesterday. I do have to admit, I think the Super GP100's that I saw the IRC looked pretty dang sexy! One of the Team Hogue shooters was using one during the man-v-man shootoffs on Sunday and after some screaming fast strings remarked some to the effect, "Don't tell me that you can't run Rugers fast!":

 

Team Ruger Doubles Up on Divisional Wins at the 2021 International Revolver Championship

Congratulations to Team Ruger members James McGinty and Dave Olhasso on each taking home a divisional win at the 30th International Revolver Championship this past weekend. McGinty won the Limited division and third overall with a final time of 273.62 competing with his Ruger Custom Shop® Super GP100® Competition revolver chambered in 9mm Luger. Olhasso won the Limited Six division with a final time of 312.03 shooting his Ruger® GP100® six-inch revolver chambered in .357 Magnum/.38 Special.

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For all that it looks like mine is not reliable based on my post history, I've been enjoying it a great deal, especially now that it's running well. (Does take a bit of babying, though.)

 

Now I'm looking for a backup. Haven't seen any in stock anywhere, online or local, in a while.

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  • 3 weeks later...
On 8/19/2021 at 9:11 AM, Fishbreath said:

There's sometimes a wall at the start of the trigger pull, after the cylinder latch has started moving down but before the hand makes contact with the cylinder. That is, it isn't late initial timing.

 

I think I can close the book on this wall now, thanks to this cutaway view from the American Gunsmith Ruger DA sample on Youtube, and a forum post from a while back at one of the Ruger forums.

 

Here's my understanding of the problem, with my traditional tenuous grasp on terminology. When the hammer dog engages the top cam surface of the trigger (the top of the hook) at an angle, instead of straight on, the interaction between the cam and the hammer dog doesn't lift the hammer as far. (The hammer dog being diagonal means it's effectively less tall.) When that happens, the DA sear (the sharp angle on the bottom of the 'U'-shaped recess on the trigger) bumps into the front of the DA bearing surface (the curved notch on the bottom of the hammer), and has to push it up and out of the way.

 

The 95% solution was shimming the hammer dog more aggressively, so that it can't tilt as much. The remaining 5% solution was a few passes with a stone, followed by some polish, on the front of the DA bearing surface, where the DA sear would hit. For anyone else going down the same road, I wouldn't recommend any stoning of the bearing surface without shimming the hammer dog first. Thinking about the way the parts interact, it seems to me that reducing the bearing surface necessarily reduces the hammer arc in DA, which is of course to be avoided as much as possible.

 

The trigger is now as good as it's ever been: no hitching anywhere in the pull, and a very slight increase in weight toward the break as the mainspring compresses. It still pulls 7.5lb or so on the scale, but it's a much more pleasant 7.5lb, and I don't feel much need to chase a lighter pull right now.

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On 9/15/2021 at 5:46 PM, Fishbreath said:

 

 

Now I'm looking for a backup. Haven't seen any in stock anywhere, online or local, in a while.

 

I am 99% decided that my 929 won the comparison test, send me a pm if you want 9mm used.

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On 8/25/2021 at 8:25 AM, Dr. Phil said:

 

FWIW my 929 fired - actual rounds - in the 1st calendar year, 25,000. 2nd year, 22,000. 3rd 11,000. All pre- arthritis hiatus. Plus dry fire. (BTW the 929 is also not recommended for dry fire, and, will also break firing pins. 

 

Wondering if the redesigned TK Custom "unbreakable" firing pins, and changing the spring as preventative maintenance makes that issue disapear? If they fixed that and the weak arsed crane retaining set up, and factory repairs were fast and friendly like Ruger, I might become a fan boy instead of a fence rider.

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I broke several over the 3 year period. Different makes. Power Custom, TK and Apex. I broke very few stock pins, though the ignition system suffered from their length. It got so I was replacing FP springs every 1K - 2k. Often during a match - which seriously screws up the match rhythm thing. Tried sending the broken ones back as they are normally warranted. Pain in the neck keeping them straight!

I came across a gunsmith's question whether the reduced power FP springs were maybe to blame. Interesting.

