Slide Binding with Rook Rear Rails

RobKap

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I completed a PF940v2 (G17) frame. This is an 80% frame. I was intending to use Rook rails in the rear with the P80 front locking block/rail. I put it all together and the slide was binding so badly it would not slide on the frame past the trigger housing. I tried another slide with the same result of binding and not going on the frame fully. I then put the rook rails in a different, well functioning PF940v2 frame and had the same binding in that other frame with both slides. I tried a second set of Rook rear rails and had the same result - binding with both slides.

I then swapped the Rook rear rails with a P80 rear rail out of a working PF940c (G19) build. The Rook rear rails worked perfectly in the 940c frame. I put the P80 rear rail into the 940v2 frame and the slide went right on the frame. The slide was still not silky smooth but it seemed acceptably smooth with the P80 rear rail and P80 front locking block.

I took the new build to the range. After about 10 rounds, the slide started binding again (still using P80 rails front and back) to the point of producing failures to fully cycle. I added more oil and kept shooting/clearing malfunction/shooting. Somewhere around 40 rounds in, it started working and now functions without problem. I put about 150 rounds total through the gun with zero malfunctions through the last 110 rounds. The slide is now smooth on the rails.

I have used Rook rear rails a number of times before on 940c builds without issue. The only thing I could think of was some kind of misalignment between the Rook rear rail and the P80 locking block. I am not sure that I have previously used Rook rear rails in a 940v2 frame. I did build a CL with Rook rear rails and a Rook front locking block that worked without issue with standard G17 slides.

I am not really sure what happened here. I have enough experience with these builds to be competent with the basic challenges. I suspect some sort of issue with the P80 front locking block being a little bit out of spec. I have not had prior difficulty with the P80 locking blocks and/or Rook rear rails. Has anyone else had trouble using Rook rails with the P80 front locking block in a 940v2 frame?

Thanks,

Rob
 
Did you try putting the slide on the frame with JUST the rails? No other parts?

I'm not so sure it's the rails.
 
Make sure the rails are level to both the frame and each other and the slide flows freely with just the rails in the frame.
If not, decide why they're not level. If it is due to pin hole position, correct that issue. If it's not pin hole position errors, consider trying to level sand the rails. See below.

I've had what you described happen due to a funky front locking block on a 940SC even though there were no issues with the pin holes as both the P80 locking block and Rook rails installed just fine with the pins going in an and out easily. The issue was a slide alignment with the slide doing a slight wheelie towards the business end of the gun. I had three slides that had issues with these rails.

The front P80 locking block was out of whack doing a slight upward tilt. It was very slight, but enough to cause issues on slides with tighter tolerances. Level sanding it both helped cure the issue and helped with the sear engagement. In my situation, most of the material removed by sanding was on the front locking block and not the rear rails. You can mark your rails and FLB with a black marker or coating to see the low and high points when sanding. It's similar to a checkcoat sanding on car bodywork. In fact, I would do just that. In my case, the front locking block was coated black already, so it was dang easy to gradually see the angle differences as I slowly sanded the high spot down. It took me about 20-30 minutes hand sanding it over running water in the sink.

There is one thing to note here comparing my situation to yours. The SC frames had a bad batch of front locking blocks early on in the production line and I'm not aware of any issues that happened with a G17/23 frame. But, that doesn't mean there weren't any. The problematic locking blocks for the SC frame were coated black and I learned this from the now-defunct MGB forum. And indeed, my problematic FLB was indeed black, but I showed a photo of it in the forum and folks said it was probably not one of the problematic locking blocks. But it was indeed an issue for me.

Once I sanded it level to the rear rails, the gun worked well. I had all the issues you described. Difficulty getting the slide on the frame and binding. Unlike yours, mine would go on initially, it was just tight. I did not try to fire the gun with the problematic rails. It may have cleared up by racking it or firing some rounds like you describe, but I fixed it first before firing it.

Photos of the side of the frame with the problematic slide and rear rails may be beneficial here if the photos are in focus and positioned correctly. Additional photos may also show other issues that could cause it. A photo of the sear coverage along with the side view of the frame and slide might also help, but the sear photo is hard to take without good lighting, and you need a rear inspection half back plate. When I level sanded my rails, the sear coverage improved from about 70-80% to almost 100% coverage. And indeed today, I just put another striker in that same frame and it is 100% coverage without doubt.

You'll note that the Rook rear rails are thicker along a wider path than the P80 rear rails. The P80 rails appear to be roll formed into a radius edge. This is why it may be sticking more with the Rook rails with more surface friction there.
 
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I don't have any advice on your your problem but I can share your frustration. My last and final build refuses to cooperate. I tried combinations of two brands of front rails and 3 brands of rear rails. Some combos, a little better, some worse. The rails were level and flat, the pins went in easier and more aligned than ever. With no other parts except the rails, the slide moves slicker than any other build. Some slides worked on this frame one in particular absolutely would not.

What I did notice is that the rails on a Glock and PSA Dagger are much thinner than anything supplied or available for the 80%s. I like tight and snug rails but that may not be the answer. Stacking tolerances made this one slide inoperable. The tops of the rails need to be flat and aligned but don't neglect the bottom of the rail, i.e. the thickness of the rail. I gained some ground on this build but thinning the rails on the bottom side. I determined this by using smaller diameter pins to allow the locking block to float up a little and it started to operate. Obviously, the pistol can't run this way but for diagnosis, this worked.

Still working on it. Build it in 30 minutes my ass. I have hours in this and it is still a single shot at best.
 
With no other parts except the rails, the slide moves slicker than any other build.
Then the problem isn't the rails.

