Upgrade kit to give match trigger performance with tighter and smoother pull, and a glass sharp break.\u00a0 Competition trigger performance on a combat rifle.\u00a0 Fits all SIG rifles in the 55x series, including the 550, 551, 553, 556 classic, 556R, and the latest 556XI revisions.\u00a0 It also fits the 751.\u00a0 I *think* it will also fit older 510, 543 and 547, though has not actually been done yet.<\/p>\n
Kit includes:<\/big><\/big><\/p>\n
New hammer, sear, and sear spring. \u00a0All parts are \u2018drop-in\u2019 with zero modifications.<\/p>\n
Key benefits:<\/big><\/big><\/p>\n
\u2013 A true 2-stage trigger.\u00a0 \u2018Pre-first stage slack\u2019 in original trigger is eliminated.<\/p>\n
\u2013 Exceptional butter smooth trigger pull with no gritty feel or break-in needed. \u00a0Hammer and sear are pre-polished for smoothness, and hard coated for low friction and durability.<\/p>\n
\u2013 Reliable performance, even in dirty conditions. \u00a0Grease is optional. \u00a0Hammer and sear have an advanced low friction surface coating that does not need lubrication,\u00a0which might attract dirt.<\/p>\n
\u2013 Hammer and sear are machined from billet plate tool steel (not cast), and full depth heat treated.\u00a0 High quality steel holds sharp sear edges that will \u2018break like glass\u2019.<\/p>\n
\u2013 Smoother feeding. \u00a0Low friction coating on hammer reduces hangup with bolt carrier.\u00a0 Latest XI modifications are included to make the \u2018hammer hang-up\u2019 issue disappear.<\/p>\n
\u2013 Long life. \u00a0Sear edges are oversized, reducing load, for years of match grade performance.<\/p>\n
\u2013 Installation by\u00a0gunsmith or armorer is recommended to adjust\u00a0second stage sear engagement (pressure plunger behind\u00a0trigger), but should take 20 minutes or less.<\/p>\n
\u2013 Compatible with entire line of 55x rifles, including 556, 556R, 556XI, and 551-A1, 550, 551, 553, 751.<\/p>\n
\u2013 Made in the USA.\u00a0 Sear and Hammer count as 2 parts towards 922R compliance.<\/p>\n
NOTE CHANGES TO THE POSTED INSTRUCTIONS. This Gen II design is 556XI compatible:<\/p>\n
1. It no longer includes the hammer spring.\u00a0 Instead the SIG hammer spring is re-used.<\/p>\n
2.\u00a0 It no longer includes the teflon spacer.<\/p>\n
3.\u00a0 The sear spring is now used IN ADDITION TO the SIG sear spring.<\/p>\n
The included instructions have been modified to reflect these changes, however the posted pdf guide and the website pictures have not been updated yet, so there might be some differences versus what is presented.<\/p>\n
SIG 556 Trigger Install<\/a><\/p>\n