XR9-S recoil spring?
"skeptics thought that fitting a recoil spring into this gun was impossible, there was actually a space for it, but in an unconventional location - along the lower-left corner of the barrel, allowing the spring working length to be virtually the full length of the gun"
I'm not sure I understand where the recoil spring is...a diagram would help, thanks.
Also, are there any other differences in the mechanism of the XR9-S versus XR9-F?
I'm not sure I understand where the recoil spring is...a diagram would help, thanks.
Also, are there any other differences in the mechanism of the XR9-S versus XR9-F?
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Replies to This Discussion
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Permalink Reply by VMole8 on -
You can see the guide rod at the shooter's 7:30 position to the barrel, in the "She Means Business" photo on the photo page. (I tried to link but I couldn't get it to work in the editor.)
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Permalink Reply by Arne Boberg on -
Here is a link to an image that shows the spring/guide rod location. From the shooter's perspective, it is at about the 7:30 position. http://www.bobergarms.com/photo/she-means-business?context=latest
The mechanisms in the XR9-S and XR9-L are identical. Only the length of the front end of the gun and a few other parts are different, and these parts inlcude the longer slide spring/guide rod.
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Permalink Reply by Arne Boberg on
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Here is another view showing where the slide spring is located: http://www.bobergarms.com/photo/underside-of-slide-assembly
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Permalink Reply by urbock on
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Arne,
This isn't intended as a criticism, just curiosity. What firearms engineering presidents, if any, are there for the asymmetrical recoil spring?
Arne Boberg said:Here is another view showing where the slide spring is located: http://www.bobergarms.com/photo/underside-of-slide-assembly
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Permalink Reply by VMole8 on
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I'm interested to hear Arne's comments too, but conceptually the only difference between a diagonal offset and a strictly vertical offset found in traditional pistols is the potential for some added friction on the left-side frame rail.
This would likely occur mainly during the return stroke since the recoil stroke will have a pretty strong, square momentum from the cartridge base applied to the breach face, while the return stroke will be primarily spring driven with the resulting left side bias. However, a couple things with this design should minimize any undue wear: One being the generous "rail-estate" compared to, say, a Glock with its tiny (albeit steel) inserts; another being the likely follow-on of the very wide hammer which would tend to provide a squaring force, closer to battery, against the firing pin assembly block (assuming the hammer keeps up with the slide); further, the slide's recoil lug/"bib" (filling the gap below the muzzle in front) may have sufficiently tight clearances between the walls of the frame/dust-cover to share some horizontal friction load, but that is also speculation on my part.
Normally, the recoil spring exerts a balanced lifting force on the slide which focuses wear evenly, left and right, on the underside of the frame rails toward the front and the top of the frame rails in the back. The XR9's 7:30 spring position should simply spread a little of that friction to the outside of the left frame rail, in actuality lessening the friction focused on other areas somewhat.
All said, though, the actual torque developed by the recoil spring should be quite small in any direction relative to other pistols because of how tightly the skinny spring and guide rod are tucked in along the bore/recoil axis as well as the relative lightness of the spring allowed by the rotating barrel lockup and hammer fired design. The total upward and sideways forces on the rails should be minuscule compared to most designs for these reasons, and I would expect the rail life to reflect that.
The grade and hard coat of the frame alloy is also very important, and forged 7075 T6 as used in this pistol is as good as you'll find. It's the same as used in military-issue M-16/M-4 receivers by Colt, FN, & LMT, which incidentally also endure steel-to-alloy friction for a long, long time.
Just keep the rails lubed with a film of quality gun grease like Slip2000, as you should anyway, and the last thing you'll need to worry about are any side effects of the positioning of the recoil spring.
Perhaps my comments will provide an easy template for Arne to add/clarify/correct.
Hope that helps.
Cheers.
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Permalink Reply by Out of curiosity on
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I was also concerned with the asymmetrical spring location (thinking that one on each side would do better), but if the gun works well this way then that's ok for me...once again, only an intensive +P torture test (with no cleaning, no oiling taking place) could prove reliability of the mechanism.