Still working on it. Build it in 30 minutes my ass. I have hours in this and it is still a single shot at best.
LOL! Yeah... that anti-2A media and politicians' claim chaps my ass, too. First of all, the time it takes is irrelevant to whether it falls under our Rights as protected by the 2nd Amendment. It doesn't matter if it takes 30 minutes or 30 hours. Nevertheless, the claim that "It takes only 30 minutes by an untrained person" is bullshit.

I think I spent 30 - 40 hours on my first build. But, I'm a perfectionist and very detail-oriented. I watched every MGB video, too. And that's likely why my first build has never had a malfunction from the first round fired to the 2,240th. And that's why my P80 builds collectively have 13,000 rounds fired successfully.

Mind you, it doesn't take me 30 hours anymore. But it's still several hours. Just the RSA channel takes me a couple of hours, still. But then they look like this:
PGB-channel-and-rails.jpg


FWIW, all of my builds use Rook Tactical rails. I've never had to adjust or level any of them.
 
Make sure the rails are level to both the frame and each other and the slide flows freely with just the rails in the frame.
If not, decide why they're not level. If it is due to pin hole position, correct that issue. If it's not pin hole position errors, consider trying to level sand the rails. See below.

I've had what you described happen due to a funky front locking block on a 940SC even though there were no issues with the pin holes as both the P80 locking block and Rook rails installed just fine with the pins going in an and out easily. The issue was a slide alignment with the slide doing a slight wheelie towards the business end of the gun. I had three slides that had issues with these rails.

The front P80 locking block was out of whack doing a slight upward tilt. It was very slight, but enough to cause issues on slides with tighter tolerances. Level sanding it both helped cure the issue and helped with the sear engagement. In my situation, most of the material removed by sanding was on the front locking block and not the rear rails. You can mark your rails and FLB with a black marker or coating to see the low and high points when sanding. It's similar to a checkcoat sanding on car bodywork. In fact, I would do just that. In my case, the front locking block was coated black already, so it was dang easy to gradually see the angle differences as I slowly sanded the high spot down. It took me about 20-30 minutes hand sanding it over running water in the sink.

There is one thing to note here comparing my situation to yours. The SC frames had a bad batch of front locking blocks early on in the production line and I'm not aware of any issues that happened with a G17/23 frame. But, that doesn't mean there weren't any. The problematic locking blocks for the SC frame were coated black and I learned this from the now-defunct MGB forum. And indeed, my problematic FLB was indeed black, but I showed a photo of it in the forum and folks said it was probably not one of the problematic locking blocks. But it was indeed an issue for me.

Once I sanded it level to the rear rails, the gun worked well. I had all the issues you described. Difficulty getting the slide on the frame and binding. Unlike yours, mine would go on initially, it was just tight. I did not try to fire the gun with the problematic rails. It may have cleared up by racking it or firing some rounds like you describe, but I fixed it first before firing it.

Photos of the side of the frame with the problematic slide and rear rails may be beneficial here if the photos are in focus and positioned correctly. Additional photos may also show other issues that could cause it. A photo of the sear coverage along with the side view of the frame and slide might also help, but the sear photo is hard to take without good lighting, and you need a rear inspection half back plate. When I level sanded my rails, the sear coverage improved from about 70-80% to almost 100% coverage. And indeed today, I just put another striker in that same frame and it is 100% coverage without doubt.

You'll note that the Rook rear rails are thicker along a wider path than the P80 rear rails. The P80 rails appear to be roll formed into a radius edge. This is why it may be sticking more with the Rook rails with more surface friction there.
I considered assembling the frame with just the rails to attempt level sanding but the two piece Rook rails require the trigger housing to install leaving the ejector sticking up above the rails. I am confident that the pin holes are drilled correctly. I experimented with two sets of Rook rear rails on a different 940v2 frame (swapping only the rear rails) and had the same binding issue. Both sets of Rook rear rails were purchased over a year ago from the same batch. I took some measurements with calipers and found the overall width of the Rook rails installed is almost exactly the same as the overall width of the P80 rear rails module. However, the Rook rails are more square at the front than the P80 rails which have a slight taper.
 
Then the problem isn't the rails.
That is correct. A combination of tolerance stacking is the problem. Basically, as I rack the slide, the barrel can't tilt down enough and it jams the slide when it is near the rear of travel. This slide and barrel will work on my Dagger frame. The rails on that are much thinner and more important, allows more movement upward of the slide. This gives enough clearance for barrel-slide-rail relationship to work.

In this case, the top of the rail is meaningless. The bottom side of the rail is the cause of my problems.

This particular slide has always been a problem child. I'm fixing it the old fashion way. Buying a different one. It is useful for testing purposes.
 
I considered assembling the frame with just the rails to attempt level sanding but the two piece Rook rails require the trigger housing to install leaving the ejector sticking up above the rails.
Aha. You're correct. I sanded the rails a decent while back and I forgot about including the step where chopped a trigger housing top after removing the ejector in order to level sand a frame with Rook rails. See photo.

If you do opt to level sand after checking for square, do not go further down than the top of the frame's plastic tabs that stick up. In my case, based on where my holes were drilled in the frame, I have sanded to about level with the top of the frame's plastic tabs and my sear coverage is right at 100% on several frames.

Also attached in the photo are inspection plates. It is interesting to see what happens when level sanding gradually to the sear and the plates allow you to see what is happening there relative to your sanding.

Build it in 30 minutes my ass. I have hours in this

And @bkbrno is correct about slide tolerances. I have a group of slides to test on the frames, and some are tighter than others.



trigger_housing_chopped.jpg
 
I have had to fit the barrel and front locking block a couple of times. A light touch with a file and some polishing.
 
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