Adventures in the Ruger GP100

[Bazoo]

Well, I've been wanting a GP100 for a few years and I finally got one. It was made in 1993. It appears to have been unaltered and not abused.

I first learned how to disassemble it. I made a Ruger popper out of a piece of short cleaning rod and bought a special bit from brownells to remove the extractor.

I carefully polished some of the internals, most notably the hammer strut and the trigger return spring channel. Nice and smooth, think I'll leave the factory springs. I changed the white outline rear sight and bought a black front sight to have the option over the red insert.

I've been working on some loads, with a borrowed RCBS 38-150-SWC. I have purchased my own and will continue both 38 and 357 load development. I also have a Lee 358-140-SWC that I'm working with.

I'll see about getting some pics in a few days.

Thanks for listening.

Bazoo

[megasupermagnum]

Don't be scared to try weaker trigger springs. Unless you are Jerry Miculek and can outrun a trigger, the 8# trigger return spring is a no brainer. And while the 9# hammer spring usually works, I've not heard of the 10# spring not working with all primers. I just finished my new GP100. It came with an average double action trigger, 4# single action with some creep. I followed Iowegian's guide, put in trigger shims, and used the 8# return and 9# hammer springs. So far 100% reliable. The best part is I have a buttery smooth 7 1/2 pound double action pull, and crisp 2 1/2 pound single action pull. My other GP100 has a 10# hammer spring, yet over time the trigger smoothed out such that the double action is similar, and the single action is a super crisp 2 1/4 pounds. The GP100's can have phenominal triggers, as good or better as any S&W I've ever witnessed.

You would be shorting yourself if you didn't try the 175gr Keith bullet and 10 grains of Bluedot. I've not found a 357 magnum this didn't shoot great in.

[Bazoo]

Thanks for the reply MSM. I'm reluctant to change the springs because I like a little heavier single action pull than most. 4 pounds but crisp is right where I want to be. I don't have a pull gauge but I'm pretty close, knowing that my 1911 is 5 pounds. That said I may change the trigger return spring to 10 pounds to see how I like it.

I plan to shim the trigger at some point but not the hammer, for ease of disassembly. I'm not a member over on Ruger forums but I have seen a lot of Iowegans posts.

Are you talking about the Lyman 358429? I don't have one but currently. Are they too long for the GP cylinder in magnum brass (seated to the crimp groove) in your experience? I just got some bluedot to experiment with, so I'll be trying it in both 357 and 44 special / magnum.

[megasupermagnum]

Yes, the 358429 or clones. I use the NOE 360-176-SWC, as I like to play with hollow points. If I only wanted solids, I would go for the Arsenal molds version. They fit crimped in the crimp groove no problem. I load to 1.645" OAL The GP100 could handle up to about 1.660" or so, but I like to leave a little wiggle room. As far as I know, the only gun they wont fit in is the S&W 27, although I'm sure there are a couple other short ones.

[megasupermagnum]

What really helps is the hammer dog shims. The hammer dog usually has a ton of play. It cleaned up a notchy DA feel in mine, which was likely the transition from hammer dog to DA sear. Both my GP100's had tight frame to hammer fit, and I doubt shimming there did any real good. I seem to remember my shims on both being .002", one on each side. It makes me happy that my hammer doesn't rub is about it.

One nice thing about leaving the heavier springs, they almost seem to cover up any grittiness.

[Bazoo]

Preciate the advice. I might give the lighter springs a try sometime but I am fairly content with the trigger pulls.

I think I'd like to chamfer the charge holes. Got to learn about it though as I'm not familiar with what's required or any disadvantages.

I am still looking for a holster to get me by until I can make one to suit me.

[dannyd]

Have fun with it I have 5 started in 1989.

