Trigger pull weight - slide on (4.75lbs) vs slide off (2.9lbs) - RimfireCentral.com Forums

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  #1  
Old 11-05-2018, 04:07 PM
rdas
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Trigger pull weight - slide on (4.75lbs) vs slide off (2.9lbs)



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Why would having the slide installed significantly increase the trigger pull weight?

My 1992 Gold Target has a fairly gritty, relatively heavy trigger pull of 4.75lbs with too much weighted pre-travel (creep), compared to my 1990 Target (about 2.75lbs with almost no creep) or my 2016 Hunter that has a Silhouette sear spring in it (2 lbs with only a little creep). The purpose of the Gold Target is for use as a CMP 22 EIC pistol, so my goal is for it to have a nice, smooth, crisp 2lbs trigger with very little weighted pre-travel/creep or over-travel. It has the trigger stop screw, so I've dialed out most of the over-travel. It has the sear spring adjusting screw, but I wanted to get close to 2lbs first, and then use that for fine final adjustments.

I started working on it yesterday, and noticed that the pull weight seemed much less after I removed the slide (using my thumb as a hammer-arrestor). My trigger pull gauge confirmed it... about 2.9lbs with the slide removed. Put the slide back on just to confirm it... 4.75lbs again. Took the slide off... still 2.9lbs. I noticed that, based on the marks on the inside of the slide, the right end of the sear arm appeared to be rubbing the inside of the slide. That would do it. I also noticed that the left side of the sear appeared to be rubbing against the inside of the frame (near the top of the sear), which could also be caused by the slide contacting the right end of the sear and pushing it to the left.

So I did the obvious, and stoned the right end of the sear arm down a bit. (I also straightened the edges of the hammer and sear, to clean up the trigger let-off.) Put the slide back on... still 4.75lbs (but the let-off is noticeably better).

So, now I'm a little stumped. I did not see any obvious marks indicating that the disconnector is rubbing against the slide, but will do more investigation into that. What else could cause the slide being installed to add nearly 2lbs to the trigger pull weight?

A little background... I bought the gun in well-used condition, so I cannot confirm or deny which parts are original. It has a new mainspring, and a de-mushroomed firing pin, because when I got it, it was having light-strike issues. It also has a new hammer link, because the old one was very worn. I had to grind down the end of the new link to make it function, but it's still longer than the previous link was. I also had to replace the tombstone-shaped recoil guide (was broken), and buffer (was missing). Otherwise it's running the parts that came in it. I've fired several hundred rounds through the gun since all that work was done, and it works as expected (feeds, fires, cycles, ejects, etc. with no issues).

Dave
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  #2  
Old 11-05-2018, 08:15 PM
Nolan

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Quote:
Originally Posted by rdas View Post

A little background... I bought the gun in well-used condition, so I cannot confirm or deny which parts are original. It has a new mainspring, and a de-mushroomed firing pin, because when I got it, it was having light-strike issues. It also has a new hammer link, because the old one was very worn. I had to grind down the end of the new link to make it function, but it's still longer than the previous link was. I also had to replace the tombstone-shaped recoil guide (was broken), and buffer (was missing). Otherwise it's running the parts that came in it. I've fired several hundred rounds through the gun since all that work was done, and it works as expected (feeds, fires, cycles, ejects, etc. with no issues).

Dave

I'm away from home so I can't go take one of mine apart to look, but the only thing I can think of would be the new longer hammer link puts a little more pressure on the hammer/sear because the hammer is being held slightly further down by the slide than when the slide is removed?

On second thought, I would think that would actually relieve pressure on the hammer/sear? Is the wear on the hammer where the slide against it even and square? If the slide was putting more pressure on one side of the hammer?

Nolan
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  #3  
Old 11-06-2018, 02:24 AM
Nolan

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Now that I've had a minute or 200 to think about it, the slide isn't or at least shouldn't be touching the hammer when it's in battery so that's probably not causing the heavier trigger pull.