I switched from reduced power to standard strength springs and changed them every 5K or so rounds and almost never broke one. Then I added a few (2 or 3) coils of another full power spring on the pin. Haven't broken one since.

Now I am wondering if the RP spring lacks the power to pull the FP back before the cylinder shears it off? (Generally the gun will still fire. But, the cylinder won't close until you push the broken tip back in. 🤣)

Few answers lead to more questions sometimes.

Right now it is run with a 1 1/4 spring and no dryfire.

But, I always did hate to dryfire LOL.

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9 minutes ago, Dr. Phil said:

I broke several over the 3 year period. Different makes. Power Custom, TK and Apex.

 

If memory serves the redesigned "unbreakable" TK custom pin did not come out until this year - have no idea if that will be a game changer but for now I am pretending like it is indeed unbreakable and on the rare occasions I am in the mood to dry fire just not worrying about it. 

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  • 6 months later...

Since I'm shooting a class this weekend, I figured I'd use the 'lots of rounds' test to see if I can go any lighter on hammer springs, now that I have primer seating depth sorted out, and hammers shimmed so that they pass the sharpie test for frame drag. In advance, I did some hammer fall measurements and labeled my springs, so I can work up from low to high.

 

I measured by hooking a trigger scale just under the hammer step and lifting, with the trigger pulled, until the hammer moved. The numbers don't seem comparable to Smiths, likely because of different hammer geometry and coil vs. leaf spring characteristics.

 

10# (Wolff): 2.25lb <-- starting point for testing, 7lb-ish DA pull. Lit 6 empty primed cases.

11# (flat wire or turned on a lathe, unknown provenance from previous owner): 2.5lb

11# (Wolff): just under 3lb

12# (Wolff): just over 3lb

12# (Wolff): 3.25lb <-- 100% reliability for about 3000-4000 rounds in 2022 to date, 9-10lb DA pull.

 

Will report back next week.

Edited by Fishbreath
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Findings!

 

The headline is that the extended firing pin is, as best I can discern, a backward step.

 

The 11# Wolff spring gave me two light strikes out of 400ish rounds on day 1 of the class, both at the end of the day as the gun dirtied up.

 

For day 2, I cleaned it and put in the extended firing pin (which is hand-fit to the gun). The same 11# Wolff spring gave me a light strike almost immediately, and I ended up having to go all the way to the heavier 12# spring before it was trustworthy again.

 

I'll be switching back to the stock firing pin, and trying the 11# spring again with some additional shimming to correct observed hammer drag. I'm still not sure what's different about the .357 gun that made it reliable with a 10# spring in 2020, but I guess I'm getting closer.

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Today's test had three prongs:

  • Asymmetric hammer shimming. The sharpie test showed that the hammer tilts slightly left, so I have 0.016" of shims on the left side of the hammer and 0.004" on the right. Subsequent sharpie tests show a little tiny bit of drag on the right side with this setup, but it takes several dozen trigger pulls before the sharpie starts to wear off against a cylinder or two with a symmetric setup.
  • The stock firing pin. It's not fully clear to me why the stock part is better, but experimentally, it absolutely is. While we're talking about firing pin springs, the screw-in-bushing GP100s use the same firing pin spring as the LCR, which makes it a little easier to find parts. This spring is identical in outside dimensions, but has 0.014" wire against the Ruger part's 0.015", so it's a good reduced power firing pin spring option.
  • An 11# Wolff hammer spring, with a measured hammer fall weight of 2.75lb.

It was fully reliable for 200 rounds, minus one that was clearly a faulty primer (it didn't go off after three single-action strikes). I plan to shoot once or twice more before Nationals to more fully verify function, but I think the hammer shimming and stock firing pin make a big difference.

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  • 2 weeks later...

I'm back down to the 10# hammer spring (~2.25lb hammer fall weight) after yesterday's testing—only about 100 rounds, though; the match tomorrow will give me some additional data.

 

The most important thing for reducing hammer spring weight is fully eliminating hammer drag. The GP100 hammer is much freer to move side to side in the frame than Smith hammers, so ensuring that it strikes the transfer bar without any losses elsewhere in the system is key.