[tward]

Great gun! I’ve had one since 1993 and have not found a load that won’t work well. I did change the springs and put fiber optic sight on it, way better for old eyes. I’ve loaded everything from round balls to 200gr. And they all shot well. Round balls are fun and quiet, think civil war 36 cal. Tim

[contender1]

Kudos on getting a fine handgun. I'm a LONG time Ruger collector & shooter. I was totally happy with my Security Series DA Rugers & didn't have a "need" for a GP-100.
Then,, I handled a Match Champion. I had to have one. Then a regular GP became available for a very fair price. It moved in. Soon after,, another GP with a longer barrel did the same thing. Next,, along came the MC in 10mm. Oops,, now I own several GP's! :D

Most guns benefit from a good, careful action cleaning,, and sometimes spring changes. A smooth action is what most prefer,, and a clean crisp trigger is what works best. And,, it can actually be heavier than you think,, if the action is done right. (I have one gun,, that most swear it has a 1-2 lb pull,, but it will measure 3.5 lbs all day long.) Shims do assist in reducing drag & helping keep things smooth.
Too light of hammer springs can result in misfires.
Iowegan has some excellent info,, and on the original Ruger Forum,,, there are also some very knowledgeable folks. The original Ruger Forum,, (the .com one) has internet server issues,, and you can't join,, but a member over there also frequents here, is a top notch Ruger DA gentleman. RoninPa is his handle over there. I can't recall if it's the same here.
But if you need anything I can put you in touch with him. He's a gunsmith, and a FFL.

You mentioned chamfering the charge holes,, and I can attest to the FACT that our own DougGuy can & will do this. I had him do a S&W 646 for me for competition. You can bet it'll be right,,, AND his prices are very fair.

[Bazoo]

I appreciate the replies. I had thought about Doug. I want to learn it myself though if I'm able. The wife's 686 could use it too.

I'm still young and poor. I have less than 10 firearms, but the ones I have I enjoy and master. Shooting the wife's 686 is okay, but I'm glad to have my own. My GP grips help reduce recoil a lot compared to the wife's open backstrap and wood grips.

[dannyd]

I appreciate the replies. I had thought about Doug. I want to learn it myself though if I'm able. The wife's 686 could use it too.

I'm still young and poor. I have less than 10 firearms, but the ones I have I enjoy and master. Shooting the wife's 686 is okay, but I'm glad to have my own. My GP grips help reduce recoil a lot compared to the wife's open backstrap and wood grips.

Load some light loads and enjoy the gp.

[Petrol & Powder]

I really like the GP-100. Strong, accurate, strong, reliable, did I mention they are strong :D

They do respond very well to some judicious polishing and shims. Like the OP, I avoid shimming the hammer to make disassembly/re-assembly easier.

To maintain a crisp and rapid trigger reset, I sometimes leave the factory trigger spring in place. A slightly lighter hammer spring is a useful modification, particularly after polishing/shimming the action. Ruger uses some seriously heavy springs and you can safely drop the weight of the hammer spring by a few pounds without affecting reliability. There are some drawbacks to reducing the hammer spring weight by too much; at some point reliability will suffer and lock time will increase as the hammer spring gets lighter.
The GP-100 can be a very accurate gun. The GP-100/S&W L-frame debate has been going on since the introduction of the GP-100. I think the GP-100 is every bit the equal of the S&W L-frame and the GP may be a bit stronger due to its solid frame (no side plate) and locking crane. However, that's sort of like saying a 100lb anvil is stronger than a 98lb anvil.

Ruger introduced the GP-100 a few years after the S&W L-frames but I think they really hit a home run with that design.
S&W discontinued the fixed sighted L-frames (581 & 681) but the adjustable sighted 686 lives on.
You can still get a new GP-100 with fixed sights in 3" barrels and 4" barrels (in the Match Champion line).

Congratulations on obtaining a fantastic DA revolver.

[onelight]

Good job Bazoo !
I have had a Gp100 a few months now and it is very easy to shoot well.
I hope you enjoy it.

[Bazoo]

Thanks all. I have already made both specials and magnums to test. So far I'm getting 2.5"-3" groups rested at 25 yards, but I'm working on cutting that in half. Not sure if it's me just needing to familiarize myself more with the gun or something with my loads.

[Xringshooter]

Thanks all. I have already made both specials and magnums to test. So far I'm getting 2.5"-3" groups rested at 25 yards, but I'm working on cutting that in half. Not sure if it's me just needing to familiarize myself more with the gun or something with my loads.

I will tell you with some confidence, the more you shoot the GP the better it will get and so will you. Loads do have a lot to do with it but being completely familiar with your firearm really helps.

