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GP100 action binding


Fishbreath
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Lots of topics being thrown around here, but if you've determined that you have insufficient clearance between barrel and cylinder, then you need to fix that problem.  Get rid of the excessive endshake first, then if the gap is still too small, hit the back of the barrel with a big flat file that has a safe edge.  Keep it perpendicular and watch to make sure it's taking off metal evenly.  A few good strokes should do the trick.  Sounds a little caveman, but it absolutely works.  

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On 4/16/2021 at 9:50 PM, Carmoney said:

Lots of topics being thrown around here, but if you've determined that you have insufficient clearance between barrel and cylinder, then you need to fix that problem.  Get rid of the excessive endshake first, then if the gap is still too small, hit the back of the barrel with a big flat file that has a safe edge.  Keep it perpendicular and watch to make sure it's taking off metal evenly.  A few good strokes should do the trick.  Sounds a little caveman, but it absolutely works.  

 

 

and here I am pretending that i've never taken a file to my forcing cone during a match 

 

🤣

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A successful range trip in the books!

 

Before the trip, holding up the gun to a light, I noticed that the forcing cone wasn't quite square—closer to the cylinder face on the top than the bottom. A few passes with a file flattened it out.

 

I got through 180 rounds with only one trigger hitch, although granted I scrubbed the cylinder face and forcing cone with a brass brush 2-3 times through that stretch.

 

2.8gr of Clay Dot seems like it'll be the ticket. 2.7gr gives me 127PF over 10 rounds, which is a bit cozy for my comfort. I think I might have accidentally loaded my 2.8gr testers with 2.9gr, since they were nearly identical to my 2.9gr testers (864.2, stddev 14.6; 865, stddev 18.6). Those 60 rounds left a whitish residue on the cylinder, and toward the end, I started having some hitching in the trigger. Forcing cone/cylinder face cleaning did the trick, and so also after the second occurrence, midway through my practice ammo for the day (loaded with Bullseye). Maybe I'll try an endshake shim again, now that the forcing cone is cleaned up.

 

The other minor frustration is continued trouble with light strikes, somehow— even running a 10lb hammer spring on Federal primers (although magnum, instead of regular, because it's all I was able to find), and making sure the primers are all seated as deep as I'm reasonably able to do on my Lee turret press, I'm having issues. I guess maybe I'll order an 11lb hammer spring for now, and see if I can find a good source on what additional things there are to slick up.

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Posted (edited)

I had zero light strikes at today's match, and one getting in a bit of practice after the match had ended: I filed the hammer stop down a little more. I think I might even go a little further—people on Ruger forums talk about taking it down until the hammer step is only 0.005"-0.006" taller than the transfer bar, and I think I have a little further to go yet. The easier measurement to take is firing pin clearance to the back of the cylinder—I'm at 0.015" right now. If I can get through, say, 500 rounds with no light strike trouble, I might countenance trying the 9lb spring again.

 

I did, however, have trouble with the cylinder binding again. I'm thinking it might be heat-related—it happens a little ways into a stage—but it didn't happen when I dumped the 40 rounds left on my belt after the last stage as quick as I could after the match. The pictures below are how the cylinder and forcing cone looked after those 40 rounds, plus a few more slow fire. Is that an ordinary amount of debris/fouling to be seeing? Is the whitish residue powder or lead? (I haven't cleaned yet, so I can still do any tests to suss out which it is.)

 

I did notice once or twice that when I had binding problems, the daylight visible in the barrel/cylinder gap looked thinner than it looked after a good scrubbing with the brass brush, so it may be that the gap is a bit too tight, and a few passes on the forcing cone with a file are called for. (I think I'll have to go get a wider file tomorrow if so—all of mine are the wee skinny kind.)

 

Anyway, gun problems aside, I had a pretty solid day, at least. Movement and reloads are feeling good, and I shot an 86% run on CM 18-04 today. (If I'd hit one more A, it could have been a GM run!)

 

e: I found this thread at The High Road, which speaks to a similar problem. Unfortunately, it doesn't speak to a solution beyond 'find the right load'.

 

8IzVBnrlRX6RGiBttXQjQQ.jpeg

Ty_mjSLhQT-l2xBsU51cmQ.jpeg

EcuFdqgjRaKKfA29s6DQpQ.jpeg

Edited by Fishbreath
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The white is major lead splatter. Either the lead is too soft or not a good lube or the forcing cone is too small. I would recut the forcing cone with an 18 degree cutter and see if that doesn't clear things up. The fact that it's fairly even all the way around points to too small an entry way as opposed to the cylinder being out of time and off to one side. That is a heavy amount of leading that would definitely bind things up.

