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Discussion Starter · #1 ·
Ok, in recent days more discussion has brought up the use of lighter springs in the XD and others have sworn by heavier springs. I was thinking about this last night trying to logic out the mechanical advantages of each method. Just by my own noodling I thought up the following:

Lighter Spring (stock #18 to #16):
Essentially what you are doing here is removing 11.11% of the resistance to slide return. This does two things. First, it reduces the spring force on the frame assembly. But then I started thinking about slide slam. I would stand to reason that if you are reducing the pressure of the slide resistance by more than 10%, you are going to increase the force with which the slide impacts the frame. Wouldnt this cause a shock recoil via the frame into your stance? Thus one would think the recoil to be a lighter resistance and more of a sharp recoil.

Heavier Spring (stock #18 to #20 or #22):
This time you are adding that same 11.11% of the resistance to slide return. This should slow down the slide to frame impact and also decrease the overall rate of return on the slide. One would think, however that you would also have an increased pressure on the frame assembly, after all that is, ultimately, the resistor for the spring to press against when it is compressed by a slide blowback.

Am I way off base? Remember, this is all just me trying to apply what I know about physics of a recoil and the structure of the XD in my mind so I could be way wrong, I dont mind people pointing out where im screwing up. IF the above is true, then it would follow that making the choice in whether to go lighter or heavier is a personal decision of what you would like to do with the recoil. Would you like to go lighter and instead of getting a full blow back, you get a short sharp recoil? Or would you rather go heavier and have the spring eat a bit of it and then have more of the recoil forced straight-back against the frame.
 

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Go to www.customglockracing.com. Theres a great article entitled "spring wars", you can find this under "tech & maintenance". Basically, you can only alter the timing of the recoil impulse by changing springs. It's a very subjective thing. I do suggest checking the slide for full travel, anytime you switch to an aftermarket setup. In the past, I've had after market springs that "crashed" before the slide could reach its rear stop, this can have an adverse effect on reliability. Good advice is to never go more than 2-3 lbs. over or under the factory spec spring.
 

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Re: Your comment on heavy springs:

wfrazee said:
This should slow down the slide to frame impact and also decrease the overall rate of return on the slide.
Looks good - However, maybe by "return" you mean "recoil" - With a heavier spring, my slide is harder to pull back, and thus returns to the front of the slide with more force/speed than a lighter spring. (I use a 22# spring.)

The reason I use a heavier spring is to reduce the snap at the end of the recoil. But now I'm starting to rethink the whole subject because I want to go back to captured-spring guide rod, and make the slide racking easier on my collective familie's wrists.

-Mike
 

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Discussion Starter · #5 ·
mcone said:
Re: Your comment on heavy springs:

wfrazee said:
This should slow down the slide to frame impact and also decrease the overall rate of return on the slide.
Looks good - However, maybe by "return" you mean "recoil" - With a heavier spring, my slide is harder to pull back, and thus returns to the front of the slide with more force/speed than a lighter spring. (I use a 22# spring.)
Correct, I was referring to the rate of return AT the shooter against the spring pressure. Although you are correct in that technically the return action in that mechanism should be the return to battery.
 

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You are correct in your assesment. For me, I prefer a flat recoiling gun (light spring) because it does not upset my stance and my sights come back to the target much quicker. I have tried both ways and I personaly prefer a fast slide and a bit of flip over a spring that raises both my hands and ruins my sight picture.
 

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Great post,
I think it does come down to personal prference, and I agree with ichy that I like a flat shooting gun also. I'm sure that for most people thet use an XD for self defence the 20#+ is the way to go for 100%reliability. I left the factory spring in my service modle, and it's 100% every time I pull the trigger.

I shot 1911 type guns in USPSA matches for about 10 years, and once I got to the point that I could see the front sight throught the recoil impulse I learned that the lighter the spring I used the less the slide dipped. I was using a 13 or 14# spring in my STI, and the sights would come right back into the A zone if my grip was right.

With my XD40 Tactical I put a 16# spring in it and I like the way the sight tracks, but it looks like I'm going to have to go with a 18# spring to make it more reliable.
 

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I love math and physics and this is a tough one for me to figure out and model. A big variable is the grip strength and how that effects what happens. I have considered mounting accelerometers to my slide, and I am even more motivated now. The results will not be definative on what is best (that will vary with each and every shooter) but it should give us a profile of what the forces are during recoil. I see what I can do this weekend to create the mount, then bother my bud with the digital oscilloscope to capture the traces.

Hmmmm.... :?: :!: :idea:
 

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Tonight I fabbed up a steel dovetail piece with a couple of 4-40 threaded holes. That only gives me a couple of threads worth of engagement to mount my accelerometer block, but I think it will be ok.
Under the front sight there is a hole centered on the slide. Any ideas of what it is for? I might thread it to help stiffen up my mount. Roughly 0.098" diameter thru hole, just begging for 4-40 threads with better thread engagement.
 

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OK, off to a good start. Here are a couple of accelerometers mounted, it is a good stiff mount. It adds about 3oz to the slide, but since I am looking for relative info rather than absolute it should work. One accelerometer will measure along the axis of the slide, one is perpendicular measuring the muzzle lift.

The supporting cartridge is for another pistol.:wink:

 

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Is that thing legal. Think I saw one of those in 1969 in a head shop with a rubber hose attached to it and a peace sign etched on it. :shock:
 

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Discussion Starter · #15 ·
for a good measurement of force carryover, you need an accelerometer on the frame somewhere as well, to find out how far "back" the frame is forced.
 

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Don is that the new periscope sight I heard you were working on??
And how is the around the corner one coming?
 
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