Member "Contender1" (post #9) referenced me from the RugerForum.com (thank you Ty). I use a different name here, picked up when I was shooting PPC many moons ago. I actually built a PPC competition revolver from a GP100 in 1992 and got heckled a lot from long time PPC shooters - until I let them shoot my revolver. Then their tune changed. Most PPC guns at that time were mainly made from Model 10 S&W's, no one (but me I guess) really considered using something else. I replaced the 6" barrel with a bull barrel and adjustable (4 positions) sight rib. I went with a (at that time) Bullseye brand 6lb trigger return spring and a 9lb hammer spring for the lightest trigger pull and reliable ignition. The 9lb hammer would not reliably ignite factory ammo but worked perfectly with the reloads we shot (.38 special cases, 148gr HBWC, 2.5grs Red Dot, Federal #100 primers (the softest primer cup primers). Polished the internals like you said you did as well as the sear, hammer notch, sides of the hammer and the insides of the frame where the hammer goes to remove any/all burrs and to polish it. Finished with a Hogue finger groove Monogrip. You wouldn't know it was a Ruger unless you looked at it up close :grin: That gun would hold it's own with any PPC gun on the line. Never used shims (didn't hear about them back then) but probably wouldn't have used them anyway as good as my revolver shot.

I wish I still had that gun. But I was in the USAF at the time and was selected to join a special maintenance team to go to Egypt to help the EAF open a new F-16 base. Sold it to a good friend and PPC shooter and lost track of it over time.

I now have a pretty fair collection of the Six series Rugers (Security, Police Service and Speed) and GP100's. I'm kind of endeared by the Ruger double action revolvers (all of them to include the SP101's and LCR's) and get ribbed by the Ruger SA collectors (all in fun). I do specialize in the repair and refurbishment of Six series and the GP100's in my small (me) gunsmithing/Cerakote business.

Bazoo, in my estimation, you will never be disappointed in purchasing Ruger double action revolvers, old or new.

[onelight]

Thanks all. I have already made both specials and magnums to test. So far I'm getting 2.5"-3" groups rested at 25 yards, but I'm working on cutting that in half. Not sure if it's me just needing to familiarize myself more with the gun or something with my loads.

There are guys here that can shoot better , but for me 21/2 to 3" at 25 yards with an iron sighted revolver is a good day.:D

[Bazoo]

Thanks xring for your post. I did some other polishing also, but in stages. The trigger opening, the sides of the hand, the hammer and trigger area for the double action pull and for cocking the single action. I can't think of what that's called right now. I didn't get wild on it, and I didn't smooth all the machine marks off. I used 600 grit sticky back paper adhered to a steel ruler and then some green polishing compound on a backer. I studied it well to make sure I understood how it worked before starting.

I removed some sharp edges and smoothed some where the trigger guard latch rubs. That made disassembly much easier.

[Shawlerbrook]

I have a used GP100 in 357 I bought in 1992. Accurate and like said above, STRONG !

[Xringshooter]

Where the trigger guard latch goes into the frame is a much missed area when people are "cleaning up" the GP100 as well as the hole that the latch and trigger return spring go into. Many don't think about those areas but it can help in the smooth functioning of the gun overall. The biggest thing when polishing around the sear and the notch on the hammer is to keep the angles the same and just polish the surfaces. You don't want to change any angles, that can lead to bad things happening, but I think you already know that.

The part on the trigger just below the SA sear is called the secondary DA pickup and on the hammer the part above the SA notch doesn't really have a name. Also, smoothing up the part above the sear (called the primary DA pickup surface) will help make the trigger pull feel smoother as that part is what first contacts the hammer dog when shooting in the DA mode.

[DougGuy]

You can ream the throats yourself, the expense comes in the piloted reamer vs. the solid nose reamer. The solid nose diameter is so much smaller than the throats, it might as well not even have a nose on it, you are pretty much going in blind without anything to keep the flutes centered.

The next thing is cleaning up the tool marks left by the reamer which will be considerable. If you are targeting .3585" which is the most requested size and which is correct for .358" boolits, you have to hope the reamer cuts small enough to leave you enough meat to finish at .3585" without leaving so much that it becomes a secondary chore to take throats out where a .358" boolit slides through with finger pressure, and then you have to be really diligent in keeping throat diameters consistent enough that it minimizes any pressure variations which will open groups measurably.

Two cylinders honed on precision equipment to a factory like 800 grit finish are considerably less than the cost of the piloted reamer, two cylinders honed and chamfered are only a tad bit more than the piloted reamer, and you still have all the cleanup to do after reaming.

