How To Increase SAO Trigger Pull

[azdover]

I recently bought a steel P-01 manual safety.   Supposedly I'm the second owner.  According to the shop I got it from, the PO bought it new but never fired it, and then decided to sell it on consignment.   So it's probably factory stock.  DA pull measured 9.5# and SA 5# with the usual sear cage movement, trigger camming, and gritty trigger.

I've converted it to SAO by removing the disco and adding a dual adjustable flat face trigger.  Did the usual buff and fluff but didn't mess with hammer or sear geometry.  I was able to tighten up and limit a lot of the sear cage movement with the extended hammer pin retaining peg mod (long name for such a short part) and added a .010" brass shim to the right side of the sear cage.  There is now no noticeable sear cage hammer movement during the trigger pull.   There is still a slight bit of hammer camming and sear cage movement if the trigger is pulled with the safety engaged.  And I also spent half a hour looking for the lifter spring when it decided to take a tour of my work bench while trying to put everything back together.

Trigger pulled has smoothed out a lot and is now about 3.5#.  I want to get it back up into the 4.5 to 5# range.  So far it looks like my options are:
1.  Heavier Wolff hammer spring - 22, 24 or 26#
2.  Heavier trigger return spring
3.  Heavier lifter spring

Anybody have any other suggestions or experience with any of these set ups?  I've run a search, but all the info is on how to reduce trigger pull not increase it.

Any help would be greatly appreciated,
Pete

[timmy75]

4. heavier sear spring

[Earl Keese]

Hammer spring won't have much effect. Try bending the trigger return spring.

[tdogg]

You have almost all the options listed.  Since you are working with a firing pin block gun I don't think there is room to put two sear springs in it.  That is the another option I know of to increase pull weight. 

You can increase the pull by about 1/4 lb by using a Tanfoglio sear spring.
You can increase the pull by about 1/4 lb by using a 26lb main spring.

My numbers are with a TSO so they will actually probably be higher on your P01 due to the stock hammer and hammer camming.

Chronicled here:  https://czfirearms.us/index.php?topic=86250.msg645137#msg645137

I'd start with a heavier trigger return spring and see where you end up.  If you needed more I would install the heavier lifter spring.  I willing to bet the heavy trigger return spring gets you the 4.5lb trigger pull.

Cheers,
Toby

[Tok36]

   Last time i tried it, a Tanfog Sear Spring would not fit into an unmodified CZ 75 variant decocker sear cage do to the added spring coil. While i did not attempt to modify the sear cage parts to add space for the Tanfog Sear Spring, it did look doable with the correct modification. They have dropped right into the safety models for me though.

   CZ Customs offers a CZ Custom Carry / Duty hammer, though i am unclear how this compares with a CZ factory Hammer. "Gives slightly heavier  trigger weight of the single action release. For best results pair with our Heavy Trigger Return Spring (#10215)"

CZ Custom Carry / Duty hammer
https://czcustom.com/cz-parts-all/hammers/czc-4lb-hammer.html

[azdover]

Thanks for the suggestions, especially the heavier sear spring.  Time to apply some plastic to the situation to order some parts and then get out some of my favorite tools and get to work.
Pete

[azdover]

Finally got a CZC heavy trigger return spring and a CGW heavy lifter spring.  With both installed, trigger pull increased to 6 lbs - a little heavy for my tastes.  Removing the lifter spring with only the trigger return spring gave me a pull of 5 lb plus some change.

So in my particular situation, a heavy trigger return gave me a 1.5 lb increase in trigger pull on my P-01 SAO conversion without affecting trigger feel.

[azdover]

Hammer spring won't have much effect. Try bending the trigger return spring.

The CZC heavy TRS still increases the trigger pull a little too much for me even without the heavy lifter spring.  The picture below shows - top to bottom - a heavy TRS before installation, a heavy TRS after install, and the original P-01 TRS.  The CZC heavy TRS uses noticeably a thicker spring compared to the original.   Installing it was like arm wresting an octopus.  It takes a set after install, developing a 45 degree angle between its legs.

Taking Earl's advice to bend the TRS legs, I increased the leg angle to 60 degrees by twisting the 2 legs further apart to effectively tighten the TRS coil while relieving some of the tension between the trigger and the frame.  The trigger pull is now 4.5 lbs when measured in the middle of the flat faced trigger with a digital gauge.  Feel and reset are still unaffected.

I probably should have taken Earl's advice from the gitgo and bent the original TRS.   Decreasing the leg angle on the factory TRS would increase the tension between the trigger and frame, effectively giving me the same effect as increasing the angle on the heavy TRS to decrease tension.  But unfortunatly, my reading comprehension is not the best.  At first I thought he was referring to the sear spring.

After messing with the TRS and lifter springs, it looks to me like the TRS has the most effect on trigger pull in my P-01 SAO conversion.