Adventures in the Ruger GP100

[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/show...ng-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]

Love mine