Spring tuning for pistols

[BCRider]

I'm curious about my new gun and how the whole practice of selecting the springs works for fine tuning. My goal is to work the DA effort down a bit for that first shot in IPSC and just for general feel when shooting.

Now I may be wrong here but this is how my thought process is working. Please bear with me as I'm totally new to firearms but have done a lot of mechanical work over my life so I THINK I'm pretty decent at analyzing systems as long as I know I've taken all the factors into account. I'm just not sure that I've identified all the factors in this case.

I'll make this a list so it's easy for you folks that know this stuff to confirm or correct me.

1. During a cycle the slide pushes back against both the recoil spring directly AND the mainspring via the hammer to recock the hammer. So it is actually compressing both springs at the same time. Is that right?
2. Now the goal of the main/hammer spring is to store enough energy to ensure a consistent firing of the primer. However we want to keep the mainspring as light as possible to reduce the DA efforts for that first shot, right?
3. So if this is all correct so far then the procedure for lightening the DA pull is to reduce the mainspring rate until you start getting the odd FTF and then go back to the last consistent firing spring or possibly shim the lower pressure spring to add in a little preload until it fires consistently?
4. With the hammer working nicely now attention can be focused on the recoil spring. Again correct me please if I'm not analyzing this correctly. The recoil action needs to do three things. It needs to cycle back far enough to recock the hammer. It also needs to cycle far enough back to ensure a clean ejection. And finally it needs to be strong enough to force the slide forward while stripping the next round from the magazine and up into the breech. If the spring is too hard it may not cycle back far enough to ensure the ejection. But if it is too soft it'll hit too hard at the end of the rearward travel. And if really soft it may not cleanly strip the next round out of the breech with enough force to ensure it positively loads the round. And I'm going to assume here that it is better to slightly bounce off the rear travel limit than to not cycle the full distance? But you don't want it to slam the travel limit or it'll kick the gun around too much. So I would want to work with the hardest spring first (presumably stock factory?) and work down until I do not get any stove pipes but I feel the least kicking?

Sorry if I've packed a lot into this but I'm like a kid with a new toy and want it to work as best as I can. Also being new to semi automatic pistols I'm trying to learn how they operate all at the same time.

I had the pleasure of shooting a Shadow that had been fine tuned and while my new Shadow is still a pleasure I'm really looking forward to doing a similar tuning job on my own gun. Especially in the case of the DA issue and the fact that I've had three stovepipes in my first 300 rounds through the gun the other day. I know that some of this is also related to just getting some rounds through the beast to help it break in but I'm guessing that I'll want to be doing the spring job sooner or later.

 

[mattewyingchen]

I am looking forward to any answers to your post too. I am basically in the same situation as you and always thinking about changing the recoil spring to a softer one to fix a stovepiping problem with my cz 75.

 

[BCRider]

46 views and no one has an opinion? Or even a comment about being at least on the right track or out in left field?

 

[tommyg]

what pistol

46 views and no one has an opinion? Or even a comment about being at least on the right track or out in left field?

first off what make and model of pistol???

On a DA first shot pistol the first trigger pull the trigger operates the hammer, hammer spring, sear and some sort of sear return spring or sear disconnnector. So to lighten the first trigger pull weight can impact on the actions ability to only fire in semi auto or fire at all. On a revolver even slight reduction in hammer spring tension will cause misfires. only experienced gunsmiths should be given this task( or switch to a 1911 type, or a pistol that has a SA first shot option)
Then the recoil spring can be tuned for your slide inertia/ hammer spring/ load power. realizing that a factory spring is a compromise that is made to handle a wide range of possible loads. If you are going to use a major load and try to use a lighter recoil spring be sure to use a recoil buffer to lessen the peening / work hardening effect of the slide on the frame.

 

[BCRider]

Well it's my new CZ Shadow. But I was thinking more in general practices on spring selection. I'm more interested in how the main and recoil springs work together in general terms so I can understand more about the operation of semi auto pistols at this piont

It's not that I want to use a lighter spring just for the case of using a lighter spring. I'm far more into looking for the optimum spring for each case and what to look for to help pick the best option.

You raise an interesting point about the load power though. I new enough that I hadn't thought about how it all interplays but I can see that the recoil spring would be best chosen to work with the load being used such that the slide comes back far and fast enough but I'd probably want to limit the power it slams into the stops on the frame. Sounds like a case of choosing the recoil spring to suit the round used most frequently.

