I think it could mostly be attributed to tolerance stacking. They said the whole that the sear spring seats in was bored a little deeper then normal. This of course was a non issue with the oem spring, but it became an issue with their spring. So they had to install just a slightly longer spring to hold the correct amount of pressure on the sear.
They had fantastic customer service, although my Yankee ears struggled a little with the cajun accent lol.
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