I started years ago with reamers and a split aluminum rod then moved fairly quickly to the ACME laps and valve grinding compound to clean up after reaming, none of the equipment I started with or the techniques and materials I used even came close to the results and the accuracy of the Sunnen hone..

[megasupermagnum]

Where the trigger guard latch goes into the frame is a much missed area when people are "cleaning up" the GP100 as well as the hole that the latch and trigger return spring go into. Many don't think about those areas but it can help in the smooth functioning of the gun overall. The biggest thing when polishing around the sear and the notch on the hammer is to keep the angles the same and just polish the surfaces. You don't want to change any angles, that can lead to bad things happening, but I think you already know that.

The part on the trigger just below the SA sear is called the secondary DA pickup and on the hammer the part above the SA notch doesn't really have a name. Also, smoothing up the part above the sear (called the primary DA pickup surface) will help make the trigger pull feel smoother as that part is what first contacts the hammer dog when shooting in the DA mode.

You are talking about the hole in the frame/grip stud that the plunger locks into to hold the trigger guard in place? It does not move, how could this possibly effect anything? I do agree on the inside of the housing for the trigger return. Sometimes there is a huge burr in there. All I do is use the correct size drill bit, turned by my bare hand, then a good cleaning with a bore brush. I've never had my trigger stick.

[Bazoo]

Xring, yep. Thanks. I smoothed those and polished and it made a world of difference. I might shim the dog at some point because it has lots of play, but really I'm satisfied.

Doug, thanks for your explination. You're talking cylinder throats, which I haven't measured yet. I'm talking having the chamber mouths chamfered for ease of loading. I most likely will have you hone my throats if I determine it needs it.

[Bazoo]

You are talking about the hole in the frame/grip stud that the plunger locks into to hold the trigger guard in place? It does not move, how could this possibly effect anything? I do agree on the inside of the housing for the trigger return. Sometimes there is a huge burr in there. All I do is use the correct size drill bit, turned by my bare hand, then a good cleaning with a bore brush. I've never had my trigger stick.

Mine had a razors edge on the trigger guards rear tang where it locks into the frame as well as the edges of the recess it locks into.

On the spring channel, I wrapped some sticky back 600 grit on a drill bit shank followed by green polishing compound on a 22 bore mop, both spun in a drill. I also polished both cups and the end of the trigger strut.

[Xringshooter]

You are talking about the hole in the frame/grip stud that the plunger locks into to hold the trigger guard in place? It does not move, how could this possibly effect anything? I do agree on the inside of the housing for the trigger return. Sometimes there is a huge burr in there. All I do is use the correct size drill bit, turned by my bare hand, then a good cleaning with a bore brush. I've never had my trigger stick.

Yes, the hole in the frame where the trigger guard latch pin goes in. Yes, it doesn't have anything to do with the functioning of the trigger. BUT, if that hole has rough edges, or wasn't drilled properly (and it does happen) then it can make it very difficult to take the trigger guard assembly off or very hard to have the assembly seat fully (so you don't see a gap between the trigger guard and the frame) when you put it back together. I have seen this to be the cause when customers bought me their GP's because it was so hard to field strip and put back together.

[Bazoo]

It made a world of difference for me in being able to reassemble the gun.

[onelight]

It made a world of difference for me in being able to reassemble the gun.

It was an improvement on mine also. It doesn't make it shoot better but it is easier to live with.:-)

[Bazoo]

There was mention made of the GP being strong, ya don't say? How do they hold up to the old heavy loads? When I had a blackhawk in 357 I shot quite a few 358156 over 15 grains 2400. That load is much too strong for a K frame and questionable in an L frame. I've done some research and what I find is somewhat mixed. Is the strength comparable to a model 27?

In comparison to the wife's 686, there is much more frame below the barrel, and on the top strap.

[Petrol & Powder]

Strength is a little difficult to define because we're talking about a system. There are many factors involved. The strength of the cylinder, the strength of frame around the barrel shank, the strength of the top strap, the strength of the action, etc.
The GP-100 excels in many areas. The lack of a side plate helps to increase the strength of the frame. There is a lot of steel around the barrel shank. The top strap is fairly thick. The cylinder locks up to the frame in the rear like most revolvers but the second lock on the crane is particularly effective. The parts in the action are rather large and the steel used seems to be very tough.
The overall strength of a GP-100 is the sum of all of these traits. It can handle the pressures likely to be encountered and they have proven to be able to handle those pressures for many years. The action of a GP rarely breaks, in fact, they don't even seem to wear much under heavy use.