 

Depending on the particulars of gun and parts, that may require asymmetric shimming: as I said above, I have 0.004" on the right side of the hammer and 0.016" on the left side, because the hammer tilts very slightly to the left when fully down. To eliminate any residual indication of hammer drag, I got my diamond files out and made an inward cant on the sides of the hammer: it's slightly narrower now at the front than at the back, so it fits more freely into the slot in the frame. It gets an A+ grade on the sharpie test now; I can pull the trigger as many times as I like, and sharpie marks on the sides of the hammer show no indication whatsoever of frame contact.

 

The second most important thing is reducing the hammer step. In my experience, with the ideal reduction, you'll see an impact mark on both the hammer step, where it contacts the frame, and the hammer face, where it contacts the transfer bar. If you pull the trigger, then watch the hammer while resetting the trigger slowly, the hammer shouldn't move as the transfer bar retracts, or should move at most to a barely perceptible degree. If it moves so much so that it's easily visible, you're putting extra stress on the transfer bar and firing pin return spring.

 

I also did the same trigger hitching fix I mentioned in my 10/7/21 post from the .357 gun, but some further reflection suggests that might be the wrong approach. The Ruger DA trigger pull is extremely sensitive to the length and rotation of the hammer dog. Filing down the hammer step allows the hammer to rotate slightly further forward, which means the hammer dog is also rotated forward further in its at-rest position. It may be better to solve the hitch by taking a little bit off of the back upper surface of the hammer dog, which controls how far out of the hammer the hammer dog spring/plunger can push the hammer dog.

 

I have some Ruger DA revolver gunsmithing resources on the way, which will hopefully help to give me a better understanding of what the various dimensions on the hammer dog do, and what can be adjusted to solve trigger pull problems.

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Quick reviews of two Ruger gunsmithing resources:

 

American Gunsmithing Institute Ruger Double Action Revolver DVD

2.5/5 stars. The good: the host knows revolvers generally, and it has some good video of a cutaway gun cycling. Seeing the interaction between the hammer and trigger parts during DA really clarifies what's going on inside the gun, and helped me reason about it based on what I feel.

 

The bad: it's only an hour and a half of video, and doesn't cover much in the way of adjustments/repairs in detail. The host didn't bother to have a Ruger parts diagram handy to call things by their actual names.

 

The Ruger Double-Action Revolvers: A Shop Manual (Kuhnhausen)

4.5/5 stars. It may be a manual for the Security/Police/Speed-Sixes rather than the later-model GP100s/SP101s/Super Redhawks, but in terms of mechanism and function, the two families are almost identical, so most of it applies. It's 174 pages of densely-set diagrams and procedures, covering both inspection and repair. Much of the repair stuff is beyond me, the home tinkerer, but lots of the trigger information is well within reach for someone with a good set of fine stones or diamond files, and an equally good amount of patience.

 

I am vindicated in my light filing of the secondary DA bearing surface on the hammer; that's one of the suggested fixes for hammer hits, where the DA sear on the trigger impacts the bearing surface early.

 

It probably deserves 5 stars as a reference manual for working on the Six series, but I ding it half a star using it as a GP100 resource: the hammer dog is one of the parts that's slightly different, and the GP100 dog has a compound shape where the Six series seems to have a simpler one. Hammer dog problems and symptoms line up (too short a hammer dog can cause stacking in the middle of the pull, or a wall near the start; too long a hammer dog can cause reset issues where the dog won't fully reset over the DA cam on the trigger), but there may be some nuance to adjusting a dog on a GP100, which is why I ordered three from Numrich to play with.

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One trick I've heard in a few places about diagnosing GP100 triggers is to put a temporary spacer on the hammer dog, to make it effectively a little longer.

 

I tried that tonight: I cut a tiny piece of paper out of a handy notepad, folded it up so that it would fit behind the top of the hammer dog, between it and the hammer, and pushed it into place with the tip of a knife. Wouldn't you know it, it solves all the problems at once: no hint of a hitch when the DA sear joins the party, and no reset problems. That's good guidance for fitting the next one, and a caution for anyone working on a Super GP: do as little as possible to the hammer dog, because removing any material is going to cause problems.