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Posted (edited)

Thanks so much for sharing your expertise, guys—seeing a light at the end of this particular tunnel is a tremendous relief, and I wouldn't be nearly as close if not for this forum and the knowledge so readily spread.

 

These are coated bullets (Ibejiheads), and I think I've seen similar symptoms with plated bullets (Xtreme), but I suppose that probably doesn't make much of a difference, with how thin the plating/coating usually is? As further confirmation, when I was shooting factory .38 Special FMJ, I had no problems at all, and don't think I had very much trouble with the first kind of coated bullets I used (SNS 158gr, I think?).

 

I tried dropping one into the forcing cone. I'm not sure how it's supposed to look, but it seemed to go a pretty good way in, with decent clearance all around:

 

i5qkuQETQfONQ_kHmNV9TA.thumb.jpeg.97df451f84c8669f75cdc548b07488ce.jpeg

 

I wasn't able to push one through a chamber throat without tapping it with a brass punch and hammer, and when it came out the far side, it had scratches on it that went deep into the coating, or through it in some places.

 

OWYDOfpARGGfR6FznqNRVA.thumb.jpeg.45a7b3c5c2b7c90335a492e05941162e.jpeg

 

Could it be too fat a bullet for the chambers, rather than a forcing cone problem, or is a too-tight forcing cone still the most likely culprit?

 

edit: these are .357" bullets, and calipers say they're very slightly oversize on average—.3575", say. The one I pushed through the throat measures about .357" on the dot.

Edited by Fishbreath
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14 hours ago, Fishbreath said:

Thanks so much for sharing your expertise, guys—seeing a light at the end of this particular tunnel is a tremendous relief, and I wouldn't be nearly as close if not for this forum and the knowledge so readily spread.

 

These are coated bullets (Ibejiheads), and I think I've seen similar symptoms with plated bullets (Xtreme), but I suppose that probably doesn't make much of a difference, with how thin the plating/coating usually is? As further confirmation, when I was shooting factory .38 Special FMJ, I had no problems at all, and don't think I had very much trouble with the first kind of coated bullets I used (SNS 158gr, I think?).

 

I tried dropping one into the forcing cone. I'm not sure how it's supposed to look, but it seemed to go a pretty good way in, with decent clearance all around:

 

i5qkuQETQfONQ_kHmNV9TA.thumb.jpeg.97df451f84c8669f75cdc548b07488ce.jpeg

 

I wasn't able to push one through a chamber throat without tapping it with a brass punch and hammer, and when it came out the far side, it had scratches on it that went deep into the coating, or through it in some places.

 

OWYDOfpARGGfR6FznqNRVA.thumb.jpeg.45a7b3c5c2b7c90335a492e05941162e.jpeg

 

Could it be too fat a bullet for the chambers, rather than a forcing cone problem, or is a too-tight forcing cone still the most likely culprit?

 

edit: these are .357" bullets, and calipers say they're very slightly oversize on average—.3575", say. The one I pushed through the throat measures about .357" on the dot.

You can get a reamer from Brownells, don't cost much, to cut the forcing cone.  Clymer makes one that's an 11 degree I used on my 44 and 45 revolvers.  ?Supposed to be more accurate? Not sure about that, but cleaning up and smoothing out is always good.

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Just now, pskys2 said:

You can get a reamer from Brownells, don't cost much, to cut the forcing cone.  Clymer makes one that's an 11 degree I used on my 44 and 45 revolvers.  ?Supposed to be more accurate? Not sure about that, but cleaning up and smoothing out is always good.

 

I came across 4D Rentals, which rents both chamber throat reamers and forcing cone reamers with the whole kit and caboodle.

 

Rugers come from the factory with a 5-degree forcing cone, I'm told. What are the implications of cutting a sharper angle in?

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3 hours ago, Toolguy said:

Forcing cone looks big enough with a bullet in it. I would ream the cylinder throats to.358.

Or try .356" bullets first.

 

Edited by pskys2
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3 hours ago, Fishbreath said:

 

I came across 4D Rentals, which rents both chamber throat reamers and forcing cone reamers with the whole kit and caboodle.

 

Rugers come from the factory with a 5-degree forcing cone, I'm told. What are the implications of cutting a sharper angle in?

The theory is a more gradual forcing cone allows the bullet to center without so much disruption, like banging or skidding into the side of the forcing cone.  Thereby the bullet will spin more true.

For a Revolver, I'm not sold but when I planned on doing it I decided to try it.