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Permalink Reply by Arne Boberg on
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VMole9 said:
"All said, though, the actual torque developed by the recoil spring should be quite small in any direction relative to other pistols because of how tightly the skinny spring and guide rod are tucked in along the bore/recoil axis as well as the relative lightness of the spring allowed by the rotating barrel lockup and hammer fired design. The total upward and sideways forces on the rails should be minuscule compared to most designs for these reasons, and I would expect the rail life to reflect that."
I couldn't have put it better myself. When you think about it, our recoil spring is much lighter than other recoil springs and it is very close to the bore axis, so the torque is indeed minimal. The fact that this torque is from the left side, however small, is really only seen by the frame on the return stroke, and the force of the hammer does indeed even it out a bit. The offset recoil spring does in no way affect reliability, and after thousands of rounds, has had no affect on durability of the frame (or the spring). I believe that the Desert Eagle uses two such springs because it needs the extra force.
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Permalink Reply by Out of curiosity on
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I have another question about pistol mechanism. It has been said that the cartridge is under permanent control from the time it is taken out of the magazine to the time it is loaded into the chamber, due to tongs that keep a firm grip on it the all time long, therefore avoiding any risk of feeding failure.
However, as I was watching at the XR9 mechanism video, I noticed that when the slide reach maximum draw back position (at this point the cartridge is aligned with the chamber, but still far away from it) , the tongs are no longer holding the cartridge anymore, while the cartridge is not yet entering the chamber: it looks like at this point, the cartridge is free of any control and could go into a nose dive (looks like cartridge might point nose down down into the the magazine direction, possibly missing the chamber mouth and blocking the mechanism).
I guess there is something that is keeping the cartridge under control that isn't apparent in the video, could you quickly explain it? Thanks
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Permalink Reply by VMole8 on
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Out of curiosity said:I have another question about pistol mechanism. It has been said that the cartridge is under permanent control from the time it is taken out of the magazine to the time it is loaded into the chamber, due to tongs that keep a firm grip on it the all time long, therefore avoiding any risk of feeding failure.
However, as I was watching at the XR9 mechanism video, I noticed that when the slide reach maximum draw back position, the tongs are no longer holding the cartridge anymore, while the cartridge is not yet entering the chamber: it looks like at this point, the cartridge is free of any control and could go into a nose dive (falling nose down back into the the magazine direction, possibly missing the chamber mouth).
I guess there is something that is keeping the cartridge under control that isn't apparent in the video, could you quickly explain it? Thanks
From the description, the design operates like most pistols in the sense that once the case base is lifted in line with the bore axis, the case rim has slid under the extractor hook on the right side and is pressed against a lug/wall on the left side of the breech face, thus holding the cartridge in control through the forward stroke. Apparently the Boberg mechanism has an actual extractor hook on the left side as well, instead of a simple lug, in order to ensure certain extraction and greater control during loading. If you try with most properly tuned pistols, you can slide a cartridge into position on an open breech and it will stay there protruding in space.
I am curious, though, how the left-side extractor behaves at the moment of ejection. Does it spring out of the way or... ?
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Permalink Reply by Arne Boberg on
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The left side extractor is fixed relative to the slide. Its "hook" is a 45-degree ledge, so the ejector can overcome it.
As far as the rearward position of the slide is concerned - it is true that the Tongs will hand off the cartridge to the breech area, where the dual extractors are waiting. Through this transition there is no point where the case flange is "free". There is case-flange overlap with the Tongs and the right-side (spring-loaded) extractor.
As far as cartridge "nose diving" is concerned - it can't do this since the lifing ramp is in the way. When the slide moves forward, and the lifting ramp starts moving back down, the dual extractors now have control over the cartridge via the case flange and deliver it straight in to the chamber.
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Permalink Reply by Blueorison on -
And thus, Watson, you have brilliant mechanics at work.
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Permalink Reply by elsullo on
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Think of the M1 Carbine: the location of the single recoil spring does not matter since the frame guides the slide and torque is minimal..............................elsullo
urbock said:Arne,
This isn't intended as a criticism, just curiosity. What firearms engineering presidents, if any, are there for the asymmetrical recoil spring?
Arne Boberg said:Here is another view showing where the slide spring is located: http://www.bobergarms.com/photo/underside-of-slide-assembly
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