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Well, after the best hand filing I've ever done on anything, to say nothing of critical action parts in a gun where 0.01" is a massive change, time for a dive into the inner workings of the Super GP100 again.

 

The hammer dog fit controls two potential trigger problems: an early hitch or wall, and late stiffness/clicking.

 

PXL-20220603-214310197.jpg

 

The early hitch/wall occurs here, before the pawl reaches the ratchet and begins to turn the cylinder. It's caused by too short a hammer dog. With a short hammer dog, you may also encounter a hitch that occurs when you leave light to moderate finger pressure on the trigger, after it fully resets and you start to pull again.

 

It's possible to lengthen a hammer dog, by gently hitting it with a hammer and more or less cold-forging it longer, but Numrich appears to have access to factory-new hammer dogs, so it's possible to dispense with that. The Ruger mavens suggest lengthening the tip, but as I'll get into later, controlling tip length doesn't appear to be how Ruger fits the part at the factory.

 

Mechanically, the binding here happens when the DA sear (the right-angled bottom surface of the C-shaped trigger hook) hits the underside of the hammer, because the hammer dog, being too short, hasn't lifted the hammer far enough out of the way. You can also fix this issue by lightly stoning the underside of the hammer, where the DA sear rides. However, knowing what I do now, I don't recommend that: reducing that surface reduces the DA hammer arc, and you want as much hammer swing as possible.

 

Anyway, moving on.

 

PXL-20220603-214326292.jpg

 

The late hitch/bind occurs here, near the end of the cylinder rotation. It's easiest to feel if you pull the trigger enough to unlock the cylinder, turn it by hand to the next spot, and continue the trigger pull. It manifested as a click for me on all three of my spare, non-fitted factory hammer dogs. This is caused by the hammer dog being too long.

 

The Kuhnhausen shop manual for the Six-series revolvers says it may also appear as stiffness at the end of the trigger pull for very slightly over-length hammer dogs, or hammer dogs with incorrectly-shaped tips. The shape of the hammer dog/trigger cam and DA bearing surface/DA sear changed between the Six series and the GP100 family, so I can't confirm whether that's still the case on the later-model guns.

 

Mechanically, I believe this happens because the hammer dog lifts the hammer too far before releasing it to the DA sear, so the trigger jumps a bit to catch up to the hammer.

 

Let's take a look at the hammer dog now.

 

PXL-20220603-213707644.jpg

 

In this orientation, the hammer goes to the right of the hammer dog, facing left, with the top of the hammer toward the top of the picture. The indicated surface on the top of the hammer dog rests against the inside of the slot in the hammer, and controls the angle at which the hammer dog protrudes from the hammer. The more material there, the earlier it bottoms out in the slot, and the less the hammer dog protrudes.

 

The marked bottom surface is where old-school Ruger gunsmiths suggest working, but I think it's better left alone, based on the following evidence.

 

PXL-20220603-204145637.jpg

 

This is the hammer dog from my 9mm Super GP, fit by the factory to the gun. It is sitting on top of a new, unfit hammer dog. The only obvious difference in profile is at the arrow. It's the same with my .357 factory-fit hammer dog. By controlling the angle of the hammer dog, you control its length relative to the trigger surfaces. So, in my admittedly limited experience, the surface indicated by the arrow is the only one you should adjust—stick to polish everywhere else.

 

The process I recommend is this:

 

If your hammer dog is slightly short, try hammer dog shims. (Lance Shively sells them, and you'll probably need some of his shims to get the hammer-to-frame fit right anyway.) Eliminating hammer dog tilt may bring you back into spec.

 

Otherwise, buy a few from Numrich, and fit them to the gun. As far as I can tell, you want to change the angle of the indicated surface while removing as little as possible from its bottom corner. Here are two reference photos.

 

PXL-20220603-213707644.jpg

 

The hammer dog on the left is the factory-fit one in my 9mm gun, which had slightly too much protrusion (too much material removed). The one on the right is a new, unfitted part. You want something in between.

