redlightrich
New member
Hello all, in an effort to tune my CZ PCR with Kadet 22lr kit, I am forced to ponder coil springs and their effect, and how they respond to modification, specifically clipping off coils.
I have recently been working to make this pistol feed CCI SV40g ammo reliably. It becomes clear that the SV ammo doesn't have the power to fully cycle the slide.
This kit runs 100% with HV ammo of any brand I tested, which is about 10 different types. Due to the fact that many of my other guns run CCI SV, it is a big plus for me to get this to run it also.
My first attempt was cutting 2 coils off the recoil spring. It is a 2 dollar part, and easily corrected if I go too far. Cutting the 2 coils had no appreciable positive effect.
I then installed a 17# hammer spring ( on a CZ compact, factory is 19#), which made it better, but not perfect. It appears that the slide still "short strokes". I have carefully polished all slide contact areas, which made the gun smooth. The polishing was actually the first item I did. The 17# hammer spring has a second benefit of lowering the SA pull a bit.
As I read on the subject, I came across a person who stated cutting coil type spring coils actually raises the rate of the spring? They claim although you are lowering the pre-load on the spring, you are giving the spring a shorter amount of room to compress, which serves to raise it's value? I felt that this statement was a bunch of hooey, but it did give me pause.
This is in regards to my next moves. Do I continue to cut the recoil spring?
I also feel as if I keep lowering the hammer spring rate, I will eventually need to lower the firing pin spring weight as well.
I have just lowered the hammer spring again today to 16#, and will test for reliable ignition and cycling. I also have a 15# standing by, if the 16 has reliable ignition, but I still find short stroke.
Based on the fact that if I load the magazine with 5 rounds ( 10 round mags) I get nearly 100% cycling, I feel that I can get it to run right with more spring tweaking.
As I said, HV ammo cycles perfectly with stock springs. I am trying for perfection when using CCI SV ammo. I also don't want to give up the ability to use HV ammo as well. I need a perfect balance.
If I lower the hammer spring too much, my remedy ( at least as far as I know) is only to play with the firing pin spring. There is no extended FP available, although a lathe could make the pin move further forward.
Reshaping of the pin is always a possibility if cycling clears up, but positive ignition falls off.
Thank you for reading my long winded message which is actually asking " What says ye the experts? Is cutting coils as a way to decrease a springs strength an acceptable method?"
Also, where is there a chart that gives approximate spring strength based on wire diameter, coil diameter and free length? Or is this not enough info to find a value?
Thank you all
Rich
I have recently been working to make this pistol feed CCI SV40g ammo reliably. It becomes clear that the SV ammo doesn't have the power to fully cycle the slide.
This kit runs 100% with HV ammo of any brand I tested, which is about 10 different types. Due to the fact that many of my other guns run CCI SV, it is a big plus for me to get this to run it also.
My first attempt was cutting 2 coils off the recoil spring. It is a 2 dollar part, and easily corrected if I go too far. Cutting the 2 coils had no appreciable positive effect.
I then installed a 17# hammer spring ( on a CZ compact, factory is 19#), which made it better, but not perfect. It appears that the slide still "short strokes". I have carefully polished all slide contact areas, which made the gun smooth. The polishing was actually the first item I did. The 17# hammer spring has a second benefit of lowering the SA pull a bit.
As I read on the subject, I came across a person who stated cutting coil type spring coils actually raises the rate of the spring? They claim although you are lowering the pre-load on the spring, you are giving the spring a shorter amount of room to compress, which serves to raise it's value? I felt that this statement was a bunch of hooey, but it did give me pause.
This is in regards to my next moves. Do I continue to cut the recoil spring?
I also feel as if I keep lowering the hammer spring rate, I will eventually need to lower the firing pin spring weight as well.
I have just lowered the hammer spring again today to 16#, and will test for reliable ignition and cycling. I also have a 15# standing by, if the 16 has reliable ignition, but I still find short stroke.
Based on the fact that if I load the magazine with 5 rounds ( 10 round mags) I get nearly 100% cycling, I feel that I can get it to run right with more spring tweaking.
As I said, HV ammo cycles perfectly with stock springs. I am trying for perfection when using CCI SV ammo. I also don't want to give up the ability to use HV ammo as well. I need a perfect balance.
If I lower the hammer spring too much, my remedy ( at least as far as I know) is only to play with the firing pin spring. There is no extended FP available, although a lathe could make the pin move further forward.
Reshaping of the pin is always a possibility if cycling clears up, but positive ignition falls off.
Thank you for reading my long winded message which is actually asking " What says ye the experts? Is cutting coils as a way to decrease a springs strength an acceptable method?"
Also, where is there a chart that gives approximate spring strength based on wire diameter, coil diameter and free length? Or is this not enough info to find a value?
Thank you all
Rich