I've posted this before, until Jard releases their new trigger that retains the bolt lock feature, I will use the HVHA spring.
I have used the Yodave and Mcarbo springs in the past, the results were positive, but some triggers would not get to the low 2lb point I wanted. I have been impressed with the HVHA spring, they have been very consistent in pull weight from rifle to rifle. So much so, I have quit the other 4 offerings, GunBloke and Ernie's the Gunsmith were the other two. Ernie's were consistent, but because of a lack of sales, he quit offering them. I am not 100% positive, but I believe his were identical or very similar to the HVHA in looks and pull weight. I haven't had one in my hands in years and I think the only rifle/rifles I still have one in are the 30'06 at Browning and the 7mm-08 that I bought 15yrs ago. Don't get me wrong, both the MCarbo and Yodave are solid improvements and I have used dozens of each, I was just not able to get to the high 1lb low 2lb range without replacing the set screw to reduce it's length or trimming the spring. The latter method is no longer my method, I learned quite a bit from other members here about the fallacy of my trimming method in another thread. I was able to achieve the low pull weight, but only because I reduced the overall length of the screw and spring, not because I trimmed the spring.
@1mechanic @ntsqd both provided formulas and evidence to literally blow my mind and entire thought process on coil springs. I said I do everything wrong because I like setting an example, well, there's another example. If you want to read the evidence, here:
My idiocy on full display Go to page 2 where school is in session.
I bought set screws and a tap since they are metric and I made a fixture to face the bottom of set screw to shorten them and still have the interference as they are "tightened" and remain in place in the trigger. A lot of work I know, but I really appreciate the value of the trigger bolt release on safe feature.
I spoke to Jard over the summer and posted this on September 5th: