Once upon a time I bought a new CZ Scorpion carbine (with the muzzle brake). One of the first things that I did was to measure the trigger pull. This was done before cleaning or lubricating the weapon in any way. The result was an average trigger pull weight, after 10 test pulls, of 9.63 pounds. [#1] Ouch.
Then I cleaned and lubricated the weapon and tested again. [#2]
Then I took it to the range for a 300 round break in and tested it again. [#3]
Then I cleaned and lubricated the weapon, post range trip, and tested it again. [#4]
Then I did a light polish of the trigger group parts and tested again. [#5]
Then I did a light file job on the trigger group parts, followed by another light polish, and tested yet again. [#6]
Finally, I installed the HBI spring kit and tested it one last time. [#7]
Whew! And here are the results.
#1 9.63 pounds
#2 9.10 pounds
#3 8.62 pounds
#4 8.26 pounds
#5 7.98 pounds
#6 7.38 pounds
#7 4.66 pounds
In theory installing an HBI Delta trigger will reduce the trigger pull by up to an additional 12%, but I was unable to verify this because my trigger pull tester self-centers on the trigger being tested. Since the Delta trigger is at a steeper angle than the stock trigger the tester self-centers higher on the Delta trigger and actually produces higher values, not lower. Since the point on the trigger should be where your finger rests, or at least on the same relative location on all tested triggers, this makes using the normal testing procedure invalid.
Changing the angle of pull during the test so that the contact point of the tester is on the same relative location on all tested triggers is one option, but may not be valid, either. I tried this with mixed results.
Another fix would be to set up a block either on the trigger or some other way so that the location of the contact point on the trigger is consistent between triggers and also maintains the correct pull angle. (I test with the pull angle parallel with axis of the barrel bore.) However, I was not able to setup such a block that I thought was truly valid, but I did the test anyway. The results were not, as I had suspected, valid.
Bottom line on the Delta trigger is that I think it makes an improvement in the trigger pull weight via an increase in leverage, but I can't really prove it.
Finally, I did a medium to heavy file/grind/polish trigger job, followed by a full lubrication, which now yields something less than a 4.5 pound trigger pull with the Delta trigger. That's using a standard test without any correction methods applied. I suspect that if I could do a valid corrected test I would see a final trigger pull weight of just over 4 pounds.
Yes, that was a lot of work. Thank you.