 

PXL-20220603-212612623.jpg

The factory-fit part is on the left. The part I hand-fit is on the right. The difference between good and bad is extremely subtle, so work carefully and check often. I did most of the material removal with a 400-grit diamond file, checking frequently, then switched to a 600-grit diamond file once I got close. This surface doesn't need to be polished—it doesn't slide against other metal pieces, merely serves as a stop for the hammer dog.

 

I don't recommend anything more than polish on the bearing surfaces, the two bottom facets of the hammer dog by the words 'bad fit' and 'good fit'. Even very fine-grit stones or sandpaper can remove enough to cause trouble, based on the saga of this gun. I put a little dot of Flitz on a patch, put the patch on my bench, and rubbed the dog on the patch until the surfaces felt smooth. Putting sharpie on the tip and working the trigger a few times suggests that both of the bottom facets on the hammer dog are implicated in the DA trigger pull: the long one on the right side of the hammer dog (facing back into the hammer, slanted up and to the right in this photo), and the short one on the left side of the hammer (facing forward into the gun, slanted up and to the left).

 

The end result is a near-perfect pull—I ding it for a bit of stacking at the end, but not enough for me to notice even at casual group-shooting pace.

 

Hopefully this is helpful to someone else down the line, looking to better understand the Ruger trigger.

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A bit more work done tonight. In my parts bin, I have an old Super Redhawk hammer, which I bobbed and tried for a while on the .357 gun. I thought it gave me better ignition then, but it also had a terrible gag at the beginning of the trigger pull... which I now know how to solve. I didn't even have to file on the spare hammer dog; it fit right out of the box.

 

I did two additional things to this hammer tonight: one because it predates Ruger's move to the LCR-style screw-in bushing in the full-size guns, and one to combat hammer drag.

 

The first task involved removing some material from the hammer step. Newer Ruger hammers have a step about 1/8" tall; old ones have a step about 1/4" tall. The larger old-style step hits the firing pin bushing on the newer guns, and the repeated impacts can cause the bushing to back out over time. Very slightly reducing the lower 1/8" of the hammer step means it won't hit the frame/bushing anymore.

 

PXL-20220611-015203097-2.jpg

 

For reducing hammer drag, I've found that shims are about a 90% solution, and the other 10% can be solved by taking a bit of material off the sides of the hammer toward the front, tapering it like this.

 

PXL-20220611-015320574-LI.jpg

It doesn't take much at all: the taper above is substantially exaggerated. This is about as far back as you have to go:

 

PXL-20220611-015256061-2.jpg

 

This hammer was .407" wide, and is now about .380" wide at the front edge where the file cut the deepest. I'm still missing a little bit: not the circular scratches 2/3 of the way down (those are leftovers from the original shaping), but the tiny discoloration at the right edge of the highlight, between the taper and the rest of the hammer. I think that's probably not enough to matter.

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  • 3 weeks later...

You can lighten the hammer somewhat... BUT you need true carbide end mills AND cutting oil AND extremely low cutting speed.. I have a HF mini mill ( I call the "Destroyer")... It's still a work in progress. That SS is some tuff stuff!!  EDM would remove more metal versus what can be removed by milling holes but most machinist's aren't going to mess with so small a project?... I bought 2 hammers and am not satisfied with the 1st. one... Yes, I will put up pics when I get better.... Now to find a REVOLVER!!!

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Edited by mikeAZ
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18 hours ago, mikeAZ said:

BUT you need true carbide end mills

 

Or, in my case, an angle grinder to take the spur off, a carbide Dremel bit for additional shaping, and a file I don't mind wearing out for finish work.

 

I sure wish I had a mill, though! I'd love to try skeletonizing a hammer.

 

 

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Pics added... BIG difference in carbide mill quality...  I have the shims, spare dogs, 1 ea. extra hammer (Supposed to be the correct ones)... I was supposed to have the Factory 9mm by now BUT< BUT, "she" is a no show as of 6/27/22. I'm told that the 357's were more popular, I may have to take what I can find (At this point, NADA). 

 

JAY, Looks like you have the game pretty well figured out, keep it going! Mike

Edited by mikeAZ
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