GP100 DIY trigger job

I have a SS 4.2” GP100 that I bought new about 5 years ago.

One of the first things I did after bringing it home was install Williams Fire Sights fiber optic sights front and rear. In single action it is one of my favorite handguns to shoot. The sight picture in adequate light is precise. The heaviness makes .38 special tame and full-house .357 manageable.

The single action trigger has always seemed adequate.The double action trigger pull on the other hand, was almost unusable, even after the thousands of rounds I’ve put through it and dry firing I’ve done.

I happened to pick up a Match Champion, a Smith, and a new Colt King Cobra last week and it made me realize how awful the trigger was on mine. So, i reached out to a local gunsmith about doing a trigger job. He was backlogged as is everyone at this time. So I decided to tackle the job myself.

I ordered a set of springs from Wilson Combat and started reading and watching everything I could about the subject while I waited for them to arrive. I found a pdf called Lowegan’s book of knowledge that thoroughly detailed the inner workings of my gun and gave general advice about improving the action.

The day before the springs arrived, I almost completely disassembled my revolver (for the first time ever) and cleaned everything thoroughly. I then took a Dremmel tool with a felt polishing tip and polished all the recommended touch points with Flitz paste to smooth out the action. I was careful to avoid taking any metal from the hammer and sear. It was easy to see where the trigger parts had been touching so I polished those really well. I also smoothed out the trigger return housing by hand-turning a 13/64 drill bit inside the cavity.

I then put it back together dry and clean to see what effect the polishing had. There was a noticeable difference. The DA pull was still heavy but it was much smoother. The SA break was crisper as well.

The next day the springs arrived. I installed a 10# hammer spring and an 8# trigger spring, lubed everything with oil, and went to test reliability. 4 out of 100 rounds loaded with CCI 550 small pistol magnum primers failed to fire in double action. So, when I got home I removed the 10# hammer spring and installed the 12#.

Here are the before/after lbs.of pull at each stage with a subjective feel description:

Stock (14# hammer spring,12# trigger return spring, no internal polishing, 5 years of use)
• DA - 12 + with a long, 3 stage, heavy pull
• SA - 6 with a fairly okay break

After polishing internals:
• DA - 11.5 with a smoother 2-stage pull
• SA - 5.6 with a crisper, cleaner break

With 10#/8# spring combo
• DA - 8.3 with a less pronounced stack at the end
• SA - 3.8 crisp and clean

With 12#/8# spring combo
• DA - 9.5 with the same slight stack as 10# spring, a little disappointingly heavy compared to 10# spring but WAY better than with stock spring
• SA - 4.3 with same crisp and clean break

I could probably do way better with some shims where appropriate. Stoning internal touch points would be more effective also but fear of taking off too much metal makes me nervous. Still, I achieved a DA trigger I can actually use and a much improved SA trigger pull. I would compare my results with the 10# hammer spring installed with the Smith’s trigger I tried. I suppose I could reinstall it and use softer Federal primers exclusively. Maybe soon I’ll get into it again and try to make the 10# spring reliable with all primers. For now though, I’m happy with the improvement I made.

Cost:
Springs - $9.99 + $9.99 shipping
Dremmel tool and attachment - $54
Flitz - $9
Total - $83

Update: I found a feeler gauge in my tool box. Just for giggles I used it and found there is .011 of play in the hammer. I ordered some hammer shims and hope they will smooth it out enough to use the 10# spring with 100% reliability.

I don’t own a trigger scale either. I do have a precise 30 kilogram scale though. I fed kite string through the trigger guard, cut about an 18” length and tied an end to each side of the handle of a 5 gallon bucket. I then placed the kite string on the bottom part of the trigger and let the bucket hang free while holding the revolver up. I filled the bucket with water until the trigger broke and weighed the bucket and water to get the lb. of break.

I plan on dabbing some Hoppe’s gun grease on the shims to “glue” them in place for installation.

UncleEd said:

No, you did not get lucky.

Bashing Ruger triggers has always been very
fashionable when reporting on them vs. the
usual triggers found on a S&W.

Neither company puts out very bad trigger
pulls although often heavier than a lot of
users wish.

A point or two in Ruger's favor is that the
company puts out videos on breaking down
their handguns and doesn't seem to mind
people believing they are all instant
gunsmiths.

As a result, the world--or rather the internet
and gun forums---is full of gunsmithing
commentary, often of the negative sort.

Oh, just to set the record straight, I am a
fanboy of S&W revolvers but I do like Rugers
too. And the Smith Model 15 is my all-time
like model.

Click to expand...

I have read stories multiple times of folks getting a subjectively great trigger on a Ruger out the box. When I bought my GP100, I had no point of reference for trigger quality like many of you. I just knew that my single action was fine and the double- action was almost unusable. I thought it was a safety feature. It wasn’t until years later that I realized there were better triggers available. By that time, I was so accustomed to SA only that it didn’t matter much. Honestly, the whole experience has been positive for me. I got to see how my revolver works and what affects the subjective feel and measurable pull weight of a trigger. I am coming to realize that smooth but a little heavy can be subjectively “better” than gritty and a little lighter.

JohnKSa said:

I don't change springs in my Ruger revolvers, so take that as the context for my comment below:

Click to expand...

I did that by hand turning a drill bit in there. I’m sure it helped.

Update: I ended up shimming my hammer. It had .011 play and rub marks. I ordered two .004 shims from Triggershims.com for $6.

I need to brag on them a bit. In these slow mail/shipping times, my shims came in quickly. I ordered them on Sunday night. They shipped Monday morning and arrived Thursday. I got a personal email from Lance the owner early on Monday morning, thanking me for my purchase. They have a great selection, how-to videos, and fast shipping. If you haven’t measured already, they have feeler gauges for sale to measure to the thousandths and shim kits to address what you find. Plus, they didn’t tack on anything for shipping and handling like many companies do, even for lightweight items. I’d buy from them again.

Anyway, I put one on either side. It made the double action pull so much smoother than it already was that I went ahead and put the 10# hammer spring back in. I’ll be testing ignition on magnum primers today. If it ends up being reliable, I’ll have a legitimately useful DA trigger on a gun that didn’t before. More than useful - it’s actually pleasant.

BTW - After having accomplished improving my GP100, I got a little cocky and took my Single Six apart to see what I could do with it. That’s a completely different animal. I also have a “Old Model” Vaquero in 45 Colt I was thinking about. After struggling a bit with the Single Six, I may just leave well enough alone. It made me realize how user-friendly the takedown is on the GP/SP type actions.

Final report: With hammer shims and 10# mainspring, WSPM and CCI 550’s ignited every time. GTG.