What things COULD be different with the slide on and in battery? Could the disconnector/trigger bar be too tall and is being held slightly out of position even when it's in the disconnector notch? With your third hand, try holding the disconnector down just slightly, use another thumb as a hammer stop and pull the trigger with your other hand and see if that changes the trigger pull? Have you tried backing off the over travel screw? Could the slide be pushing/moving the Safety or the Click Plate? Is there any difference in trigger movement with the hammer down (uncocked) with the slide on versus slide off?

Nolan
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Old 11-06-2018, 12:09 PM
rdas
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Quote:
Originally Posted by Nolan View Post
Now that I've had a minute or 200 to think about it, the slide isn't or at least shouldn't be touching the hammer when it's in battery so that's probably not causing the heavier trigger pull.

What things COULD be different with the slide on and in battery? Could the disconnector/trigger bar be too tall and is being held slightly out of position even when it's in the disconnector notch? With your third hand, try holding the disconnector down just slightly, use another thumb as a hammer stop and pull the trigger with your other hand and see if that changes the trigger pull? Have you tried backing off the over travel screw? Could the slide be pushing/moving the Safety or the Click Plate? Is there any difference in trigger movement with the hammer down (uncocked) with the slide on versus slide off?

Nolan
The slide should not be touching the hammer when it is in battery, so I also couldn't think of how/why the slightly longer hammer link would affect the trigger pull weight with the slide installed versus not installed.

I haven't tried playing with the trigger stop (over-travel) screw, but I can't see how that would affect the trigger pull weight differently based on the slide being installed or not.

The only things I can think of that would have this effect are:
1) The disconnector is dragging against the slide. This seems like the most likely cause, but there weren't obvious wear marks on the disconnector. I don't have it in front of me right now, but I recall that the top of the disconnector hump is noticeably worn. Maybe it's also mushroomed a bit there, and that's dragging on the slide???

2) I didn't stone the sear arm enough, and so the sear arm is still dragging against the slide. I'm planning to test this tonight by putting some marker ink on the inside of the slide, but if this was the culprit, I would have expected at least some improvement based on the work I already did.

3) The sear is rubbing on the safety, but only when the slide is installed. I'm struggling to see how this could be slide-related (left grip, maybe, but slide?), but I suppose it's possible.

4) Somehow, when the slide is installed, and I rack the slide, the disconnector, hammer, or sear is getting knocked out of alignment, and thus rubbing or catching on something, causing the increase in pull weight. This seems least likely.

I should have time to work on it again tonight, but at the moment, I'm still stumped, and looking (hoping) for other suggestions.

Thanks,
Dave
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  #5  
Old 11-06-2018, 12:49 PM
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Have you tried putting on a different slide to see if it does the same thing? Maybe a bump or a burr somewhere on the slide.

With the slide installed, try putting the safety on and pulling the trigger. Then take the safety off and check the pull. If it drops to the same as without the slide, your sear is worn and needs replaced. I bought a used Ruger that exhibited this same strange problem until I replaced the sear.
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  #6  
Old 11-07-2018, 07:35 PM
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Quote:
Originally Posted by rdas View Post
I haven't tried playing with the trigger stop (over-travel) screw, but I can't see how that would affect the trigger pull weight differently based on the slide being installed or not.

The only things I can think of that would have this effect are:
1) The disconnector is dragging against the slide. This seems like the most likely cause, but there weren't obvious wear marks on the disconnector. I don't have it in front of me right now, but I recall that the top of the disconnector hump is noticeably worn. Maybe it's also mushroomed a bit there, and that's dragging on the slide???

Thanks,
Dave
On some slides the disconnector notch is shallower than on others, so the top of the disconnector needs to be filed down a little bit to allow the disconnector/trigger bar to rise enough to fully engage the sear arm. I'm not home so I can't look to see if a low disconnector/trigger bar moves the trigger closer to the frame bringing the overtravel screw into slight contact with the frame.

Nolan
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  #7  
Old 11-08-2018, 03:51 PM
aprilian
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Are grips on or off? Was it the same for both tests? If 2# is with grips off and higher with grips on, it sounds like the trigger pin or disconnector bar is fouling on the grips.