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15 hours ago, Fishbreath said:

 

Unfortunately, I have another 2400 or so .357" bullets, so reaming to .358" seems like the more expedient course. >.>

Not really can't put metal back.

It's a .38 right?  And you're using .357 coated?  Undersized bullets and dirty powder can cause issues.

Being as 38 special fmj's didn't cause any issues, I'd focus on the powder first.

Have you measured the actual bullet diameter, not what they say it is?

As much as I hate to say this but if it doesn't get better it may need a trip to TK or Olhasso for finessing.

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2 hours ago, pskys2 said:

It's a .38 right?  And you're using .357 coated?  Undersized bullets and dirty powder can cause issues.

 

Yes and yes. I'm on to Clay Dot shortly, which will hopefully solve any dirty-powder issues from Bullseye.

 

2 hours ago, pskys2 said:

Being as 38 special fmj's didn't cause any issues, I'd focus on the powder first.

Have you measured the actual bullet diameter, not what they say it is?

 

.38 Special FMJ worked for 700 rounds with no trouble. The bullets measure slightly more than .357" on my dial calipers, but probably less than .3575". The chambers all read .356" to .357" on the dial calipers, except for one at a hair under .356". I've found a number of Ruger people noting that Rugers frequently have tight chambers, and that FMJ will mask problems with slightly-undersize chambers that coated or plain lead won't.

 

Over the past year, I've had the following results with the following bullets:

  • Factory .38 Special FMJ (Prvi Partizan, .3555"): no problems at all.
  • Xtreme 158gr RNFP (.357") in .38 Special handloads: no problems.
  • SNS 158gr RN (.358") in .38 Special handloads: minor problems—I don't recall serious cylinder binding, but going back over my video from the match where I used most of them, I do see some buildup/splash on and around the forcing cone toward the end of the day.
  • Berry's 158gr RN (.357") in .38 Special and .38 Short Colt: minor problems at first, serious problems lately.
  • Ibejiheads 158gr RN (.357", measured at up to .3575") in .38 Short Colt: gives up after 20 rounds tops, at least in matches. (Lasted 40 or 50 between cleanings in practice, though.)

The serious problems have so far all happened after switching to .38 Short Colt—could moving to the shorter case in combination with narrow throats exacerbate things?

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Gage pins are the best cheap way to measure hole sizes. Good investment. They are easy to use and give accurate readings with minimal training and experience. Other methods require you to develop a "feel" for the measuring device.

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I ended up getting a DIY .38 throat set on Amazon—a la carte spares, from .354 to .358 in .001 intervals. Maybe someday I'll spring for a whole set.

 

Iowegan, from rugerforum.net, has a guide to GP100s, which looks like an excellent piece of reference for we few Ruger shooters.

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Pin gauges came yesterday, and all of my chamber throats passed a .357 gauge but not a .358. The throat reamer from 4D Rentals came today, so I did that job. The chambers now let a bullet through with light to moderate finger pressure, and the .358 gauge fits like a glove.

 

Range trip tomorrow to verify that it's improved things.

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Alas, still fairly serious leading issues. I'm inclined to think the bullets, at this point, but as I said, I also had some trouble with Berry's pre-ream, which I'd expect to be a little more resilient to leading issues than coated.

 

2124434912_PXL_20210502_1804028352.thumb.jpg.ab57170e6ac6eac1c0a6311a731cfd06.jpg

 

Not quite sure where to go from here. Any ideas, beyond trying some other bullet sizes/brands?

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29 minutes ago, Fishbreath said:

Alas, still fairly serious leading issues. I'm inclined to think the bullets, at this point, but as I said, I also had some trouble with Berry's pre-ream, which I'd expect to be a little more resilient to leading issues than coated.

 

2124434912_PXL_20210502_1804028352.thumb.jpg.ab57170e6ac6eac1c0a6311a731cfd06.jpg

 

Not quite sure where to go from here. Any ideas, beyond trying some other bullet sizes/brands?

 

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Posted (edited)

I have not had the leading issues with Ibejiheads like you’ve had. Alec has shot more of them than me so he might have better insight.

 

Can you run those Ibejiheads in a 38 special load for a bit to see if you get the same issue?

Edited by RangerMcFadden
Wasn’t clear saying “38”
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27 minutes ago, RangerMcFadden said:

Can you run those Ibejiheads in a 38 special load for a bit to see if you get the same issue?

 

I'll make some up for testing this week.

 

Are you crimping at all? If so, how much? I had a fairly aggressive taper crimp (with a 9mm die) set up from when I was running plated, which seemed to want it. Maybe the Ibejiheads aren't liking it?

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