 

[tommyg]

springs

Well it's my new CZ Shadow. But I was thinking more in general practices on spring selection. I'm more interested in how the main and recoil springs work together in general terms so I can understand more about the operation of semi auto pistols at this piont

While it may seem like the hammer spring adds extra pressure to the slide during recoil, in reality it only provides enough energy to ensure a solid primer strike, you can see this by the amount of force required to compress each spring, one can easily compress the hammer spring with one thumb, but the recoil spring takes multiple times the force to compress.

additionally the slide does not act on the hammer directly but rather angularly. As the slide moves rearward the amount of force counteracting the slides movement decreases significantly as the hammer is laid back and held by the sear. It is the recoil spring that resists 99.9% of the slides movement after the locking lugs unlock.

try think about the operation from sear release, to return to battery, as single discrete motions that are sequential (ie no actions occur coincidentally)
like this

trigger moves full rearward
sear moves
hammer hits firing pin
pin hits primer
primer explodes
powder burns
bullet forced down barrel
bullet leaves barrel
locking lugs release
slide moves back
hammer reset/ sear engaged
slide returns to battery
trigger released/ reset

hope that helps

tg

 

[BCRider]

That does. Thanks.

At the moment it's more about the DA pull for that mandated first shot in IPSC and, I assume, with IDPA as well. What extra points would be inserted into that list to include the DA operation?

And in DA mode it's my finger compressing the trigger spring via the trigger and internal levers to move the hammer back. Now that is where I'll feel the resistance from two factors as I see it. First is obviously the hammer spring resistance and second would be any minor roughness in the interaction of the parts that relay the force from the trigger to the hammer to compress that spring.

 

[tommyg]

ww w.czub.cz/index.php?p=32&idp=1&ids=3&idz=208&lang=en

go to this page and click on the spare parts pdf it will show you how interaction of the trigger/ trigger bar/ sear / disconnector /hammer spring works

essentially if you lighten the hammer spring the primer might not go off, it can be done but a qualified 'smith should do the work.

 

[relliott]

The mainsprings primary function is to ignite the primer and fire the round. They can be adjusted to (slightly)reduce the amount of pressure brought against the sear, and thus reduce the S/A pull weight, but there's not a lot of mileage in this. Most people wouldn't notice the difference though if the sear is mated correctly with the hammer hooks. Using different weight mainsprings can also adjust the guns timing slightly, in that a heavier spring can delay the slide unlocking for just an instant longer after the round is ignited. This kind of tuning would be more likely to be noticed in Open guns than Production guns.

You can indeed also use lighter springs to lighten the D/A pull, but the lighter you go the narrower your window of reliability becomes. You'll end up likely having to tune the spring to a specific primer brand. In Divisions other than Production, a lightened mainspring is usually accompanied by an extended firing pin. Not legal for Production. I wouldn't go with anything greater than a pound or two lighter. Beyond that and you'll be double-stroking unfired rounds in matches while the clock is ticking.

A light D/A pull is nice, but in my opinion a SMOOTH pull is way more important. If you can polish out all of the tool marks and smooth out the friction points, then lube them correctly, you will get much better consistency in your first shot acquisitions. A notchy, draggy trigger is very hard to hit consistently with.

Good luck.

R

 

[BCRider]

Thanks for the link Tommy. And thanks for the info R.

I'm no stranger to metal working and with the guides they have on a CZ specific website I have no qualms about smoothing the DA contact points to smoothen the pull.

The SA pull is already light enough for me. The Shadow comes with a comp hammer that seems to have a lot less walk back (or whatever it's called) that pushes the hammer back as you pull the trigger so the SA pull is delightfully light as it comes. No changes there for me. It's the DA pull that seems to feel a little like it's pulling a plow through gravel and feels a bit heavy. Especially after having shot the other guy's Shadow that has had the trigger job done to it.

Anyhow I thank both of you for the links and explanations. It's oddly enough not that easy to find such info out there about all the aspects of the firing and recocking cycle. Or I'm just not using the right search terms.

 

[monkeycanada]

I think everybody is missing the point, DA on semi-auto pistol are designed to be stiff for safety. And yes most DA semi-autos and be made liter with no ill effect to the gun. I have done it loads of time and yes its a combination of spring pressure and friction reduction and correct sear and cam angles, etc.

 

[BCRider]

Thanks mc. And yes, since this is intended for IPSC production there's no need for carry safety issues with respect to a hard DA pull for safety's sake.