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Ruger hammer stop filing: how much is too much? (also, Super GP100 tuning log)


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I'm trying to get my Super GP100 to be a bit more tolerant of less-than-ideal primer depths and very slightly bent moon clips, without having to go back up the ladder in terms of hammer springs. One option of which I've heard is removing material from the stop at the top of the hammer, the bit which rests against the frame, so as to smack the transfer bar a little harder and push the firing pin a little further.

 

Before I got my 1/1000" calipers, I took a little material off, and the depth gauge says 0.071" from the hammer stop to the hammer face. How much further can I go? Obviously, it's a situation where taking too much off would be a giant pain and necessitate a replacement hammer.

Edited by Fishbreath
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1 hour ago, Fishbreath said:

I'm trying to get my Super GP100 to be a bit more tolerant of less-than-ideal primer depths and very slightly bent moon clips, without having to go back up the ladder in terms of hammer springs. One option of which I've heard is removing material from the stop at the top of the hammer, the bit which rests against the frame, so as to smack the transfer bar a little harder and push the firing pin a little further.

 

Before I got my 1/1000" calipers, I took a little material off, and the depth gauge says 0.071" from the hammer stop to the hammer face. How much further can I go? Obviously, it's a situation where taking too much off would be a giant pain and necessitate a replacement hammer.

I remember seeing a thread about doing this to a GP100 22 on the Ruger Forum. It includes pictures on how to make a jig to hold the hammer.

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This looks like the one. (edit: no instructions for hammer jig, but some good tips anyway.)

To reproduce some of the information here:

  • The original poster in that thread took 0.006" off of the hammer stop; more caused reset issues because of transfer bar pinching. (If I run into that, I've gone too far, but it seems like the kind of thing that could be salvaged by transfer bar/hammer face polishing.
  • I probably need to shim the cylinder for endshake reasons, although I won't know that for sure until my feeler gauges get here on Monday.
  • Bowen makes an extended firing pin I can try, which uses (or can use) shims to set protrusion.

Thanks for the pointer!

Edited by Fishbreath
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20 minutes ago, Fishbreath said:

This looks like the one. (edit: no instructions for hammer jig, but some good tips anyway.)

To reproduce some of the information here:

  • The original poster in that thread took 0.006" off of the hammer stop; more caused reset issues because of transfer bar pinching. (If I run into that, I've gone too far, but it seems like the kind of thing that could be salvaged by transfer bar/hammer face polishing.
  • I probably need to shim the cylinder for endshake reasons, although I won't know that for sure until my feeler gauges get here on Monday.
  • Bowen makes an extended firing pin I can try, which uses (or can use) shims to set protrusion.

Thanks for the pointer!

Check your messages.

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  • Fishbreath changed the title to Ruger hammer stop filing: how much is too much? (also, Super GP100 tuning log)

I decided not to build the jig and take a little more off by hand. Measuring between the two points in the picture (ignore the frame marks on the hammer, they're from a day when I didn't realize I'd missed a shim when putting the hammer back in), I went from 0.072" (my first measurement, after a bit of halfhearted filing prior to having a tool that could reliably measure 0.001") to 0.065". At 0.065", I can just start to feel the transfer bar binding at the start of the trigger reset, so I'm going to leave it at that.

 

Next thing on my list are more shims—I have a few coming from TriggerShims.com for the cylinder, the hammer dog, and the hammer (I know it's not touching the frame much, but I'd like to be sure it's not touching the frame at all).

PXL_20201018_163909969.jpg

Edited by Fishbreath
Fix hundredths->thousandths error
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