My next guess would be that the top of the disconnector bar is rubbing on the slide somewhere. - look for marks on both and if unsure, use Dykem to see where the trigger bar is rubbing when the slide is installed.

Another place to look is the disconnector bar notch and how it mates with the sear nub. if they align without the slide and the slide knocks them into a "binding" condition, that would change the pull.

It would be easier to find hands-on. Good luck.
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  #8  
Old 11-13-2018, 01:14 PM
rdas
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Sorry for the delay. I finally had a chance to work on it over the weekend. The short answer is... the disconnector is hitting the slide, and that's why the trigger pull is much worse when the slide is installed.

It's not what/where I expected, though. It's actually the top/front of the disconnector hump that is contacting the "ramp" on the slide (that pushes the disconnector down when the slide cycles). The contact point is show in the two photos below.

The photo below is of the inside right side of the slide, from below the slide, looking up. The photo is a little blurry, but you can see the shiny spot where the sharpie ink has been worn off. The arrow is pointing to the shiny spot.
http://guns.dsttr.com/img/HeavyTrigg...111_013517.jpg



The photo below is of the disconnector, specifically the top of the disconnector hump. Again, the shiny spot, pointed to by the arrow, is where the disconnector is contacting the slide.
http://guns.dsttr.com/img/HeavyTrigg...111_013542.jpg


Note that the contact there is only from pulling the trigger. There was no slide movement, beyond pulling it straight up off the frame to look at where the contact was (as straight up as I could manage, at least).

What's happening is that, as I'm pulling the trigger back, the disconnector is being pulled forward, and the top of the disconnector hump is hitting the ramp on the slide. As trigger movement continues, the disconnector is moving forward, but also down, scraping along that ramp machined into the slide. Ideally, the disconnector should only move forward, and your finger should only have to fight the disconnector spring, sear spring, and hammer/sear friction (yeah, there's also friction of the trigger rotating on the trigger pin, the disconnector pin against the disconnector, and the sear rotating on the sear pin, but those should be relatively small forces, if those parts are clean).

Some cautious stoning of the disconnector hump has reduced the size of the contact point, and dropped the trigger pull to around 3.25lbs with the slide installed. More work is needed so that there is no contact at all; hoping to get to it in the next couple days.

If you need to do this to your Buckmark, make sure that you do not shorten the hump or dramatically change the rounded profile. The slide needs to push the disconnector down when it cycles, and you don't want it to catch or have excessive resistance when cycling. Also note that the disconnector is probably only surface-hardened, so if you have to remove a lot of material, you will need to watch to excessive wear on the disconnector hump over time (as your count of rounds fired through the gun climbs).

Dave
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  #9  
Old 11-13-2018, 02:59 PM
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I wonder if a little dab of gun grease on the disconnector hump would help? Just a thought.
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Old 11-14-2018, 06:29 AM
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That's interesting and a good catch. I was really wondering what could have been causing the difference in pull.

It's difficult to tell from the photo, but the slide looks like it could use a little smoothing on the underside, especially to break the edge where the disconnector cutout meets the flat. One of my first Buck Marks wore the disconnector down to the point it wouldn't "disconnect" after about 12,000 rounds.
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Old 11-14-2018, 11:48 AM
rdas
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That's interesting and a good catch. I was really wondering what could have been causing the difference in pull.

It's difficult to tell from the photo, but the slide looks like it could use a little smoothing on the underside, especially to break the edge where the disconnector cutout meets the flat. One of my first Buck Marks wore the disconnector down to the point it wouldn't "disconnect" after about 12,000 rounds.
Yes, the machining on the inside of the slide is what could generously be called "rough". Where the disconnector cutout was made, they cut a little too deeply (too far to the right side of the slide), resulting in a pair of edges on the lower part of the slide. The forward-most edge (extension of the ramp) is what the sear arm was hitting as the slide was cycling. Firing the gun had already worn it down quite a bit, but I stoned the right side of sear arm to further reduce that contact, especially because that contact was forcibly pushing the sear to the left, causing it to rub against the inside of the frame on the left. I did not see evidence that the disconnector is contacting those edges.