[Bazoo]

I did some testing earlier and found a load that the gun likes. Rested at 25 yards I got a 1 5/8" 6 shot group. So to make sure it wasn't a fluke I promptly repeated it.

38 special, Winchester cases, Lee 358-140-SWC sized .358, 5.0 Unique,CCI 500, BAC lube. Ill see about tightening it up more but I'm happy with my initial results. I did get a picture that I'll post next time I get to my friends house to use the internet.

[megasupermagnum]

There are two versions of strong. There is the outright strength, and then there is durability. All I will say about the former is that the GP100 came out in 1985, when the SAMMI max average pressure specification was 45,000 CUP. Many of those old loads were found to be over 40,000 PSI with the new system, but the GP100 was built to handle that level. Also, the european CIP standard is still 43,500 PSI today.

Then the durability. The GP100 came out to compete with the L frame, and from what I have seen, the GP100 is more durable. I have no idea about the N frame. I would think either one is perfectly suited for a lifetime of shooting.

[Bazoo]

I appreciate all the discussion thus far.

I am getting a bit of leading with the gun. It starts in the forcing cone and seems to build if I fire a couple boxes. But it also has a trace of lead in the rifling down the bore.

Both of my loads I've tried are 5 grains unique and either the RCBS 38-150-SWC or the Lee358-140-SWC. Both in special brass and with BAC lube. I've tried both ww alloy and a softer alloy, 50/50 ww/Pb I'd guess. Sizing them .358

I slugged the bore which is 5 grooves. Using a soda can shim the best I can figure it's .354. I've re-measured it and really tried to get a good feel and a light measurement. I can feel some change in the resistance when going through the area of the barrel where it threads into the frame. It's not a huge change though.

So I run as tight a fitted patch on a brass jag(didn't have a plastic one) as I could get started down the bore and it didn't get tighter at the threads. Now if I'm not mistaken Doug was suggesting this method with a plastic jag to feel for tightness. Will it not work with a brass jag or is the danger just getting the jag stuck?

I slugged just the muzzle by inserting a brass rod in the bore to tap the slug back out and it was .354 too. Seems small for a 357 bore, don't ya think? Is this common for Rugers? Looking back, I'm going to remeasure this.

I slugged the cylinders they all measure .3575. Yes all this with calipers as I don't have a micrometer.

So my query, Will sizing the bullets over throat diameter cause leading in of itself? Where should I go from here? Straight to having the throats opened up?

Should I buy a selection of pin gages? And if so, which sizes. Minus Z gages right?

[megasupermagnum]

The GP100 I bought a month and a half ago has a groove diameter that is right at .3570" as best I can measure. If you had a notable constriction, you would feel it with the patch. I had a S&W with a .002" constriction as determined by pin gauges, and a tight patch was very tough to get through, as in had to hit the rod with my palm. If you pushed a slug all the way through, and then did one only at the muzzle, and both measured the same, I wouldn't worry about it. I don't like the soda can wrap for measuring 5 groove. It always seems to read around .001" small for me. If I conpare the same slug from my model 57, measured with soda can is around .407", with a vee block, reads .4082". Maybe Ruger used to use 9mm barrels?

The very first place I now look for problems, after checking the gun as you have, is to check the brass. Pull a bullet, and make sure it is still .358"

[Bazoo]

Will do MSM, thanks. I had forgotten about that.

[Bazoo]

I have fire lapped the gun, http://castboolits.gunloads.com/showthread.php?403384-Leading-in-my-GP100

Yesterday I fired a box of test cartridges made with 16-17 grains 296 powder, CCI 550, and RCBS 38-150-SWC bullets sized .357 and lubed with 50/50. I got several 1.5" groups and settled on 16.8 grains for a box to test farther. None showed pressure signs, but 17 grains seemed to start opening groups back up. I was able to hit my 6" plate at 100 yards though.

I wasn't having the best day for my eyes and hands, so testing wasn't perfect, but satisfactory for now.

[derek45]

https://youtu.be/Umk68uyVxtA

Love mine