It has definitely occurred to me that the machining on the slide is really the culprit here, rather than the disconnector or the sear, but I prefer modifying the cheaper parts first. Besides, the gun does function, I'm just trying to improve the trigger. So, I'm trying to avoid replacing the slide (which is an old-style slide, of course), which might introduce other fitment issues.

I'm contemplating trying to smooth the ramp itself, and it's lower transition edge, to reduce wear on the disconnector when the slide cycles, but that's secondary to improving the trigger.

Thanks,
Dave
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Old 11-15-2018, 03:21 PM
rdas
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Quick update... I stoned down the disconnector hump some more last night. Now it does not contact the slide at all during the trigger pull. And now the trigger pull is the same with the slide on or off. Yeah!

Side note... I tried adjusting the pull weight with the sear spring adjusting screw, but it didn't help much. I unscrewed it until it hit the stop pin (a little more than 1 full turn from where it was), and it didn't make a measurable difference. I then screwed it in 4 full turns (any more, and it might fall into the frame). Still about the same average pull weight, but it was less consistent (sometimes up or down a quarter pound). I suspect that screw will only be useful after the sear spring is bent such that it barely passes the flick test when the adjusting screw is backed all the way out to the stop. Then that screw should be able to successfully add to the trigger pull weight by screwing it in.

Time to start "adjusting" the sear spring itself.

Thanks to everyone for the suggestions,
Dave
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Old 11-15-2018, 05:06 PM
aprilian
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That screw only adjusts pull weight if the long spring leg is located inside the hollow screw. Is that how yours is set up?
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Old 11-16-2018, 10:58 AM
rdas
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That screw only adjusts pull weight if the long spring leg is located inside the hollow screw. Is that how yours is set up?
I think you meant "short leg", not "long leg", but yes, I'm using a stock sear spring in the non-flipped orientation, with the factory bent-up tip on the short rear leg, and the tip of the rear leg is in the "cup" in the end of the sear spring adjusting screw, and the long front leg is in the V-notch in the bottom of the sear.

I think the basic issue is how the sear spring adjusting screw works. It assumes that by turning the screw in more, the sear spring will apply more force to the sear with the other leg of the spring, or, conversely, apply less force if you back the screw out. But, if the spring is already well-compressed when the screw is backed all the way out, the spring is already applying close to its maximum force, so turning the adjusting screw in from there does no good (which is what I'm seeing). Ideally, it would just barely function reliably with the screw backed all the way out to the stop pin, giving the lightest practical trigger pull weight, and would apply the max force of the spring when screwed all the way in, giving the heaviest trigger pull weight you can get from that spring.

If you look at this photo, comparing various Buckmark sear springs, I think I want my sear spring from this gun (second from left) to look more like the silhouette sear spring (third from left), with the short rear leg coming off the coils a bit further down (with a non-flipped installation, down is to the left in that photo).

My goal is about 2.25lbs trigger pull weight (CMP rule 4.2.6 (e) allows 2.0 lbs minimum for a 22 rimfire pistol). I'm hoping the adjusting screw will help me to dial that in, once I get the sear spring close to that number.

Dave

Last edited by rdas; 11-16-2018 at 11:08 AM. Reason: Added link to photo
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Old 11-16-2018, 11:55 AM
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Originally Posted by rdas View Post


The photo below is of the disconnector, specifically the top of the disconnector hump. Again, the shiny spot, pointed to by the arrow, is where the disconnector is contacting the slide.
http://guns.dsttr.com/img/HeavyTrigg...111_013542.jpg
Dave
It appears to me the sear spring is upside down in the photo. The long leg of the sear spring should be originating from the bottom left. I have had better success in adjusting the sear spring to a specific lb.s of pull by unwinding the spring, testing, do it again, until your desired pull weight is achieved.

The simple way to place the sear spring back in place in insert the sear spring first, then insert the sear down on top of the long leg, led in the sear notch, and press down, hold and insert the sear pin. Very easy.

VH
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